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From: Paolo Bonzini <pbonzini@redhat.com>
To: Nicholas Thomas <nick@bytemark.co.uk>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 12/12] nbd: split requests
Date: Fri, 09 Sep 2011 17:33:57 +0200	[thread overview]
Message-ID: <4E6A31E5.3070208@redhat.com> (raw)
In-Reply-To: <4E6A2823.9080103@bytemark.co.uk>

On 09/09/2011 04:52 PM, Nicholas Thomas wrote:
>> >  +/* qemu-nbd has a limit of slightly less than 1M per request.  For safety,
>> >  + * transfer at most 512K per request. */
>> >  +#define NBD_MAX_SECTORS 1024
>
> As far as I'm aware, the limit of 1MiB - header size is common to all
> NBD servers. I'm not aware of anything at all that'll fail on a 768K
> request but succeed in the exact same circumstances on a 512K request.
> Again, this is a performance consideration - each request is relatively
> slow, so you don't want them to be unnecessarily small.

Yes, it should probably be bumped to 1536 or 2040 (to keep requests 
4k-aligned).  I wasn't sure about the limit.  I've never seen requests 
that big anyway.

Paolo

  reply	other threads:[~2011-09-09 15:34 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-08 15:24 [Qemu-devel] [PATCH 00/12] nbd improvements Paolo Bonzini
2011-09-08 15:24 ` [Qemu-devel] [PATCH 01/12] nbd: support feature negotiation Paolo Bonzini
2011-09-08 15:24 ` [Qemu-devel] [PATCH 02/12] nbd: sync API definitions with upstream Paolo Bonzini
2011-09-12 14:15   ` Kevin Wolf
2011-09-12 15:08     ` Paolo Bonzini
2011-09-08 15:24 ` [Qemu-devel] [PATCH 03/12] nbd: support NBD_SET_FLAGS ioctl Paolo Bonzini
2011-09-08 15:24 ` [Qemu-devel] [PATCH 04/12] nbd: add support for NBD_CMD_FLUSH Paolo Bonzini
2011-09-13 13:52   ` Kevin Wolf
2011-09-13 15:13     ` Paolo Bonzini
2011-09-08 15:24 ` [Qemu-devel] [PATCH 05/12] nbd: add support for NBD_CMD_FLAG_FUA Paolo Bonzini
2011-09-13 13:55   ` Kevin Wolf
2011-09-08 15:24 ` [Qemu-devel] [PATCH 06/12] nbd: support NBD_CMD_TRIM in the server Paolo Bonzini
2011-09-13 13:58   ` Kevin Wolf
2011-09-13 15:14     ` Paolo Bonzini
2011-09-14 15:44   ` Christoph Hellwig
2011-09-14 16:25     ` Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 07/12] sheepdog: add coroutine_fn markers Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 08/12] add socket_set_block Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 09/12] sheepdog: move coroutine send/recv function to generic code Paolo Bonzini
2011-09-09  4:53   ` MORITA Kazutaka
2011-09-09  8:11     ` [Qemu-devel] [PATCH v2 " Paolo Bonzini
2011-09-13  0:28       ` MORITA Kazutaka
2011-09-13 14:14       ` Kevin Wolf
2011-09-13 15:16         ` Paolo Bonzini
2011-09-13 15:36           ` Kevin Wolf
2011-09-13 15:38             ` Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 10/12] block: add bdrv_co_flush support Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 11/12] nbd: switch to asynchronous operation Paolo Bonzini
2011-09-09 14:52   ` Nicholas Thomas
2011-09-09 15:03     ` Paolo Bonzini
2011-09-09 15:34       ` Paolo Bonzini
2011-09-08 15:25 ` [Qemu-devel] [PATCH 12/12] nbd: split requests Paolo Bonzini
2011-09-09 14:52   ` Nicholas Thomas
2011-09-09 15:33     ` Paolo Bonzini [this message]
2011-09-09  9:00 ` [Qemu-devel] [PATCH 00/12] nbd improvements Kevin Wolf
2011-09-09 10:29   ` Paolo Bonzini
2011-09-09 10:42     ` Kevin Wolf
2011-09-09 10:50     ` Nicholas Thomas
2011-09-09 11:00       ` Paolo Bonzini
2011-09-09 11:04       ` Kevin Wolf
2011-09-09 14:51         ` Nicholas Thomas
2011-09-14  9:50 ` Kevin Wolf

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