From: Anthony Liguori <anthony@codemonkey.ws>
To: qemu-devel@nongnu.org
Cc: Uri Lublin <uril@redhat.com>
Subject: Re: [Qemu-devel] migration: adding migration to/from a file (v2)
Date: Thu, 19 Feb 2009 14:06:41 -0600 [thread overview]
Message-ID: <499DBBD1.1020602@codemonkey.ws> (raw)
In-Reply-To: <20090219193733.GB22319@shareable.org>
Jamie Lokier wrote:
>
>> Remember, migration is a streaming
>> protocol, not a random access, so it only makes sense to have one
>> outstanding request at a time.
>>
>
> Fwow, often with streaming (in general) the highest performance comes
> from having two or more outstanding requests at a time, so there are
> no gaps between requests being processed at the OS and device level.
>
> However, unless migrate-to-file uses O_DIRECT that will be hidden by
> the OS's buffering.
>
It's already buffered FWIW by the savevm infrastructure. You'll won't
usually see small operations.
Regards,
Anthony Liguori
> Then the remaining overhead from AIOs (or fake AIOs using threads) is
> lots context switching, one per write completed.
>
> -- Jamie
>
>
>
next prev parent reply other threads:[~2009-02-19 20:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-19 11:45 [Qemu-devel] migration: adding migration to/from a file (v2) Uri Lublin
2009-02-19 13:57 ` Anthony Liguori
2009-02-19 16:14 ` Uri Lublin
2009-02-19 16:51 ` Anthony Liguori
2009-02-19 19:06 ` Uri Lublin
2009-02-19 20:05 ` Anthony Liguori
2009-02-19 20:28 ` Jamie Lokier
2009-02-19 23:36 ` M. Warner Losh
2009-02-19 23:59 ` Anthony Liguori
2009-02-20 0:36 ` M. Warner Losh
2009-02-19 20:45 ` Uri Lublin
2009-02-19 19:37 ` Jamie Lokier
2009-02-19 20:06 ` Anthony Liguori [this message]
2009-02-19 19:33 ` Jamie Lokier
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