Patch series "Rearrange batched folio freeing", v3.
Other than the obvious "remove calls to compound_head" changes, the
fundamental belief here is that iterating a linked list is much slower
than iterating an array (5-15x slower in my testing). There's also an
associated belief that since we iterate the batch of folios three times,
we do better when the array is small (ie 15 entries) than we do with a
batch that is hundreds of entries long, which only gives us the
opportunity for the first pages to fall out of cache by the time we get to
the end.
It is possible we should increase the size of folio_batch. Hopefully the
bots let us know if this introduces any performance regressions.
This patch (of 3):
By making release_pages() call folios_put(), we can get rid of the calls
to compound_head() for the callers that already know they have folios. We
can also get rid of the lock_batch tracking as we know the size of the
batch is limited by folio_batch. This does reduce the maximum number of
pages for which the lruvec lock is held, from SWAP_CLUSTER_MAX (32) to
PAGEVEC_SIZE (15). I do not expect this to make a significant difference,
but if it does, we can increase PAGEVEC_SIZE to 31.
Link: https://lkml.kernel.org/r/20240227174254.710559-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240227174254.710559-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm: remove total_mapcount()", v2.
Let's remove the remaining user from mm/memfd.c so we can get rid of
total_mapcount().
This patch (of 2):
Both functions are the remaining users of total_mapcount(). Let's get rid
of the calls by converting the code to folios.
As it turns out, the code is unnecessarily complicated, especially:
1) We can query the number of pagecache references for a folio simply via
folio_nr_pages(). This will handle other folio sizes in the future
correctly.
2) The xas_set(xas, page->index + cache_count) call to increment the
iterator for large folios is not required. Remove it.
Further, simplify the XA_CHECK_SCHED check, counting each entry exactly
once.
Memfd pages can be swapped out when using shmem; leave xa_is_value()
checks in place.
Link: https://lkml.kernel.org/r/20240226141324.278526-1-david@redhat.com
Link: https://lkml.kernel.org/r/20240226141324.278526-2-david@redhat.com
Co-developed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
While doing MADV_PAGEOUT, the current code will clear PTE young so that
vmscan won't read young flags to allow the reclamation of madvised folios
to go ahead. It seems we can do it by directly ignoring references, thus
we can remove tlb flush in madvise and rmap overhead in vmscan.
Regarding the side effect, in the original code, if a parallel thread runs
side by side to access the madvised memory with the thread doing madvise,
folios will get a chance to be re-activated by vmscan (though the time gap
is actually quite small since checking PTEs is done immediately after
clearing PTEs young). But with this patch, they will still be reclaimed.
But this behaviour doing PAGEOUT and doing access at the same time is
quite silly like DoS. So probably, we don't need to care. Or ignoring
the new access during the quite small time gap is even better.
For DAMON's DAMOS_PAGEOUT based on physical address region, we still keep
its behaviour as is since a physical address might be mapped by multiple
processes. MADV_PAGEOUT based on virtual address is actually much more
aggressive on reclamation. To untouch paddr's DAMOS_PAGEOUT, we simply
pass ignore_references as false in reclaim_pages().
A microbench as below has shown 6% decrement on the latency of
MADV_PAGEOUT,
#define PGSIZE 4096
main()
{
int i;
#define SIZE 512*1024*1024
volatile long *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
for (i = 0; i < SIZE/sizeof(long); i += PGSIZE / sizeof(long))
p[i] = 0x11;
madvise(p, SIZE, MADV_PAGEOUT);
}
w/o patch w/ patch
root@10:~# time ./a.out root@10:~# time ./a.out
real 0m49.634s real 0m46.334s
user 0m0.637s user 0m0.648s
sys 0m47.434s sys 0m44.265s
Link: https://lkml.kernel.org/r/20240226005739.24350-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The doc needs a fix. As only in the case of virtual address, we are
calling madvise() with MADV_PAGEOUT. But in the case of physical address,
we are calling reclaim_pages() directly. MADV_PAGEOUT on virtual address
is much more aggresive to reclaim memory compared to reclaim_pages() on
paddr region. This patch removes the details so that the description can
apply to both cases. And we don't need to couple with the implementation
details.
Link: https://lkml.kernel.org/r/20240224224751.4673-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The stack_pools[] array has DEPOT_MAX_POOLS. The "pools_num" tracks the
number of pools which are initialized. See depot_init_pool() for more
details.
If pool_index == pools_num_cached, this will read one element beyond what
we want. If not all the pools are initialized, then the pool will be
NULL, triggering a WARN(), and if they are all initialized it will read
one element beyond the end of the array.
Link: https://lkml.kernel.org/r/361ac881-60b7-471f-91e5-5bf8fe8042b2@moroto.mountain
Fixes: b29d318858 ("lib/stackdepot: store free stack records in a freelist")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The current implementation of the mark_victim tracepoint provides only the
process ID (pid) of the victim process. This limitation poses challenges
for userspace tools requiring real-time OOM analysis and intervention.
Although this information is available from the kernel logs, it’s not
the appropriate format to provide OOM notifications. In Android, BPF
programs are used with the mark_victim trace events to notify userspace of
an OOM kill. For consistency, update the trace event to include the same
information about the OOMed victim as the kernel logs.
- UID
In Android each installed application has a unique UID. Including
the `uid` assists in correlating OOM events with specific apps.
- Process Name (comm)
Enables identification of the affected process.
- OOM Score
Will allow userspace to get additional insight of the relative kill
priority of the OOM victim. In Android, the oom_score_adj is used to
categorize app state (foreground, background, etc.), which aids in
analyzing user-perceptible impacts of OOM events [1].
- Total VM, RSS Stats, and pgtables
Amount of memory used by the victim that will, potentially, be freed up
by killing it.
[1] https://cs.android.com/android/platform/superproject/main/+/246dc8fc95b6d93afcba5c6d6c133307abb3ac2e:frameworks/base/services/core/java/com/android/server/am/ProcessList.java;l=188-283
Signed-off-by: Carlos Galo <carlosgalo@google.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hugetlb can now safely handle faults under the VMA lock, so allow it to do
so.
This patch may cause ltp hugemmap10 to "fail". Hugemmap10 tests hugetlb
counters, and expects the counters to remain unchanged on failure to
handle a fault.
In hugetlb_no_page(), vmf_anon_prepare() may bailout with no anon_vma
under the VMA lock after allocating a folio for the hugepage. In
free_huge_folio(), this folio is completely freed on bailout iff there is
a surplus of hugetlb pages. This will remove a folio off the freelist and
decrement the number of hugepages while ltp expects these counters to
remain unchanged on failure.
Originally this could only happen due to OOM failures, but now it may also
occur after we allocate a hugetlb folio without a suitable anon_vma under
the VMA lock. This should only happen for the first freshly allocated
hugepage in this vma.
Link: https://lkml.kernel.org/r/20240221234732.187629-6-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
hugetlb_fault() currently defines a vm_fault to pass to the generic
handle_userfault() function. We can move this definition to the top of
hugetlb_fault() so that it can be used throughout the rest of the hugetlb
fault path.
This will help cleanup a number of excess variables and function arguments
throughout the stack. Also, since vm_fault already has space to store the
page offset, use that instead and get rid of idx.
Link: https://lkml.kernel.org/r/20240221234732.187629-3-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Handle hugetlb faults under the VMA lock", v2.
It is generally safe to handle hugetlb faults under the VMA lock. The
only time this is unsafe is when no anon_vma has been allocated to this
vma yet, so we can use vmf_anon_prepare() instead of anon_vma_prepare() to
bailout if necessary. This should only happen for the first hugetlb page
in the vma.
Additionally, this patchset begins to use struct vm_fault within
hugetlb_fault(). This works towards cleaning up hugetlb code, and should
significantly reduce the number of arguments passed to functions.
The last patch in this series may cause ltp hugemmap10 to "fail". This is
because vmf_anon_prepare() may bailout with no anon_vma under the VMA lock
after allocating a folio for the hugepage. In free_huge_folio(), this
folio is completely freed on bailout iff there is a surplus of hugetlb
pages. This will remove a folio off the freelist and decrement the number
of hugepages while ltp expects these counters to remain unchanged on
failure. The rest of the ltp testcases pass.
This patch (of 2):
In order to handle hugetlb faults under the VMA lock, hugetlb can use
vmf_anon_prepare() to ensure we can safely prepare an anon_vma. Change it
to be a non-static function so it can be used within hugetlb as well.
Link: https://lkml.kernel.org/r/20240221234732.187629-6-vishal.moola@gmail.com
Link: https://lkml.kernel.org/r/20240221234732.187629-2-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Matthew Wilcox (Oracle)
Lance Yang
Martin Kaiser
David Hildenbrand
Zi Yan
Suren Baghdasaryan
Barry Song
Ryan Roberts
Paul Heidekrüger
Dan Carpenter
Kefeng Wang
Carlos Galo
Javier Carrasco
Vincenzo Mezzela
Vishal Moola (Oracle)
Hao Ge
Yosry Ahmed