Messages in this thread | | | Subject | Re: [PATCH] bcache: add cond_resched() in __bch_cache_cmp() | From | Coly Li <> | Date | Thu, 7 Mar 2019 23:36:18 +0800 |
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On 2019/3/7 11:06 下午, Shile Zhang wrote: > > 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. >
After the fix, how much time it takes ?
> 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. >
Hmm, it seems you just make the sort slower, and nothing more changes. Am I right ?
Coly Li
>> >> 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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Coly Li
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