From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@kamp.de>, ronnie sahlberg <ronniesahlberg@gmail.com>
Cc: "Benoît Canet" <benoit.canet@irqsave.net>,
"Kevin Wolf" <kwolf@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Max Reitz" <mreitz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests
Date: Mon, 08 Sep 2014 17:27:36 +0200 [thread overview]
Message-ID: <540DCAE8.4060701@redhat.com> (raw)
In-Reply-To: <540DC8D7.80905@kamp.de>
Il 08/09/2014 17:18, Peter Lieven ha scritto:
>>
>> That's why we have splitting code for discard, and why we would have to
>> add it for read/write too.
>
> Why should a guest generate such big requests.
When copying data, gparted will try using very large I/O sizes. Of
course if something breaks it will just use a smaller size, but it would
make performance worse.
I tried now (with local storage, not virtual---but with such large block
sizes it's disk bound anyway, one request can take 0.1 seconds to
execute) and a 2 MB block size is 20% slower than 16 MB block size on
your usual 3.5" rotational SATA disk.
Paolo
> Afaik the reported
> limit for e.g. virtio-blk is 1024 sectors (reported through blockdev
> --getmaxsect /dev/vda).
> I think it was only the multiwrite_merge code causing trouble here.
next prev parent reply other threads:[~2014-09-08 15:28 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-05 16:51 [Qemu-devel] [PATCH 0/4] introduce max_transfer_length Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 1/4] BlockLimits: " Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests Peter Lieven
2014-09-08 13:44 ` Benoît Canet
2014-09-08 13:49 ` Paolo Bonzini
2014-09-08 13:56 ` Peter Lieven
2014-09-08 13:58 ` Paolo Bonzini
2014-09-08 14:35 ` Peter Lieven
2014-09-08 14:42 ` Paolo Bonzini
2014-09-08 14:54 ` Peter Lieven
2014-09-23 8:47 ` Kevin Wolf
2014-09-23 8:55 ` Peter Lieven
2014-09-23 9:09 ` Kevin Wolf
2014-09-08 15:13 ` ronnie sahlberg
2014-09-08 15:15 ` Paolo Bonzini
2014-09-08 15:18 ` Peter Lieven
2014-09-08 15:27 ` Paolo Bonzini [this message]
2014-09-08 16:18 ` Peter Lieven
2014-09-08 16:29 ` Paolo Bonzini
2014-09-12 11:43 ` Peter Lieven
2014-09-18 14:12 ` Paolo Bonzini
2014-09-18 14:16 ` Peter Lieven
2014-09-18 14:17 ` Paolo Bonzini
2014-09-18 22:57 ` Peter Lieven
2014-09-08 15:16 ` Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 3/4] block/iscsi: set max_transfer_length Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 4/4] block: avoid creating oversized writes in multiwrite_merge Peter Lieven
2014-09-18 14:13 ` Paolo Bonzini
2014-09-18 22:56 ` Peter Lieven
2014-09-19 13:33 ` Paolo Bonzini
2014-09-22 9:43 ` Peter Lieven
2014-09-22 19:06 ` Paolo Bonzini
2014-09-23 6:15 ` Peter Lieven
2014-09-23 8:59 ` Kevin Wolf
2014-09-23 9:04 ` Peter Lieven
2014-09-23 9:32 ` Peter Lieven
2014-09-23 9:47 ` Kevin Wolf
2014-09-23 9:52 ` Peter Lieven
2014-09-23 10:05 ` Kevin Wolf
2014-09-30 7:26 ` Peter Lieven
2014-09-30 8:03 ` Kevin Wolf
2014-09-05 17:05 ` [Qemu-devel] [PATCH 0/4] introduce max_transfer_length ronnie sahlberg
2014-09-05 19:52 ` Peter Lieven
2014-09-05 21:22 ` ronnie sahlberg
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