linux.git/Documentation/admin-guide/mm, branch v5.17

proc: fix documentation and description of pagemap

2022-03-05T19:08:33+00:00

Since bit 57 was exported for uffd-wp write-protected (commit
fb8e37f35a2f: "mm/pagemap: export uffd-wp protection information"),
fixing it can reduce some unnecessary confusion.

Link: https://lkml.kernel.org/r/20220301044538.3042713-1-yun.zhou@windriver.com
Fixes: fb8e37f35a2fe1 ("mm/pagemap: export uffd-wp protection information")
Signed-off-by: Yun Zhou 
Reviewed-by: Peter Xu 
Cc: Jonathan Corbet 
Cc: Tiberiu A Georgescu 
Cc: Florian Schmidt 
Cc: Ivan Teterevkov 
Cc: SeongJae Park 
Cc: Yang Shi 
Cc: David Hildenbrand 
Cc: Axel Rasmussen 
Cc: Miaohe Lin 
Cc: Andrea Arcangeli 
Cc: Colin Cross 
Cc: Alistair Popple 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/usage: update for schemes statistics

2022-01-15T14:30:33+00:00

This updates DAMON debugfs interface for statistics of schemes
successfully applied regions and time/space quota limit exceeds counts.

Link: https://lkml.kernel.org/r/20211210150016.35349-7-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/reclaim: document statistics parameters

2022-01-15T14:30:33+00:00

This adds descriptions for the DAMON_RECLAIM statistics parameters.

Link: https://lkml.kernel.org/r/20211210150016.35349-5-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/usage: update for kdamond_pid and (mk|rm)_contexts

2022-01-15T14:30:32+00:00

The DAMON debugfs usage document is missing descriptions for
'kdamond_pid', 'mk_contexts', and 'rm_contexts' debugfs files.  This
commit adds those.

Link: https://lkml.kernel.org/r/20211209131806.19317-6-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/usage: mention tracepoint at the beginning

2022-01-15T14:30:32+00:00

To get detailed monitoring results from the user space, users need to
use the damon_aggregated tracepoint.  This commit adds a brief mention
of it at the beginning of the usage document.

Link: https://lkml.kernel.org/r/20211209131806.19317-5-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/usage: remove redundant information

2022-01-15T14:30:32+00:00

DAMON usage document mentions DAMON user space tool and programming
interface twice.  This commit integrates those and remove unnecessary
part.

Link: https://lkml.kernel.org/r/20211209131806.19317-4-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/usage: update for scheme quotas and watermarks

2022-01-15T14:30:32+00:00

DAMOS features including time/space quota limits and watermarks are not
described in the DAMON debugfs interface document.  This commit updates
the document for the features.

Link: https://lkml.kernel.org/r/20211209131806.19317-3-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/mempolicy: add set_mempolicy_home_node syscall

2022-01-15T14:30:30+00:00

This syscall can be used to set a home node for the MPOL_BIND and
MPOL_PREFERRED_MANY memory policy.  Users should use this syscall after
setting up a memory policy for the specified range as shown below.

  mbind(p, nr_pages * page_size, MPOL_BIND, new_nodes->maskp,
        new_nodes->size + 1, 0);
  sys_set_mempolicy_home_node((unsigned long)p, nr_pages * page_size,
				home_node, 0);

The syscall allows specifying a home node/preferred node from which
kernel will fulfill memory allocation requests first.

For address range with MPOL_BIND memory policy, if nodemask specifies
more than one node, page allocations will come from the node in the
nodemask with sufficient free memory that is closest to the home
node/preferred node.

For MPOL_PREFERRED_MANY if the nodemask specifies more than one node,
page allocation will come from the node in the nodemask with sufficient
free memory that is closest to the home node/preferred node.  If there
is not enough memory in all the nodes specified in the nodemask, the
allocation will be attempted from the closest numa node to the home node
in the system.

This helps applications to hint at a memory allocation preference node
and fallback to _only_ a set of nodes if the memory is not available on
the preferred node.  Fallback allocation is attempted from the node
which is nearest to the preferred node.

This helps applications to have control on memory allocation numa nodes
and avoids default fallback to slow memory NUMA nodes.  For example a
system with NUMA nodes 1,2 and 3 with DRAM memory and 10, 11 and 12 of
slow memory

 new_nodes = numa_bitmask_alloc(nr_nodes);

 numa_bitmask_setbit(new_nodes, 1);
 numa_bitmask_setbit(new_nodes, 2);
 numa_bitmask_setbit(new_nodes, 3);

 p = mmap(NULL, nr_pages * page_size, protflag, mapflag, -1, 0);
 mbind(p, nr_pages * page_size, MPOL_BIND, new_nodes->maskp,  new_nodes->size + 1, 0);

 sys_set_mempolicy_home_node(p, nr_pages * page_size, 2, 0);

This will allocate from nodes closer to node 2 and will make sure the
kernel will only allocate from nodes 1, 2, and 3.  Memory will not be
allocated from slow memory nodes 10, 11, and 12.  This differs from
default MPOL_BIND behavior in that with default MPOL_BIND the allocation
will be attempted from node closer to the local node.  One of the
reasons to specify a home node is to allow allocations from cpu less
NUMA node and its nearby NUMA nodes.

With MPOL_PREFERRED_MANY on the other hand will first try to allocate
from the closest node to node 2 from the node list 1, 2 and 3.  If those
nodes don't have enough memory, kernel will allocate from slow memory
node 10, 11 and 12 which ever is closer to node 2.

Link: https://lkml.kernel.org/r/20211202123810.267175-3-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Cc: Ben Widawsky 
Cc: Dave Hansen 
Cc: Feng Tang 
Cc: Michal Hocko 
Cc: Andrea Arcangeli 
Cc: Mel Gorman 
Cc: Mike Kravetz 
Cc: Randy Dunlap 
Cc: Vlastimil Babka 
Cc: Andi Kleen 
Cc: Dan Williams 
Cc: Huang Ying 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions

2021-11-06T20:30:46+00:00

Some descriptions of page flags in 'pagemap.rst' are written in
assumption of none-rst, which respects every new line, as below:

    7 - SLAB
       page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
       When compound page is used, SLUB/SLQB will only set this flag on the head

Because rst ignores the new line between the first sentence and second
sentence, resulting html looks a little bit weird, as below.

    7 - SLAB
    page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator When
                                                                       ^
    compound page is used, SLUB/SLQB will only set this flag on the head
    page; SLOB will not flag it at all.

This change makes it more natural and consistent with other parts in the
rendered version.

Link: https://lkml.kernel.org/r/20211022090311.3856-5-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Cc: Peter Xu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Docs/admin-guide/mm/damon/start: simplify the content

2021-11-06T20:30:46+00:00

Information in 'TL; DR' section of 'Getting Started' is duplicated in
other parts of the doc.  It is also asking readers to visit the access
pattern visualizations gallery web site to show the results of example
visualization commands, while the users of the commands can use terminal
output.

To make the doc simple, this removes the duplicated 'TL; DR' section and
replaces the visualization example commands with versions using terminal
outputs.

Link: https://lkml.kernel.org/r/20211022090311.3856-4-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Cc: Peter Xu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds