linux.git/mm/huge_memory.c, branch v6.11 Linux kernel source tree mm/numa: no task_numa_fault() call if PMD is changed 2024-08-16T05:16:15+00:00 Zi Yan ziy@nvidia.com 2024-08-09T14:59:05+00:00 fd8c35a92910f4829b7c99841f39b1b952c259d5 When handling a numa page fault, task_numa_fault() should be called by a process that restores the page table of the faulted folio to avoid duplicated stats counting. Commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault handling") restructured do_huge_pmd_numa_page() and did not avoid task_numa_fault() call in the second page table check after a numa migration failure. Fix it by making all !pmd_same() return immediately. This issue can cause task_numa_fault() being called more than necessary and lead to unexpected numa balancing results (It is hard to tell whether the issue will cause positive or negative performance impact due to duplicated numa fault counting). Link: https://lkml.kernel.org/r/20240809145906.1513458-3-ziy@nvidia.com Fixes: c5b5a3dd2c1f ("mm: thp: refactor NUMA fault handling") Reported-by: "Huang, Ying" <ying.huang@intel.com> Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/ Signed-off-by: Zi Yan <ziy@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Yang Shi <shy828301@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
When handling a numa page fault, task_numa_fault() should be called by a
process that restores the page table of the faulted folio to avoid
duplicated stats counting.  Commit c5b5a3dd2c1f ("mm: thp: refactor NUMA
fault handling") restructured do_huge_pmd_numa_page() and did not avoid
task_numa_fault() call in the second page table check after a numa
migration failure.  Fix it by making all !pmd_same() return immediately.

This issue can cause task_numa_fault() being called more than necessary
and lead to unexpected numa balancing results (It is hard to tell whether
the issue will cause positive or negative performance impact due to
duplicated numa fault counting).

Link: https://lkml.kernel.org/r/20240809145906.1513458-3-ziy@nvidia.com
Fixes: c5b5a3dd2c1f ("mm: thp: refactor NUMA fault handling")
Reported-by: "Huang, Ying" <ying.huang@intel.com>
Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/huge_memory: avoid PMD-size page cache if needed 2024-07-26T21:33:09+00:00 Gavin Shan gshan@redhat.com 2024-07-15T00:04:23+00:00 d659b715e94ac039803d7601505d3473393fc0be xarray can't support arbitrary page cache size. the largest and supported page cache size is defined as MAX_PAGECACHE_ORDER by commit 099d90642a71 ("mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray"). However, it's possible to have 512MB page cache in the huge memory's collapsing path on ARM64 system whose base page size is 64KB. 512MB page cache is breaking the limitation and a warning is raised when the xarray entry is split as shown in the following example. [root@dhcp-10-26-1-207 ~]# cat /proc/1/smaps | grep KernelPageSize KernelPageSize: 64 kB [root@dhcp-10-26-1-207 ~]# cat /tmp/test.c : int main(int argc, char **argv) { const char *filename = TEST_XFS_FILENAME; int fd = 0; void *buf = (void *)-1, *p; int pgsize = getpagesize(); int ret = 0; if (pgsize != 0x10000) { fprintf(stdout, "System with 64KB base page size is required!\n"); return -EPERM; } system("echo 0 > /sys/devices/virtual/bdi/253:0/read_ahead_kb"); system("echo 1 > /proc/sys/vm/drop_caches"); /* Open the xfs file */ fd = open(filename, O_RDONLY); assert(fd > 0); /* Create VMA */ buf = mmap(NULL, TEST_MEM_SIZE, PROT_READ, MAP_SHARED, fd, 0); assert(buf != (void *)-1); fprintf(stdout, "mapped buffer at 0x%p\n", buf); /* Populate VMA */ ret = madvise(buf, TEST_MEM_SIZE, MADV_NOHUGEPAGE); assert(ret == 0); ret = madvise(buf, TEST_MEM_SIZE, MADV_POPULATE_READ); assert(ret == 0); /* Collapse VMA */ ret = madvise(buf, TEST_MEM_SIZE, MADV_HUGEPAGE); assert(ret == 0); ret = madvise(buf, TEST_MEM_SIZE, MADV_COLLAPSE); if (ret) { fprintf(stdout, "Error %d to madvise(MADV_COLLAPSE)\n", errno); goto out; } /* Split xarray entry. Write permission is needed */ munmap(buf, TEST_MEM_SIZE); buf = (void *)-1; close(fd); fd = open(filename, O_RDWR); assert(fd > 0); fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, TEST_MEM_SIZE - pgsize, pgsize); out: if (buf != (void *)-1) munmap(buf, TEST_MEM_SIZE); if (fd > 0) close(fd); return ret; } [root@dhcp-10-26-1-207 ~]# gcc /tmp/test.c -o /tmp/test [root@dhcp-10-26-1-207 ~]# /tmp/test ------------[ cut here ]------------ WARNING: CPU: 25 PID: 7560 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128 Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib \ nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct \ nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \ ip_set rfkill nf_tables nfnetlink vfat fat virtio_balloon drm fuse \ xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 virtio_net \ sha1_ce net_failover virtio_blk virtio_console failover dimlib virtio_mmio CPU: 25 PID: 7560 Comm: test Kdump: loaded Not tainted 6.10.0-rc7-gavin+ #9 Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : xas_split_alloc+0xf8/0x128 lr : split_huge_page_to_list_to_order+0x1c4/0x780 sp : ffff8000ac32f660 x29: ffff8000ac32f660 x28: ffff0000e0969eb0 x27: ffff8000ac32f6c0 x26: 0000000000000c40 x25: ffff0000e0969eb0 x24: 000000000000000d x23: ffff8000ac32f6c0 x22: ffffffdfc0700000 x21: 0000000000000000 x20: 0000000000000000 x19: ffffffdfc0700000 x18: 0000000000000000 x17: 0000000000000000 x16: ffffd5f3708ffc70 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: ffffffffffffffc0 x10: 0000000000000040 x9 : ffffd5f3708e692c x8 : 0000000000000003 x7 : 0000000000000000 x6 : ffff0000e0969eb8 x5 : ffffd5f37289e378 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 000000000000000d x1 : 000000000000000c x0 : 0000000000000000 Call trace: xas_split_alloc+0xf8/0x128 split_huge_page_to_list_to_order+0x1c4/0x780 truncate_inode_partial_folio+0xdc/0x160 truncate_inode_pages_range+0x1b4/0x4a8 truncate_pagecache_range+0x84/0xa0 xfs_flush_unmap_range+0x70/0x90 [xfs] xfs_file_fallocate+0xfc/0x4d8 [xfs] vfs_fallocate+0x124/0x2f0 ksys_fallocate+0x4c/0xa0 __arm64_sys_fallocate+0x24/0x38 invoke_syscall.constprop.0+0x7c/0xd8 do_el0_svc+0xb4/0xd0 el0_svc+0x44/0x1d8 el0t_64_sync_handler+0x134/0x150 el0t_64_sync+0x17c/0x180 Fix it by correcting the supported page cache orders, different sets for DAX and other files. With it corrected, 512MB page cache becomes disallowed on all non-DAX files on ARM64 system where the base page size is 64KB. After this patch is applied, the test program fails with error -EINVAL returned from __thp_vma_allowable_orders() and the madvise() system call to collapse the page caches. Link: https://lkml.kernel.org/r/20240715000423.316491-1-gshan@redhat.com Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache") Signed-off-by: Gavin Shan <gshan@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Zi Yan <ziy@nvidia.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Barry Song <baohua@kernel.org> Cc: Don Dutile <ddutile@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: William Kucharski <william.kucharski@oracle.com> Cc: <stable@vger.kernel.org> [5.17+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
xarray can't support arbitrary page cache size.  the largest and supported
page cache size is defined as MAX_PAGECACHE_ORDER by commit 099d90642a71
("mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray").  However,
it's possible to have 512MB page cache in the huge memory's collapsing
path on ARM64 system whose base page size is 64KB.  512MB page cache is
breaking the limitation and a warning is raised when the xarray entry is
split as shown in the following example.

[root@dhcp-10-26-1-207 ~]# cat /proc/1/smaps | grep KernelPageSize
KernelPageSize:       64 kB
[root@dhcp-10-26-1-207 ~]# cat /tmp/test.c
   :
int main(int argc, char **argv)
{
	const char *filename = TEST_XFS_FILENAME;
	int fd = 0;
	void *buf = (void *)-1, *p;
	int pgsize = getpagesize();
	int ret = 0;

	if (pgsize != 0x10000) {
		fprintf(stdout, "System with 64KB base page size is required!\n");
		return -EPERM;
	}

	system("echo 0 > /sys/devices/virtual/bdi/253:0/read_ahead_kb");
	system("echo 1 > /proc/sys/vm/drop_caches");

	/* Open the xfs file */
	fd = open(filename, O_RDONLY);
	assert(fd > 0);

	/* Create VMA */
	buf = mmap(NULL, TEST_MEM_SIZE, PROT_READ, MAP_SHARED, fd, 0);
	assert(buf != (void *)-1);
	fprintf(stdout, "mapped buffer at 0x%p\n", buf);

	/* Populate VMA */
	ret = madvise(buf, TEST_MEM_SIZE, MADV_NOHUGEPAGE);
	assert(ret == 0);
	ret = madvise(buf, TEST_MEM_SIZE, MADV_POPULATE_READ);
	assert(ret == 0);

	/* Collapse VMA */
	ret = madvise(buf, TEST_MEM_SIZE, MADV_HUGEPAGE);
	assert(ret == 0);
	ret = madvise(buf, TEST_MEM_SIZE, MADV_COLLAPSE);
	if (ret) {
		fprintf(stdout, "Error %d to madvise(MADV_COLLAPSE)\n", errno);
		goto out;
	}

	/* Split xarray entry. Write permission is needed */
	munmap(buf, TEST_MEM_SIZE);
	buf = (void *)-1;
	close(fd);
	fd = open(filename, O_RDWR);
	assert(fd > 0);
	fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
 		  TEST_MEM_SIZE - pgsize, pgsize);
out:
	if (buf != (void *)-1)
		munmap(buf, TEST_MEM_SIZE);
	if (fd > 0)
		close(fd);

	return ret;
}

[root@dhcp-10-26-1-207 ~]# gcc /tmp/test.c -o /tmp/test
[root@dhcp-10-26-1-207 ~]# /tmp/test
 ------------[ cut here ]------------
 WARNING: CPU: 25 PID: 7560 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128
 Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib    \
 nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct      \
 nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4      \
 ip_set rfkill nf_tables nfnetlink vfat fat virtio_balloon drm fuse   \
 xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 virtio_net  \
 sha1_ce net_failover virtio_blk virtio_console failover dimlib virtio_mmio
 CPU: 25 PID: 7560 Comm: test Kdump: loaded Not tainted 6.10.0-rc7-gavin+ #9
 Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024
 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
 pc : xas_split_alloc+0xf8/0x128
 lr : split_huge_page_to_list_to_order+0x1c4/0x780
 sp : ffff8000ac32f660
 x29: ffff8000ac32f660 x28: ffff0000e0969eb0 x27: ffff8000ac32f6c0
 x26: 0000000000000c40 x25: ffff0000e0969eb0 x24: 000000000000000d
 x23: ffff8000ac32f6c0 x22: ffffffdfc0700000 x21: 0000000000000000
 x20: 0000000000000000 x19: ffffffdfc0700000 x18: 0000000000000000
 x17: 0000000000000000 x16: ffffd5f3708ffc70 x15: 0000000000000000
 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
 x11: ffffffffffffffc0 x10: 0000000000000040 x9 : ffffd5f3708e692c
 x8 : 0000000000000003 x7 : 0000000000000000 x6 : ffff0000e0969eb8
 x5 : ffffd5f37289e378 x4 : 0000000000000000 x3 : 0000000000000c40
 x2 : 000000000000000d x1 : 000000000000000c x0 : 0000000000000000
 Call trace:
  xas_split_alloc+0xf8/0x128
  split_huge_page_to_list_to_order+0x1c4/0x780
  truncate_inode_partial_folio+0xdc/0x160
  truncate_inode_pages_range+0x1b4/0x4a8
  truncate_pagecache_range+0x84/0xa0
  xfs_flush_unmap_range+0x70/0x90 [xfs]
  xfs_file_fallocate+0xfc/0x4d8 [xfs]
  vfs_fallocate+0x124/0x2f0
  ksys_fallocate+0x4c/0xa0
  __arm64_sys_fallocate+0x24/0x38
  invoke_syscall.constprop.0+0x7c/0xd8
  do_el0_svc+0xb4/0xd0
  el0_svc+0x44/0x1d8
  el0t_64_sync_handler+0x134/0x150
  el0t_64_sync+0x17c/0x180

Fix it by correcting the supported page cache orders, different sets for
DAX and other files.  With it corrected, 512MB page cache becomes
disallowed on all non-DAX files on ARM64 system where the base page size
is 64KB.  After this patch is applied, the test program fails with error
-EINVAL returned from __thp_vma_allowable_orders() and the madvise()
system call to collapse the page caches.

Link: https://lkml.kernel.org/r/20240715000423.316491-1-gshan@redhat.com
Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache")
Signed-off-by: Gavin Shan <gshan@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: <stable@vger.kernel.org>	[5.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: huge_memory: use !CONFIG_64BIT to relax huge page alignment on 32 bit machines 2024-07-26T21:33:09+00:00 Yang Shi yang@os.amperecomputing.com 2024-07-12T15:58:55+00:00 d9592025000b3cf26c742f3505da7b83aedc26d5 Yves-Alexis Perez reported commit 4ef9ad19e176 ("mm: huge_memory: don't force huge page alignment on 32 bit") didn't work for x86_32 [1]. It is because x86_32 uses CONFIG_X86_32 instead of CONFIG_32BIT. !CONFIG_64BIT should cover all 32 bit machines. [1] https://lore.kernel.org/linux-mm/CAHbLzkr1LwH3pcTgM+aGQ31ip2bKqiqEQ8=FQB+t2c3dhNKNHA@mail.gmail.com/ Link: https://lkml.kernel.org/r/20240712155855.1130330-1-yang@os.amperecomputing.com Fixes: 4ef9ad19e176 ("mm: huge_memory: don't force huge page alignment on 32 bit") Signed-off-by: Yang Shi <yang@os.amperecomputing.com> Reported-by: Yves-Alexis Perez <corsac@debian.org> Tested-by: Yves-Alexis Perez <corsac@debian.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Salvatore Bonaccorso <carnil@debian.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: <stable@vger.kernel.org> [6.8+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Yves-Alexis Perez reported commit 4ef9ad19e176 ("mm: huge_memory: don't
force huge page alignment on 32 bit") didn't work for x86_32 [1].  It is
because x86_32 uses CONFIG_X86_32 instead of CONFIG_32BIT.

!CONFIG_64BIT should cover all 32 bit machines.

[1] https://lore.kernel.org/linux-mm/CAHbLzkr1LwH3pcTgM+aGQ31ip2bKqiqEQ8=FQB+t2c3dhNKNHA@mail.gmail.com/

Link: https://lkml.kernel.org/r/20240712155855.1130330-1-yang@os.amperecomputing.com
Fixes: 4ef9ad19e176 ("mm: huge_memory: don't force huge page alignment on 32 bit")
Signed-off-by: Yang Shi <yang@os.amperecomputing.com>
Reported-by: Yves-Alexis Perez <corsac@debian.org>
Tested-by: Yves-Alexis Perez <corsac@debian.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Salvatore Bonaccorso <carnil@debian.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>	[6.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: shmem: rename mTHP shmem counters 2024-07-12T22:52:23+00:00 Ryan Roberts ryan.roberts@arm.com 2024-07-10T09:55:01+00:00 63d9866ab01ffd0d0835d5564107283a4afc0a38 The legacy PMD-sized THP counters at /proc/vmstat include thp_file_alloc, thp_file_fallback and thp_file_fallback_charge, which rather confusingly refer to shmem THP and do not include any other types of file pages. This is inconsistent since in most other places in the kernel, THP counters are explicitly separated for anon, shmem and file flavours. However, we are stuck with it since it constitutes a user ABI. Recently, commit 66f44583f9b6 ("mm: shmem: add mTHP counters for anonymous shmem") added equivalent mTHP stats for shmem, keeping the same "file_" prefix in the names. But in future, we may want to add extra stats to cover actual file pages, at which point, it would all become very confusing. So let's take the opportunity to rename these new counters "shmem_" before the change makes it upstream and the ABI becomes immutable. While we are at it, let's improve the documentation for the legacy counters to make it clear that they count shmem pages only. Link: https://lkml.kernel.org/r/20240710095503.3193901-1-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Lance Yang <ioworker0@gmail.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Daniel Gomez <da.gomez@samsung.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
The legacy PMD-sized THP counters at /proc/vmstat include thp_file_alloc,
thp_file_fallback and thp_file_fallback_charge, which rather confusingly
refer to shmem THP and do not include any other types of file pages.  This
is inconsistent since in most other places in the kernel, THP counters are
explicitly separated for anon, shmem and file flavours.  However, we are
stuck with it since it constitutes a user ABI.

Recently, commit 66f44583f9b6 ("mm: shmem: add mTHP counters for anonymous
shmem") added equivalent mTHP stats for shmem, keeping the same "file_"
prefix in the names.  But in future, we may want to add extra stats to
cover actual file pages, at which point, it would all become very
confusing.

So let's take the opportunity to rename these new counters "shmem_" before
the change makes it upstream and the ABI becomes immutable.  While we are
at it, let's improve the documentation for the legacy counters to make it
clear that they count shmem pages only.

Link: https://lkml.kernel.org/r/20240710095503.3193901-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem 2024-07-12T22:52:21+00:00 Bang Li libang.li@antgroup.com 2024-07-05T03:23:09+00:00 26c7d8413aaf113a54b54f63e151416a5c5c2a88 After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for anonymous shmem"), we can configure different policies through the multi-size THP sysfs interface for anonymous shmem. But currently "THPeligible" indicates only whether the mapping is eligible for allocating THP-pages as well as the THP is PMD mappable or not for anonymous shmem, we need to support semantics for mTHP with anonymous shmem similar to those for mTHP with anonymous memory. Link: https://lkml.kernel.org/r/20240705032309.24933-1-libang.li@antgroup.com Signed-off-by: Bang Li <libang.li@antgroup.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Lance Yang <ioworker0@gmail.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for anonymous
shmem"), we can configure different policies through the multi-size THP
sysfs interface for anonymous shmem.  But currently "THPeligible"
indicates only whether the mapping is eligible for allocating THP-pages as
well as the THP is PMD mappable or not for anonymous shmem, we need to
support semantics for mTHP with anonymous shmem similar to those for mTHP
with anonymous memory.

Link: https://lkml.kernel.org/r/20240705032309.24933-1-libang.li@antgroup.com
Signed-off-by: Bang Li <libang.li@antgroup.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: fix khugepaged activation policy 2024-07-12T22:52:20+00:00 Ryan Roberts ryan.roberts@arm.com 2024-07-04T09:10:50+00:00 00f58104202c472e487f0866fbd38832523fd4f9 Since the introduction of mTHP, the docuementation has stated that khugepaged would be enabled when any mTHP size is enabled, and disabled when all mTHP sizes are disabled. There are 2 problems with this; 1. this is not what was implemented by the code and 2. this is not the desirable behavior. Desirable behavior is for khugepaged to be enabled when any PMD-sized THP is enabled, anon or file. (Note that file THP is still controlled by the top-level control so we must always consider that, as well as the PMD-size mTHP control for anon). khugepaged only supports collapsing to PMD-sized THP so there is no value in enabling it when PMD-sized THP is disabled. So let's change the code and documentation to reflect this policy. Further, per-size enabled control modification events were not previously forwarded to khugepaged to give it an opportunity to start or stop. Consequently the following was resulting in khugepaged eroneously not being activated: echo never > /sys/kernel/mm/transparent_hugepage/enabled echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled [ryan.roberts@arm.com: v3] Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20240704091051.2411934-1-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface") Closes: https://lore.kernel.org/linux-mm/7a0bbe69-1e3d-4263-b206-da007791a5c4@redhat.com/ Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Barry Song <baohua@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Lance Yang <ioworker0@gmail.com> Cc: Yang Shi <shy828301@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Since the introduction of mTHP, the docuementation has stated that
khugepaged would be enabled when any mTHP size is enabled, and disabled
when all mTHP sizes are disabled.  There are 2 problems with this; 1. 
this is not what was implemented by the code and 2.  this is not the
desirable behavior.

Desirable behavior is for khugepaged to be enabled when any PMD-sized THP
is enabled, anon or file.  (Note that file THP is still controlled by the
top-level control so we must always consider that, as well as the PMD-size
mTHP control for anon).  khugepaged only supports collapsing to PMD-sized
THP so there is no value in enabling it when PMD-sized THP is disabled. 
So let's change the code and documentation to reflect this policy.

Further, per-size enabled control modification events were not previously
forwarded to khugepaged to give it an opportunity to start or stop. 
Consequently the following was resulting in khugepaged eroneously not
being activated:

  echo never > /sys/kernel/mm/transparent_hugepage/enabled
  echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled

[ryan.roberts@arm.com: v3]
  Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20240704091051.2411934-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface")
Closes: https://lore.kernel.org/linux-mm/7a0bbe69-1e3d-4263-b206-da007791a5c4@redhat.com/
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: add per-order mTHP split counters 2024-07-12T22:52:13+00:00 Lance Yang ioworker0@gmail.com 2024-06-28T13:07:49+00:00 f216c845f3c772e54d27fe209fd300b10e7bf54a Patch series "mm: introduce per-order mTHP split counters", v3. At present, the split counters in THP statistics no longer include PTE-mapped mTHP. Therefore, we want to introduce per-order mTHP split counters to monitor the frequency of mTHP splits. This will assist developers in better analyzing and optimizing system performance. /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats split split_failed split_deferred This patch (of 2): Currently, the split counters in THP statistics no longer include PTE-mapped mTHP. Therefore, we propose introducing per-order mTHP split counters to monitor the frequency of mTHP splits. This will help developers better analyze and optimize system performance. /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats split split_failed split_deferred [ioworker0@gmail.com: make things more readable, per Barry and Baolin] Link: https://lkml.kernel.org/r/20240704012905.42971-2-ioworker0@gmail.com [ioworker0@gmail.com: use == for `order' test, per David] Link: https://lkml.kernel.org/r/20240705113119.82210-1-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240704012905.42971-1-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240704012905.42971-2-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240628130750.73097-1-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240628130750.73097-2-ioworker0@gmail.com Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com> Signed-off-by: Lance Yang <ioworker0@gmail.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Barry Song <baohua@kernel.org> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Bang Li <libang.li@antgroup.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Patch series "mm: introduce per-order mTHP split counters", v3.

At present, the split counters in THP statistics no longer include
PTE-mapped mTHP.  Therefore, we want to introduce per-order mTHP split
counters to monitor the frequency of mTHP splits.  This will assist
developers in better analyzing and optimizing system performance.

/sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats
        split
        split_failed
        split_deferred


This patch (of 2):

Currently, the split counters in THP statistics no longer include
PTE-mapped mTHP.  Therefore, we propose introducing per-order mTHP split
counters to monitor the frequency of mTHP splits.  This will help
developers better analyze and optimize system performance.

/sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats
        split
        split_failed
        split_deferred

[ioworker0@gmail.com: make things more readable, per Barry and Baolin]
  Link: https://lkml.kernel.org/r/20240704012905.42971-2-ioworker0@gmail.com
[ioworker0@gmail.com: use == for `order' test, per David]
  Link: https://lkml.kernel.org/r/20240705113119.82210-1-ioworker0@gmail.com
Link: https://lkml.kernel.org/r/20240704012905.42971-1-ioworker0@gmail.com
Link: https://lkml.kernel.org/r/20240704012905.42971-2-ioworker0@gmail.com
Link: https://lkml.kernel.org/r/20240628130750.73097-1-ioworker0@gmail.com
Link: https://lkml.kernel.org/r/20240628130750.73097-2-ioworker0@gmail.com
Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com>
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Barry Song <baohua@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Bang Li <libang.li@antgroup.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Merge branch 'mm-hotfixes-stable' into mm-stable to pick up "mm: fix 2024-07-06T18:44:41+00:00 Andrew Morton akpm@linux-foundation.org 2024-07-06T18:44:41+00:00 8ef6fd0e9ea83a792ba53882ddc6e0d38ce0d636 crashes from deferred split racing folio migration", needed by "mm: migrate: split folio_migrate_mapping()". 
crashes from deferred split racing folio migration", needed by "mm:
migrate: split folio_migrate_mapping()".
mm: gup: stop abusing try_grab_folio 2024-07-06T18:39:51+00:00 Yang Shi yang@os.amperecomputing.com 2024-06-28T19:14:58+00:00 f442fa6141379a20b48ae3efabee827a3d260787 A kernel warning was reported when pinning folio in CMA memory when launching SEV virtual machine. The splat looks like: [ 464.325306] WARNING: CPU: 13 PID: 6734 at mm/gup.c:1313 __get_user_pages+0x423/0x520 [ 464.325464] CPU: 13 PID: 6734 Comm: qemu-kvm Kdump: loaded Not tainted 6.6.33+ #6 [ 464.325477] RIP: 0010:__get_user_pages+0x423/0x520 [ 464.325515] Call Trace: [ 464.325520] <TASK> [ 464.325523] ? __get_user_pages+0x423/0x520 [ 464.325528] ? __warn+0x81/0x130 [ 464.325536] ? __get_user_pages+0x423/0x520 [ 464.325541] ? report_bug+0x171/0x1a0 [ 464.325549] ? handle_bug+0x3c/0x70 [ 464.325554] ? exc_invalid_op+0x17/0x70 [ 464.325558] ? asm_exc_invalid_op+0x1a/0x20 [ 464.325567] ? __get_user_pages+0x423/0x520 [ 464.325575] __gup_longterm_locked+0x212/0x7a0 [ 464.325583] internal_get_user_pages_fast+0xfb/0x190 [ 464.325590] pin_user_pages_fast+0x47/0x60 [ 464.325598] sev_pin_memory+0xca/0x170 [kvm_amd] [ 464.325616] sev_mem_enc_register_region+0x81/0x130 [kvm_amd] Per the analysis done by yangge, when starting the SEV virtual machine, it will call pin_user_pages_fast(..., FOLL_LONGTERM, ...) to pin the memory. But the page is in CMA area, so fast GUP will fail then fallback to the slow path due to the longterm pinnalbe check in try_grab_folio(). The slow path will try to pin the pages then migrate them out of CMA area. But the slow path also uses try_grab_folio() to pin the page, it will also fail due to the same check then the above warning is triggered. In addition, the try_grab_folio() is supposed to be used in fast path and it elevates folio refcount by using add ref unless zero. We are guaranteed to have at least one stable reference in slow path, so the simple atomic add could be used. The performance difference should be trivial, but the misuse may be confusing and misleading. Redefined try_grab_folio() to try_grab_folio_fast(), and try_grab_page() to try_grab_folio(), and use them in the proper paths. This solves both the abuse and the kernel warning. The proper naming makes their usecase more clear and should prevent from abusing in the future. peterx said: : The user will see the pin fails, for gpu-slow it further triggers the WARN : right below that failure (as in the original report): : : folio = try_grab_folio(page, page_increm - 1, : foll_flags); : if (WARN_ON_ONCE(!folio)) { <------------------------ here : /* : * Release the 1st page ref if the : * folio is problematic, fail hard. : */ : gup_put_folio(page_folio(page), 1, : foll_flags); : ret = -EFAULT; : goto out; : } [1] https://lore.kernel.org/linux-mm/1719478388-31917-1-git-send-email-yangge1116@126.com/ [shy828301@gmail.com: fix implicit declaration of function try_grab_folio_fast] Link: https://lkml.kernel.org/r/CAHbLzkowMSso-4Nufc9hcMehQsK9PNz3OSu-+eniU-2Mm-xjhA@mail.gmail.com Link: https://lkml.kernel.org/r/20240628191458.2605553-1-yang@os.amperecomputing.com Fixes: 57edfcfd3419 ("mm/gup: accelerate thp gup even for "pages != NULL"") Signed-off-by: Yang Shi <yang@os.amperecomputing.com> Reported-by: yangge <yangge1116@126.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: <stable@vger.kernel.org> [6.6+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
A kernel warning was reported when pinning folio in CMA memory when
launching SEV virtual machine.  The splat looks like:

[  464.325306] WARNING: CPU: 13 PID: 6734 at mm/gup.c:1313 __get_user_pages+0x423/0x520
[  464.325464] CPU: 13 PID: 6734 Comm: qemu-kvm Kdump: loaded Not tainted 6.6.33+ #6
[  464.325477] RIP: 0010:__get_user_pages+0x423/0x520
[  464.325515] Call Trace:
[  464.325520]  <TASK>
[  464.325523]  ? __get_user_pages+0x423/0x520
[  464.325528]  ? __warn+0x81/0x130
[  464.325536]  ? __get_user_pages+0x423/0x520
[  464.325541]  ? report_bug+0x171/0x1a0
[  464.325549]  ? handle_bug+0x3c/0x70
[  464.325554]  ? exc_invalid_op+0x17/0x70
[  464.325558]  ? asm_exc_invalid_op+0x1a/0x20
[  464.325567]  ? __get_user_pages+0x423/0x520
[  464.325575]  __gup_longterm_locked+0x212/0x7a0
[  464.325583]  internal_get_user_pages_fast+0xfb/0x190
[  464.325590]  pin_user_pages_fast+0x47/0x60
[  464.325598]  sev_pin_memory+0xca/0x170 [kvm_amd]
[  464.325616]  sev_mem_enc_register_region+0x81/0x130 [kvm_amd]

Per the analysis done by yangge, when starting the SEV virtual machine, it
will call pin_user_pages_fast(..., FOLL_LONGTERM, ...) to pin the memory. 
But the page is in CMA area, so fast GUP will fail then fallback to the
slow path due to the longterm pinnalbe check in try_grab_folio().

The slow path will try to pin the pages then migrate them out of CMA area.
But the slow path also uses try_grab_folio() to pin the page, it will
also fail due to the same check then the above warning is triggered.

In addition, the try_grab_folio() is supposed to be used in fast path and
it elevates folio refcount by using add ref unless zero.  We are guaranteed
to have at least one stable reference in slow path, so the simple atomic add
could be used.  The performance difference should be trivial, but the
misuse may be confusing and misleading.

Redefined try_grab_folio() to try_grab_folio_fast(), and try_grab_page()
to try_grab_folio(), and use them in the proper paths.  This solves both
the abuse and the kernel warning.

The proper naming makes their usecase more clear and should prevent from
abusing in the future.

peterx said:

: The user will see the pin fails, for gpu-slow it further triggers the WARN
: right below that failure (as in the original report):
: 
:         folio = try_grab_folio(page, page_increm - 1,
:                                 foll_flags);
:         if (WARN_ON_ONCE(!folio)) { <------------------------ here
:                 /*
:                         * Release the 1st page ref if the
:                         * folio is problematic, fail hard.
:                         */
:                 gup_put_folio(page_folio(page), 1,
:                                 foll_flags);
:                 ret = -EFAULT;
:                 goto out;
:         }

[1] https://lore.kernel.org/linux-mm/1719478388-31917-1-git-send-email-yangge1116@126.com/

[shy828301@gmail.com: fix implicit declaration of function try_grab_folio_fast]
  Link: https://lkml.kernel.org/r/CAHbLzkowMSso-4Nufc9hcMehQsK9PNz3OSu-+eniU-2Mm-xjhA@mail.gmail.com
Link: https://lkml.kernel.org/r/20240628191458.2605553-1-yang@os.amperecomputing.com
Fixes: 57edfcfd3419 ("mm/gup: accelerate thp gup even for "pages != NULL"")
Signed-off-by: Yang Shi <yang@os.amperecomputing.com>
Reported-by: yangge <yangge1116@126.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>	[6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: refactor folio_undo_large_rmappable() 2024-07-05T01:05:50+00:00 Kefeng Wang wangkefeng.wang@huawei.com 2024-05-21T13:03:15+00:00 593a10dabe08dcf93259fce2badd8dc2528859a8 Folios of order <= 1 are not in deferred list, the check of order is added into folio_undo_large_rmappable() from commit 8897277acfef ("mm: support order-1 folios in the page cache"), but there is a repeated check for small folio (order 0) during each call of the folio_undo_large_rmappable(), so only keep folio_order() check inside the function. In addition, move all the checks into header file to save a function call for non-large-rmappable or empty deferred_list folio. Link: https://lkml.kernel.org/r/20240521130315.46072-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Lance Yang <ioworker0@gmail.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeel.butt@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Folios of order <= 1 are not in deferred list, the check of order is added
into folio_undo_large_rmappable() from commit 8897277acfef ("mm: support
order-1 folios in the page cache"), but there is a repeated check for
small folio (order 0) during each call of the
folio_undo_large_rmappable(), so only keep folio_order() check inside the
function.

In addition, move all the checks into header file to save a function call
for non-large-rmappable or empty deferred_list folio.

Link: https://lkml.kernel.org/r/20240521130315.46072-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>