From: Roger Heflin <rogerheflin@gmail.com>
To: Coly Li <colyli@suse.de>
Cc: Linux RAID <linux-raid@vger.kernel.org>,
Guoqing Jiang <guoqing.jiang@cloud.ionos.com>,
Song Liu <songliubraving@fb.com>, xiao ni <xni@redhat.com>
Subject: Re: unexpected 'mdadm -S' hang with I/O pressure testing
Date: Sun, 13 Sep 2020 19:03:24 -0500 [thread overview]
Message-ID: <CAAMCDed81-NbMaqcBG3UV=7X7yp7jQ=rX9vs50_6jviTbiDk0Q@mail.gmail.com> (raw)
In-Reply-To: <a5f14765-4da8-e965-beed-3d01ac496c61@suse.de>
You might want to see how high Dirty is in /proc/meminfo. That is how
much write io has to finish if fio runs a sync call, and it would also
apply to the stop since it should also call a sync.
On most oses the default is some percentage of your total ram and can
be quite high especially if the io rates are low. ie if you had 1gb
of data and your write rate was 1MB/sec (random IO) then 1000 seconds.
If you test and this is the issue you should be able to from another
window watch dirty slowed go down.
I set mine low as I don't ever want there to be a significant amount
of writes outstanding. I use these values (5MB and 3MB).
vm.dirty_background_bytes = 3000000
vm.dirty_background_ratio = 0
vm.dirty_bytes = 5000000
vm.dirty_ratio = 0
prev parent reply other threads:[~2020-09-14 0:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-12 14:06 unexpected 'mdadm -S' hang with I/O pressure testing Coly Li
2020-09-12 14:21 ` Coly Li
2020-09-12 14:59 ` Xiao Ni
2020-09-14 0:03 ` Roger Heflin [this message]
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