From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shile Zhang Subject: Re: [PATCH] bcache: add cond_resched() in __bch_cache_cmp() Date: Thu, 7 Mar 2019 23:06:47 +0800 Message-ID: <3640cd7f-f32a-1509-dbef-6000b6e14e75@linux.alibaba.com> References: <1551935728-243664-1-git-send-email-shile.zhang@linux.alibaba.com> <24916a71-39ff-7324-ad12-9d79cc68d0da@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <24916a71-39ff-7324-ad12-9d79cc68d0da@suse.de> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Coly Li Cc: Kent Overstreet , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-bcache@vger.kernel.org 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 >> >> Read /sys/fs/bcache//cacheN/priority_stats can take very long >> time with huge cache after long run. >> >> Signed-off-by: Shile Zhang > 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); >> } >> >> >