From: Paul Brook <paul@codesourcery.com>
To: Ryan Harper <ryanh@us.ibm.com>
Cc: qemu-devel@nongnu.org, Anthony Liguori <aliguori@us.ibm.com>,
aliguori@linux.ibm.com, kvm@vger.kernel.org,
Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 4/4] Reallocate dma buffers in read/write path if needed
Date: Sun, 5 Oct 2008 00:00:27 +0100 [thread overview]
Message-ID: <200810050000.28154.paul@codesourcery.com> (raw)
In-Reply-To: <20081004214700.GH31395@us.ibm.com>
On Saturday 04 October 2008, Ryan Harper wrote:
> In all, it seems silly to worry about this sort of thing since the
> entire process could be contained with process ulimits if this is really
> a concern. Are we any more concerned that by splitting the requests
> into many smaller requests that we're wasting cpu, pegging the
> processor to 100% in some cases?
Using small requests may be a bit inefficient, but it still works and allows
the guest to make progress.
Allocating very large quantities of memory is very likely to kill the VM one
way or another. This is not acceptable, especially when the guest hasn't even
done anything wrong. There are legitimate circumstances where the size of the
outstanding IO requests may be comparable to the guest ram size.
Paul
next prev parent reply other threads:[~2008-10-04 23:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-03 22:05 [Qemu-devel] [PATCH 0/4] Improve emulated scsi write performance Ryan Harper
2008-10-03 22:05 ` [Qemu-devel] [PATCH 1/4] lsi_queue_command: add dma direction parameter Ryan Harper
2008-10-03 22:05 ` [Qemu-devel] [PATCH 2/4] Refactor lsi_do_command to queue read and write ops Ryan Harper
2008-10-03 22:05 ` [Qemu-devel] [PATCH 3/4] Refactor scsi-disk layer for queue'ing writes Ryan Harper
2008-10-03 22:05 ` [Qemu-devel] [PATCH 4/4] Reallocate dma buffers in read/write path if needed Ryan Harper
2008-10-03 23:17 ` Paul Brook
2008-10-03 23:35 ` Anthony Liguori
2008-10-04 0:00 ` Paul Brook
2008-10-04 10:00 ` Avi Kivity
[not found] ` <20081004135749.pphehrhuw9w4gwsc@imap.linux.ibm.com>
2008-10-04 21:47 ` Ryan Harper
2008-10-04 22:22 ` Anthony Liguori
2008-10-05 5:23 ` Avi Kivity
2008-10-05 23:06 ` Ryan Harper
2008-10-06 7:27 ` Avi Kivity
2008-10-04 23:00 ` Paul Brook [this message]
2008-10-05 5:29 ` Avi Kivity
2008-10-05 23:08 ` [Qemu-devel] [PATCH 0/4] Improve emulated scsi write performance Ryan Harper
2008-10-13 16:15 ` Ryan Harper
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