From: Omar Sandoval <osandov@osandov.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, kernel-team@fb.com, stable@vger.kernel.org
Subject: Re: [PATCH] block: use nanosecond resolution for iostat
Date: Mon, 24 Sep 2018 10:31:48 -0700 [thread overview]
Message-ID: <20180924173148.GA24295@vader> (raw)
In-Reply-To: <6e054549-7ffa-2c97-7cad-814cbb962444@kernel.dk>
On Fri, Sep 21, 2018 at 08:27:17PM -0600, Jens Axboe wrote:
> On 9/21/18 5:44 PM, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> >
> > Klaus Kusche reported that the I/O busy time in /proc/diskstats was not
> > updating properly on 4.18. This is because we started using ktime to
> > track elapsed time, and we convert nanoseconds to jiffies when we update
> > the partition counter. However, this gets rounded down, so any I/Os that
> > take less than a jiffy are not accounted for. Previously in this case,
> > the value of jiffies would sometimes increment while we were doing I/O,
> > so at least some I/Os were accounted for.
> >
> > Let's convert the stats to use nanoseconds internally. We still report
> > milliseconds as before, now more accurately than ever. The value is
> > still truncated to 32 bits for backwards compatibility.
>
> Thanks Omar, applied for 4.19.
Thanks, Jens. I also just pushed a regression test to blktests.
prev parent reply other threads:[~2018-09-24 23:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 23:44 [PATCH] block: use nanosecond resolution for iostat Omar Sandoval
2018-09-22 2:27 ` Jens Axboe
2018-09-24 17:31 ` Omar Sandoval [this message]
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