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From: Yehuda Sadeh Weinraub <yehudasa@gmail.com>
To: Christian Brunner <chb@muc.de>
Cc: ceph-devel@vger.kernel.org
Subject: Re: [PATCH] rbd: add queuing delay
Date: Mon, 21 Jun 2010 16:52:35 -0700	[thread overview]
Message-ID: <AANLkTikMSExF8V783S_wOsfCK7mRQT24g5SV4qaYUlrv@mail.gmail.com> (raw)
In-Reply-To: <20100620204426.GA7139@chb-desktop>

On Sun, Jun 20, 2010 at 1:44 PM, Christian Brunner <chb@muc.de> wrote:
> Hi Yehuda,
>
> while running tests with qemu-io I've been experiencing a lot of
> messages when running a large writev request (several hundred MB in
> a single call):
>
> 10.06.20 22:10:07.337108 b67dcb70 client4136.objecter  pg 3.437e on [0] is laggy: 33
> 10.06.20 22:10:07.337708 b67dcb70 client4136.objecter  pg 3.2553 on [0] is laggy: 19
> [...]
>
> Everything is working fine, though. I think that the large number of
> queued requests is the cause for this behaviour and I would propose to
> delay futher requests (see attached patch).
>
> What do you think about it?

It seems that the osd is lagging behind. The usleep might work for you
as you avoid the pressure, but it's also somewhat random and will
probably hurt performance on other setups. I'd rather see a
configurable solution that lets you specify a total in-flight bytes or
some other resizable window scheme.

>
> Another question: I there a way to figure out max_osd through librados?

Not currently.

Thanks,
Yehuda
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  reply	other threads:[~2010-06-21 23:52 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-20 20:44 [PATCH] rbd: add queuing delay Christian Brunner
2010-06-21 23:52 ` Yehuda Sadeh Weinraub [this message]
2010-06-22 20:27   ` Christian Brunner
2010-06-22 21:03     ` Yehuda Sadeh Weinraub
2010-06-27 21:05       ` Christian Brunner

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