From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@kamp.de>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com
Subject: Re: [Qemu-devel] [PATCH 1.8 5/6] qemu-img: add option to align writes to cluster_sectors during convert
Date: Mon, 25 Nov 2013 16:50:39 +0100 [thread overview]
Message-ID: <529371CF.3030507@redhat.com> (raw)
In-Reply-To: <52936D8C.50709@kamp.de>
Il 25/11/2013 16:32, Peter Lieven ha scritto:
>>
>> Also, a couple of ideas for separate patches. Perhaps the default value
>> of "-S" could be cluster_size if specified? This would avoid making raw
>> images too fragmented, and compounding filesystem-level fragmentation
>> with qcow2-level fragmentation. And 4K is too small a default in my
>> opinion; it could be easily changed to 64K, though 4K was of course an
>> improvement compared to 512 before commit a22f123 (qemu-img: Require
>> larger zero areas for sparse handling, 2011-08-26).
> I would vote for 64K or 256K, we already use the first for some time.
> However, it turned out
> that (much) bigger values decrease performance. Setting it
> to cluster_size can be dangerous. As described in my case its 15MB and
> I think for vhd its 1MB. This can be a lot of zeros that have to be
> written.
What about max(4096, min(bdi->cluster_size, 1048576))?
Paolo
next prev parent reply other threads:[~2013-11-25 15:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-25 13:57 [Qemu-devel] [PATCH 1.8 0/6] qemu-img convert optimizations Peter Lieven
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 1/6] qemu-img: add support for skipping zeroes in input during convert Peter Lieven
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 2/6] qemu-img: fix usage instruction for qemu-img convert Peter Lieven
2013-11-25 17:21 ` Eric Blake
2013-11-26 7:01 ` Peter Lieven
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 3/6] qemu-img: add option to specify alternate iobuffer size Peter Lieven
2013-11-25 14:54 ` Paolo Bonzini
2013-11-25 15:01 ` Peter Lieven
2013-11-25 15:07 ` Peter Lieven
2013-11-25 15:14 ` Paolo Bonzini
2013-11-25 15:24 ` Peter Lieven
2013-11-25 15:48 ` Paolo Bonzini
2013-11-25 15:56 ` Peter Lieven
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 4/6] block/iscsi: set bdi->cluster_size Peter Lieven
2013-11-25 14:51 ` Paolo Bonzini
2013-11-25 15:02 ` Paolo Bonzini
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 5/6] qemu-img: add option to align writes to cluster_sectors during convert Peter Lieven
2013-11-25 15:11 ` Paolo Bonzini
2013-11-25 15:32 ` Peter Lieven
2013-11-25 15:50 ` Paolo Bonzini [this message]
2013-11-25 15:55 ` Peter Lieven
2013-11-25 16:02 ` Paolo Bonzini
2013-11-25 16:11 ` Peter Lieven
2013-11-25 16:34 ` Paolo Bonzini
2013-11-25 13:57 ` [Qemu-devel] [PATCH 1.8 6/6] qemu-img: add option to show progress in sectors Peter Lieven
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