linux.git/Documentation/admin-guide/mm, branch v5.8

doc: THP CoW fault no longer allocate THP

2020-06-26T07:27:37+00:00

Since commit 3917c80280c9 ("thp: change CoW semantics for anon-THP"),
THP CoW page fault is rewritten.  Now it just splits pmd then fallback
to base page fault, it doesn't try to allocate THP anymore.  So it is no
longer counted in THP_FAULT_ALLOC.

Remove the obsolete statement in documentation about THP CoW allocation
to avoid confusion.

Link: http://lkml.kernel.org/r/1592424895-5421-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi 
Cc: Kirill A. Shutemov 
Cc: Zi Yan 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mmap locking API: convert mmap_sem comments

2020-06-09T16:39:14+00:00

Convert comments that reference mmap_sem to reference mmap_lock instead.

[akpm@linux-foundation.org: fix up linux-next leftovers]
[akpm@linux-foundation.org: s/lockaphore/lock/, per Vlastimil]
[akpm@linux-foundation.org: more linux-next fixups, per Michel]

Signed-off-by: Michel Lespinasse 
Signed-off-by: Andrew Morton 
Reviewed-by: Vlastimil Babka 
Reviewed-by: Daniel Jordan 
Cc: Davidlohr Bueso 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Jason Gunthorpe 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Laurent Dufour 
Cc: Liam Howlett 
Cc: Matthew Wilcox 
Cc: Peter Zijlstra 
Cc: Ying Han 
Link: http://lkml.kernel.org/r/20200520052908.204642-13-walken@google.com
Signed-off-by: Linus Torvalds

hugetlbfs: clean up command line processing

2020-06-04T03:09:46+00:00

With all hugetlb page processing done in a single file clean up code.

- Make code match desired semantics
  - Update documentation with semantics
- Make all warnings and errors messages start with 'HugeTLB:'.
- Consistently name command line parsing routines.
- Warn if !hugepages_supported() and command line parameters have
  been specified.
- Add comments to code
  - Describe some of the subtle interactions
  - Describe semantics of command line arguments

This patch also fixes issues with implicitly setting the number of
gigantic huge pages to preallocate.  Previously on X86 command line,

        hugepages=2 default_hugepagesz=1G

would result in zero 1G pages being preallocated and,

        # grep HugePages_Total /proc/meminfo
        HugePages_Total:       0
        # sysctl -a | grep nr_hugepages
        vm.nr_hugepages = 2
        vm.nr_hugepages_mempolicy = 2
        # cat /proc/sys/vm/nr_hugepages
        2

After this patch 2 gigantic pages will be preallocated and all the proc,
sysfs, sysctl and meminfo files will accurately reflect this.

To address the issue with gigantic pages, a small change in behavior was
made to command line processing.  Previously the command line,

        hugepages=128 default_hugepagesz=2M hugepagesz=2M hugepages=256

would result in the allocation of 256 2M huge pages.  The value 128 would
be ignored without any warning.  After this patch, 128 2M pages will be
allocated and a warning message will be displayed indicating the value of
256 is ignored.  This change in behavior is required because allocation of
implicitly specified gigantic pages must be done when the
default_hugepagesz= is encountered for gigantic pages.  Previously the
code waited until later in the boot process (hugetlb_init), to allocate
pages of default size.  However the bootmem allocator required for
gigantic allocations is not available at this time.

Signed-off-by: Mike Kravetz 
Signed-off-by: Andrew Morton 
Tested-by: Sandipan Das 
Acked-by: Gerald Schaefer 	[s390]
Acked-by: Will Deacon 
Cc: Albert Ou 
Cc: Benjamin Herrenschmidt 
Cc: Catalin Marinas 
Cc: Christian Borntraeger 
Cc: Christophe Leroy 
Cc: Dave Hansen 
Cc: David S. Miller 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Longpeng 
Cc: Mina Almasry 
Cc: Nitesh Narayan Lal 
Cc: Palmer Dabbelt 
Cc: Paul Mackerras 
Cc: Paul Walmsley 
Cc: Peter Xu 
Cc: Randy Dunlap 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Anders Roxell 
Cc: "Aneesh Kumar K.V" 
Cc: Qian Cai 
Cc: Stephen Rothwell 
Link: http://lkml.kernel.org/r/20200417185049.275845-5-mike.kravetz@oracle.com
Signed-off-by: Linus Torvalds

khugepaged: introduce 'max_ptes_shared' tunable

2020-06-04T03:09:46+00:00

'max_ptes_shared' specifies how many pages can be shared across multiple
processes.  Exceeding the number would block the collapse::

	/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_shared

A higher value may increase memory footprint for some workloads.

By default, at least half of pages has to be not shared.

[colin.king@canonical.com: fix several spelling mistakes]
  Link: http://lkml.kernel.org/r/20200420084241.65433-1-colin.king@canonical.com
Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Colin Ian King 
Signed-off-by: Andrew Morton 
Tested-by: Zi Yan 
Reviewed-by: William Kucharski 
Reviewed-by: Zi Yan 
Acked-by: Yang Shi 
Cc: Andrea Arcangeli 
Cc: John Hubbard 
Cc: Mike Kravetz 
Cc: Ralph Campbell 
Link: http://lkml.kernel.org/r/20200416160026.16538-9-kirill.shutemov@linux.intel.com
Signed-off-by: Linus Torvalds

docs: mm: userfaultfd.rst: use a cross-reference for a section

2020-04-20T21:45:23+00:00

Instead of using "foo", let's use `foo`_, with is a ReST way of
saying that foo is a section of the document. With that, after
building the docs, an hyperlink is generated.

Signed-off-by: Mauro Carvalho Chehab 
Link: https://lore.kernel.org/r/f46b45f1aaec233217f2e0b0438bbd8cc16fe17b.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet

docs: mm: userfaultfd.rst: use ``foo`` for literals

2020-04-20T21:45:23+00:00

Several parts of this document define literals: ioctl names,
function calls, directory patches, etc. Mark those as literal
blocks, in order to improve its readability (both at text mode
and after parsed by Sphinx.

This fixes those two warnings:

	Documentation/admin-guide/mm/userfaultfd.rst:139: WARNING: Inline emphasis start-string without end-string.
	Documentation/admin-guide/mm/userfaultfd.rst:139: WARNING: Inline emphasis start-string without end-string.

produced during documentation build.

Signed-off-by: Mauro Carvalho Chehab 
Link: https://lore.kernel.org/r/2ae061761baf8fe00cdf8a7e6dae293756849a05.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet

userfaultfd: wp: UFFDIO_REGISTER_MODE_WP documentation update

2020-04-07T17:43:39+00:00

Add documentation about the write protection support.

[peterx@redhat.com: rewrite in rst format; fixups here and there]
Signed-off-by: Martin Cracauer 
Signed-off-by: Andrea Arcangeli 
Signed-off-by: Peter Xu 
Signed-off-by: Andrew Morton 
Reviewed-by: Jerome Glisse 
Reviewed-by: Mike Rapoport 
Cc: Bobby Powers 
Cc: Brian Geffon 
Cc: David Hildenbrand 
Cc: Denis Plotnikov 
Cc: "Dr . David Alan Gilbert" 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: "Kirill A . Shutemov" 
Cc: Marty McFadden 
Cc: Maya Gokhale 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Pavel Emelyanov 
Cc: Rik van Riel 
Cc: Shaohua Li 
Link: http://lkml.kernel.org/r/20200220163112.11409-17-peterx@redhat.com
Signed-off-by: Linus Torvalds

mm, thp: track fallbacks due to failed memcg charges separately

2020-04-07T17:43:38+00:00

The thp_fault_fallback and thp_file_fallback vmstats are incremented if
either the hugepage allocation fails through the page allocator or the
hugepage charge fails through mem cgroup.

This patch leaves this field untouched but adds two new fields,
thp_{fault,file}_fallback_charge, which is incremented only when the mem
cgroup charge fails.

This distinguishes between attempted hugepage allocations that fail due to
fragmentation (or low memory conditions) and those that fail due to mem
cgroup limits.  That can be used to determine the impact of fragmentation
on the system by excluding faults that failed due to memcg usage.

Signed-off-by: David Rientjes 
Signed-off-by: Andrew Morton 
Reviewed-by: Yang Shi 
Acked-by: Kirill A. Shutemov 
Cc: Mike Rapoport 
Cc: Jeremy Cline 
Cc: Andrea Arcangeli 
Cc: Mike Kravetz 
Cc: Michal Hocko 
Cc: Vlastimil Babka 
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061422070.7412@chino.kir.corp.google.com
Signed-off-by: Linus Torvalds

mm, shmem: add vmstat for hugepage fallback

2020-04-07T17:43:38+00:00

The existing thp_fault_fallback indicates when thp attempts to allocate a
hugepage but fails, or if the hugepage cannot be charged to the mem cgroup
hierarchy.

Extend this to shmem as well.  Adds a new thp_file_fallback to complement
thp_file_alloc that gets incremented when a hugepage is attempted to be
allocated but fails, or if it cannot be charged to the mem cgroup
hierarchy.

Additionally, remove the check for CONFIG_TRANSPARENT_HUGE_PAGECACHE from
shmem_alloc_hugepage() since it is only called with this configuration
option.

Signed-off-by: David Rientjes 
Signed-off-by: Andrew Morton 
Reviewed-by: Yang Shi 
Acked-by: Kirill A. Shutemov 
Cc: Mike Rapoport 
Cc: Jeremy Cline 
Cc: Andrea Arcangeli 
Cc: Mike Kravetz 
Cc: Michal Hocko 
Cc: Vlastimil Babka 
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061421240.7412@chino.kir.corp.google.com
Signed-off-by: Linus Torvalds

docs/vm: transhuge: fix typo in madvise reference

2019-07-22T20:45:12+00:00

Fix an off-by-one typo in the transparent huge pages admin
documentation.

Signed-off-by: Jeremy Cline 
Acked-by: Mike Rapoport 
Signed-off-by: Jonathan Corbet