Messages in this thread | | | Subject | Re: [PATCH] bcache: add cond_resched() in __bch_cache_cmp() | From | Shile Zhang <> | Date | Thu, 7 Mar 2019 23:06:47 +0800 |
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On 2019/3/7 18:34, Coly Li wrote: > On 2019/3/7 1:15 下午, shile.zhang@linux.alibaba.com wrote: >> From: Shile Zhang <shile.zhang@linux.alibaba.com> >> >> Read /sys/fs/bcache/<uuid>/cacheN/priority_stats can take very long >> time with huge cache after long run. >> >> Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> > Hi Shile, > > Do you test your change ? It will be helpful with more performance data > (what problem that you improved).
In case of 960GB SSD cache device, once read of the 'priority_stats' costs about 600ms in our test environment.
The perf tool shown that near 50% CPU time consumed by 'sort()', this means once sort will hold the CPU near 300ms.
In our case, the statistics collector reads the 'priority_stats' periodically, it will trigger the schedule latency jitters of the
task which shared same CPU core.
> > Thanks. > > Coly Li > >> --- >> drivers/md/bcache/sysfs.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c >> index 557a8a3..028fea1 100644 >> --- a/drivers/md/bcache/sysfs.c >> +++ b/drivers/md/bcache/sysfs.c >> @@ -897,6 +897,7 @@ static void bch_cache_set_internal_release(struct kobject *k) >> >> static int __bch_cache_cmp(const void *l, const void *r) >> { >> + cond_resched(); >> return *((uint16_t *)r) - *((uint16_t *)l); >> } >> >> >
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