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| author | Feng Tang <feng.tang@intel.com> | 2020-08-06 23:23:11 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-07 11:33:26 -0700 |
| commit | 0a4954a850b0c4d0a5d18b1a55d6e5a653e362b5 (patch) | |
| tree | 28dc147820ec43d7c15f4e8c51e024b8eebd02c0 | |
| parent | 4e2ee51e82510813969eff9feff8e570a8a28c73 (diff) | |
| download | lwn-0a4954a850b0c4d0a5d18b1a55d6e5a653e362b5.tar.gz lwn-0a4954a850b0c4d0a5d18b1a55d6e5a653e362b5.zip | |
percpu_counter: add percpu_counter_sync()
percpu_counter's accuracy is related to its batch size. For a
percpu_counter with a big batch, its deviation could be big, so when the
counter'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.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/percpu_counter.h | 4 | ||||
| -rw-r--r-- | lib/percpu_counter.c | 19 |
2 files changed, 23 insertions, 0 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 0a4f54dd4737..01861eebed79 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -44,6 +44,7 @@ void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch); s64 __percpu_counter_sum(struct percpu_counter *fbc); int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch); +void percpu_counter_sync(struct percpu_counter *fbc); static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs) { @@ -172,6 +173,9 @@ static inline bool percpu_counter_initialized(struct percpu_counter *fbc) return true; } +static inline void percpu_counter_sync(struct percpu_counter *fbc) +{ +} #endif /* CONFIG_SMP */ static inline void percpu_counter_inc(struct percpu_counter *fbc) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index a66595ba5543..a2345de90e93 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -99,6 +99,25 @@ void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch) EXPORT_SYMBOL(percpu_counter_add_batch); /* + * For percpu_counter with a big batch, the devication of its count could + * be big, and there is requirement to reduce the deviation, like when the + * counter's batch could be runtime decreased to get a better accuracy, + * which can be achieved by running this sync function on each CPU. + */ +void percpu_counter_sync(struct percpu_counter *fbc) +{ + unsigned long flags; + s64 count; + + raw_spin_lock_irqsave(&fbc->lock, flags); + count = __this_cpu_read(*fbc->counters); + fbc->count += count; + __this_cpu_sub(*fbc->counters, count); + raw_spin_unlock_irqrestore(&fbc->lock, flags); +} +EXPORT_SYMBOL(percpu_counter_sync); + +/* * Add up all the per-cpu counts, return the result. This is a more accurate * but much slower version of percpu_counter_read_positive() */ |