The patch titled
writeback: avoid unnecessary determine_dirtyable_memory call
has been added to the -mm tree. Its filename is
writeback-avoid-unnecessary-determine_dirtyable_memory-call.patch
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------------------------------------------------------
Subject: writeback: avoid unnecessary determine_dirtyable_memory call
From: Minchan Kim <minchan.kim@xxxxxxxxx>
I think determine_dirtyable_memory() is a rather costly function since it
need many atomic reads for gathering zone/global page state. But when we
use vm_dirty_bytes && dirty_background_bytes, we don't need that costly
calculation.
This patch eliminates such unnecessary overhead.
NOTE : newly added if condition might add overhead in normal path.
But it should be _really_ small because anyway we need the
access both vm_dirty_bytes and dirty_background_bytes so it is
likely to hit the cache.
Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff -puN mm/page-writeback.c~writeback-avoid-unnecessary-determine_dirtyable_memory-call mm/page-writeback.c
--- a/mm/page-writeback.c~writeback-avoid-unnecessary-determine_dirtyable_memory-call
+++ a/mm/page-writeback.c
@@ -390,9 +390,12 @@ void global_dirty_limits(unsigned long *
{
unsigned long background;
unsigned long dirty;
- unsigned long available_memory = determine_dirtyable_memory();
+ unsigned long available_memory;
struct task_struct *tsk;
+ if (!vm_dirty_bytes || !dirty_background_bytes)
+ available_memory = determine_dirtyable_memory();
+
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
else
_
Patches currently in -mm which might be from minchan.kim@xxxxxxxxx are
linux-next.patch
mm-vmap-area-cache.patch
mm-find_get_pages_contig-fixlet.patch
mm-deactivate-invalidated-pages.patch
mm-deactivate-invalidated-pages-fix.patch
vmalloc-remove-redundant-unlikely.patch
mm-kswapd-stop-high-order-balancing-when-any-suitable-zone-is-balanced.patch
mm-kswapd-keep-kswapd-awake-for-high-order-allocations-until-a-percentage-of-the-node-is-balanced.patch
mm-kswapd-use-the-order-that-kswapd-was-reclaiming-at-for-sleeping_prematurely.patch
mm-kswapd-reset-kswapd_max_order-and-classzone_idx-after-reading.patch
mm-kswapd-treat-zone-all_unreclaimable-in-sleeping_prematurely-similar-to-balance_pgdat.patch
mm-kswapd-use-the-classzone-idx-that-kswapd-was-using-for-sleeping_prematurely.patch
writeback-avoid-unnecessary-determine_dirtyable_memory-call.patch
writeback-avoid-unnecessary-determine_dirtyable_memory-call-fix.patch
mm-migration-use-rcu_dereference_protected-when-dereferencing-the-radix-tree-slot-during-file-page-migration.patch
mm-hugetlbc-fix-error-path-memory-leak-in-nr_hugepages_store_common.patch
mm-hugetlbc-fix-error-path-memory-leak-in-nr_hugepages_store_common-fix.patch
memcg-add-page_cgroup-flags-for-dirty-page-tracking.patch
memcg-document-cgroup-dirty-memory-interfaces.patch
memcg-document-cgroup-dirty-memory-interfaces-fix.patch
memcg-create-extensible-page-stat-update-routines.patch
memcg-add-lock-to-synchronize-page-accounting-and-migration.patch
memcg-remove-unnecessary-return-from-void-returning-mem_cgroup_del_lru_list.patch
memcg-use-zalloc-rather-than-mallocmemset.patch
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