From: Junichi Nomura <j-nomura@ce.jp.nec.com>
To: device-mapper development <dm-devel@redhat.com>
Subject: Re: ios and sectors should be incremented on completion
Date: Wed, 1 Oct 2014 08:26:05 +0000 [thread overview]
Message-ID: <542BBA9C.7010808@ce.jp.nec.com> (raw)
In-Reply-To: <20140926181236.177920a7a88d25a2d7189093@valinux.co.jp>
On 09/26/14 18:12, Akira Hayakawa wrote:
> I seems DM increments stats (ios and sectors) before completion.
> Why don't you do this in dec_pending?
> block/stat.txt says these values are incremented when I/O request completes.
>
> Is this to be fixed or do you have some justifications for this behavior?
Do you have a problem with the current behavior other than the document?
AFAIR, dm increments ios/sectors at submission because md did.
And other bio-based drivers such as drbd and nvme seem to have followed
the precedence.
While md has a reason to do so (some md personalities just remaps bios
and doesn't track completion), dm should be able to collect stat
in dec_pending as it always clones.
So, I think it's ok to move ios/sectors counting to end_io_acct().
It might make tools like iostat happier.
You might want to fix other bio-based drivers as well.
--
Jun'ichi Nomura, NEC Corporation
next prev parent reply other threads:[~2014-10-01 8:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-26 9:12 ios and sectors should be incremented on completion Akira Hayakawa
2014-10-01 8:26 ` Junichi Nomura [this message]
2014-10-22 1:55 ` Akira Hayakawa
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