diff options
Diffstat (limited to '0015-ZEN-mm-Stop-kswapd-early-when-nothing-s-waiting-for-.patch')
| -rw-r--r-- | 0015-ZEN-mm-Stop-kswapd-early-when-nothing-s-waiting-for-.patch | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/0015-ZEN-mm-Stop-kswapd-early-when-nothing-s-waiting-for-.patch b/0015-ZEN-mm-Stop-kswapd-early-when-nothing-s-waiting-for-.patch new file mode 100644 index 000000000000..fedcdd3f6a29 --- /dev/null +++ b/0015-ZEN-mm-Stop-kswapd-early-when-nothing-s-waiting-for-.patch @@ -0,0 +1,108 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Sultan Alsawaf <sultan@kerneltoast.com> +Date: Sun, 19 Apr 2020 19:59:18 -0700 +Subject: [PATCH] ZEN: mm: Stop kswapd early when nothing's waiting for it to + free pages + +Contains: + - mm: Stop kswapd early when nothing's waiting for it to free pages + + Keeping kswapd running when all the failed allocations that invoked it + are satisfied incurs a high overhead due to unnecessary page eviction + and writeback, as well as spurious VM pressure events to various + registered shrinkers. When kswapd doesn't need to work to make an + allocation succeed anymore, stop it prematurely to save resources. + + Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> + + - mm: Don't stop kswapd on a per-node basis when there are no waiters + + The page allocator wakes all kswapds in an allocation context's allowed + nodemask in the slow path, so it doesn't make sense to have the kswapd- + waiter count per each NUMA node. Instead, it should be a global counter + to stop all kswapds when there are no failed allocation requests. + + Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> +--- + mm/internal.h | 1 + + mm/page_alloc.c | 17 ++++++++++++++--- + mm/vmscan.c | 3 ++- + 3 files changed, 17 insertions(+), 4 deletions(-) + +diff --git a/mm/internal.h b/mm/internal.h +index c0f8fbe0445b5f1704c41e2a4f2b664456b9768f..cd447101241b1e7245c84cf25c2fba4d56c1df72 100644 +--- a/mm/internal.h ++++ b/mm/internal.h +@@ -361,6 +361,7 @@ extern void prep_compound_page(struct page *page, unsigned int order); + extern void post_alloc_hook(struct page *page, unsigned int order, + gfp_t gfp_flags); + extern int user_min_free_kbytes; ++extern atomic_long_t kswapd_waiters; + + extern void free_unref_page(struct page *page, unsigned int order); + extern void free_unref_page_list(struct list_head *list); +diff --git a/mm/page_alloc.c b/mm/page_alloc.c +index d6fc4723c4e9137a3bf8193fcbad1bb23f041c43..d86f3da635751e00a5ca5f9c386415523d2ff40a 100644 +--- a/mm/page_alloc.c ++++ b/mm/page_alloc.c +@@ -122,6 +122,8 @@ typedef int __bitwise fpi_t; + */ + #define FPI_SKIP_KASAN_POISON ((__force fpi_t)BIT(2)) + ++atomic_long_t kswapd_waiters = ATOMIC_LONG_INIT(0); ++ + /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */ + static DEFINE_MUTEX(pcp_batch_high_lock); + #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8) +@@ -4921,6 +4923,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, + int no_progress_loops; + unsigned int cpuset_mems_cookie; + int reserve_flags; ++ bool woke_kswapd = false; + + /* + * We also sanity check to catch abuse of atomic reserves being used by +@@ -4967,8 +4970,13 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, + goto nopage; + } + +- if (alloc_flags & ALLOC_KSWAPD) ++ if (alloc_flags & ALLOC_KSWAPD) { ++ if (!woke_kswapd) { ++ atomic_long_inc(&kswapd_waiters); ++ woke_kswapd = true; ++ } + wake_all_kswapds(order, gfp_mask, ac); ++ } + + /* + * The adjusted alloc_flags might result in immediate success, so try +@@ -5173,9 +5181,12 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, + goto retry; + } + fail: +- warn_alloc(gfp_mask, ac->nodemask, +- "page allocation failure: order:%u", order); + got_pg: ++ if (woke_kswapd) ++ atomic_long_dec(&kswapd_waiters); ++ if (!page) ++ warn_alloc(gfp_mask, ac->nodemask, ++ "page allocation failure: order:%u", order); + return page; + } + +diff --git a/mm/vmscan.c b/mm/vmscan.c +index f7d9a683e3a7d38fe1ffd0265b9f7d7acad938b4..c1936a256ed1e858febfe8f090f889f4a6238ff0 100644 +--- a/mm/vmscan.c ++++ b/mm/vmscan.c +@@ -4228,7 +4228,8 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx) + __fs_reclaim_release(_THIS_IP_); + ret = try_to_freeze(); + __fs_reclaim_acquire(_THIS_IP_); +- if (ret || kthread_should_stop()) ++ if (ret || kthread_should_stop() || ++ !atomic_long_read(&kswapd_waiters)) + break; + + /* |