From: Alexandre DERUMIER <aderumier@odiso.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [Qemu-block] [PATCH 1/3] blockjob: Introduce block_job_relax_cpu
Date: Fri, 10 Jul 2015 05:42:48 +0200 (CEST) [thread overview]
Message-ID: <1233193551.9344767.1436499768115.JavaMail.zimbra@oxygem.tv> (raw)
In-Reply-To: <20150709125455.GA11166@stefanha-thinkpad.redhat.com>
Hi Stefan,
>>By the way, why did you choose 10 milliseconds? That is quite long.
>>
>>If this function is called once per 10 ms disk I/O operations then we
>>lose 50% utilization. 1 ms or less would be reasonable.
>From my tests, 1ms is not enough, It still hanging in guest or qmp queries.
10ms give me optimal balance between bitmap scan speed and guest responsiveness.
I don't known if this can be compute automaticaly ? (maybe it's depend of disk lseek speed and cpu speed).
----- Mail original -----
De: "Stefan Hajnoczi" <stefanha@gmail.com>
À: "Fam Zheng" <famz@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>, "qemu-devel" <qemu-devel@nongnu.org>, qemu-block@nongnu.org
Envoyé: Jeudi 9 Juillet 2015 14:54:55
Objet: Re: [Qemu-devel] [Qemu-block] [PATCH 1/3] blockjob: Introduce block_job_relax_cpu
On Thu, Jul 09, 2015 at 11:47:56AM +0800, Fam Zheng wrote:
> block_job_sleep_ns is called by block job coroutines to yield the
> execution to VCPU threads and monitor etc. It is pointless to sleep for
> 0 or a few nanoseconds, because that equals to a "yield + enter" with no
> intermission in between (the timer fires immediately in the same
> iteration of event loop), which means other code still doesn't get a
> fair share of main loop / BQL.
>
> Introduce block_job_relax_cpu which will at least for
> BLOCK_JOB_RELAX_CPU_NS. Existing block_job_sleep_ns(job, 0) callers can
> be replaced by this later.
>
> Reported-by: Alexandre DERUMIER <aderumier@odiso.com>
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
> include/block/blockjob.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/include/block/blockjob.h b/include/block/blockjob.h
> index 57d8ef1..53ac4f4 100644
> --- a/include/block/blockjob.h
> +++ b/include/block/blockjob.h
> @@ -157,6 +157,22 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
> */
> void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns);
>
> +#define BLOCK_JOB_RELAX_CPU_NS 10000000L
By the way, why did you choose 10 milliseconds? That is quite long.
If this function is called once per 10 ms disk I/O operations then we
lose 50% utilization. 1 ms or less would be reasonable.
> +
> +/**
> + * block_job_relax_cpu:
> + * @job: The job that calls the function.
> + *
> + * Sleep a little to avoid intensive cpu time occupation. Block jobs should
> + * call this or block_job_sleep_ns (for more precision, but note that 0 ns is
> + * usually not enought) periodically, otherwise the QMP and VCPU could starve
s/enought/enough/
> + * on CPU and/or BQL.
> + */
> +static inline void block_job_relax_cpu(BlockJob *job)
coroutine_fn is missing.
next prev parent reply other threads:[~2015-07-10 3:42 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-09 3:47 [Qemu-devel] [PATCH 0/3] mirror: Fix guest responsiveness during bitmap scan Fam Zheng
2015-07-09 3:47 ` [Qemu-devel] [PATCH 1/3] blockjob: Introduce block_job_relax_cpu Fam Zheng
2015-07-09 12:54 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2015-07-10 3:42 ` Alexandre DERUMIER [this message]
2015-07-14 12:31 ` Stefan Hajnoczi
2015-07-15 10:32 ` Fam Zheng
2015-07-16 13:21 ` Stefan Hajnoczi
2015-07-09 3:47 ` [Qemu-devel] [PATCH 2/3] mirror: Use block_job_relax_cpu during bitmap scanning Fam Zheng
2015-07-09 13:00 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2015-07-09 3:47 ` [Qemu-devel] [PATCH 3/3] mirror: Speed up bitmap initial scanning Fam Zheng
2015-07-09 13:00 ` Stefan Hajnoczi
2015-07-14 13:21 ` Stefan Hajnoczi
2015-07-09 11:51 ` [Qemu-devel] [PATCH 0/3] mirror: Fix guest responsiveness during bitmap scan Alexandre DERUMIER
2015-07-09 13:02 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2015-07-09 13:18 ` Alexandre DERUMIER
2015-07-10 6:43 ` Fam Zheng
2015-07-10 6:54 ` Alexandre DERUMIER
2015-07-10 7:13 ` Fam Zheng
2015-07-10 10:36 ` Alexandre DERUMIER
2015-07-10 12:16 ` Alexandre DERUMIER
2015-07-13 5:08 ` Fam Zheng
2015-07-14 12:40 ` Stefan Hajnoczi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1233193551.9344767.1436499768115.JavaMail.zimbra@oxygem.tv \
--to=aderumier@odiso.com \
--cc=famz@redhat.com \
--cc=kwolf@redhat.com \
--cc=qemu-block@nongnu.org \
--cc=qemu-devel@nongnu.org \
--cc=stefanha@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.