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@xxxxxxxxxxxxxxxxx wrote:
>>> From: Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxxxxxxxxx>
>> 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);
>>> }
>>>
>>
--
Coly Li
