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Commit0a4954a

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ftang1torvalds
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percpu_counter: add percpu_counter_sync()
percpu_counter's accuracy is related to its batch size. For apercpu_counter with a big batch, its deviation could be big, so when thecounter's batch is runtime changed to a smaller value for better accuracy,there could also be requirment to reduce the big deviation.So add a percpu-counter sync function to be run on each CPU.Reported-by: kernel test robot <rong.a.chen@intel.com>Signed-off-by: Feng Tang <feng.tang@intel.com>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>Cc: Dennis Zhou <dennis@kernel.org>Cc: Tejun Heo <tj@kernel.org>Cc: Christoph Lameter <cl@linux.com>Cc: Michal Hocko <mhocko@suse.com>Cc: Qian Cai <cai@lca.pw>Cc: Andi Kleen <andi.kleen@intel.com>Cc: Huang Ying <ying.huang@intel.com>Cc: Dave Hansen <dave.hansen@intel.com>Cc: Haiyang Zhang <haiyangz@microsoft.com>Cc: Johannes Weiner <hannes@cmpxchg.org>Cc: Kees Cook <keescook@chromium.org>Cc: "K. Y. Srinivasan" <kys@microsoft.com>Cc: Matthew Wilcox (Oracle) <willy@infradead.org>Cc: Mel Gorman <mgorman@suse.de>Cc: Tim Chen <tim.c.chen@intel.com>Link:http://lkml.kernel.org/r/1594389708-60781-4-git-send-email-feng.tang@intel.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent4e2ee51 commit0a4954a

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‎include/linux/percpu_counter.h‎

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@@ -44,6 +44,7 @@ void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
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s32batch);
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s64__percpu_counter_sum(structpercpu_counter*fbc);
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int__percpu_counter_compare(structpercpu_counter*fbc,s64rhs,s32batch);
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voidpercpu_counter_sync(structpercpu_counter*fbc);
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staticinlineintpercpu_counter_compare(structpercpu_counter*fbc,s64rhs)
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{
@@ -172,6 +173,9 @@ static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
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return true;
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}
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staticinlinevoidpercpu_counter_sync(structpercpu_counter*fbc)
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{
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}
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#endif/* CONFIG_SMP */
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staticinlinevoidpercpu_counter_inc(structpercpu_counter*fbc)

‎lib/percpu_counter.c‎

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@@ -98,6 +98,25 @@ void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
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}
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EXPORT_SYMBOL(percpu_counter_add_batch);
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/*
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* For percpu_counter with a big batch, the devication of its count could
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* be big, and there is requirement to reduce the deviation, like when the
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* counter's batch could be runtime decreased to get a better accuracy,
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* which can be achieved by running this sync function on each CPU.
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*/
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voidpercpu_counter_sync(structpercpu_counter*fbc)
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{
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unsigned longflags;
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s64count;
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raw_spin_lock_irqsave(&fbc->lock,flags);
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count=__this_cpu_read(*fbc->counters);
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fbc->count+=count;
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__this_cpu_sub(*fbc->counters,count);
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raw_spin_unlock_irqrestore(&fbc->lock,flags);
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}
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EXPORT_SYMBOL(percpu_counter_sync);
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/*
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* Add up all the per-cpu counts, return the result. This is a more accurate
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* but much slower version of percpu_counter_read_positive()

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