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| author | Arun KS <arunks@codeaurora.org> | 2018-12-28 11:34:20 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-28 23:11:47 +0300 |
| commit | 3d6357de8aa09e1966770dc1171c72679946464f (patch) | |
| tree | a24bb2f8795ea4927c1ff64d5f5f00398bee925d /kernel/fork.c | |
| parent | fecd4a50baaebf6bde7f9e0b88fef13ffe5d98a1 (diff) | |
| download | linux-3d6357de8aa09e1966770dc1171c72679946464f.tar.xz | |
mm: reference totalram_pages and managed_pages once per function
Patch series "mm: convert totalram_pages, totalhigh_pages and managed
pages to atomic", v5.
This series converts totalram_pages, totalhigh_pages and
zone->managed_pages to atomic variables.
totalram_pages, zone->managed_pages and totalhigh_pages updates are
protected by managed_page_count_lock, but readers never care about it.
Convert these variables to atomic to avoid readers potentially seeing a
store tear.
Main motivation was that managed_page_count_lock handling was complicating
things. It was discussed in length here,
https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better
to remove the lock and convert variables to atomic. With the change,
preventing poteintial store-to-read tearing comes as a bonus.
This patch (of 4):
This is in preparation to a later patch which converts totalram_pages and
zone->managed_pages to atomic variables. Please note that re-reading the
value might lead to a different value and as such it could lead to
unexpected behavior. There are no known bugs as a result of the current
code but it is better to prevent from them in principle.
Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org
Signed-off-by: Arun KS <arunks@codeaurora.org>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index e2a5156bc9c3..8617a326e9f5 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -744,15 +744,16 @@ void __init __weak arch_task_cache_init(void) { } static void set_max_threads(unsigned int max_threads_suggested) { u64 threads; + unsigned long nr_pages = totalram_pages; /* * The number of threads shall be limited such that the thread * structures may only consume a small part of the available memory. */ - if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) + if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64) threads = MAX_THREADS; else - threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, + threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE, (u64) THREAD_SIZE * 8UL); if (threads > max_threads_suggested) |