From: Avi Kivity <avi@redhat.com>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Anthony Liguori <aliguori@us.ibm.com>,
Ryan Harper <ryanh@us.ibm.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH 4/4] Reallocate dma buffers in read/write path if needed
Date: Sun, 05 Oct 2008 07:23:09 +0200 [thread overview]
Message-ID: <48E84F3D.4070301@redhat.com> (raw)
In-Reply-To: <48E7ECC1.90008@codemonkey.ws>
Anthony Liguori wrote:
>
> The second concern is that if a guest can allocate arbitrary amounts
> of memory, it could generate a swap storm. Unfortunately, AFAIK,
> Linux is not yet to a point where it can deal with swap fairness.
> Hopefully this is a limitation that the IO controller folks are taking
> into account.
Even if Linux was 100% fair (or rather 100% controlled -- we don't want
fairness here) in dealing with memory overcommit, we don't want swapping
just because a guest issued large requests. Breaking up large requests
will reduce efficiency (I believe negligibly is the limit is 1MB or
above), swapping will be much worse.
And again, there's no real reason to allocate memory here, we should be
doing I/O directly to the guest's scatter/gather buffers.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2008-10-05 5:30 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 [this message]
2008-10-05 23:06 ` Ryan Harper
2008-10-06 7:27 ` Avi Kivity
2008-10-04 23:00 ` Paul Brook
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=48E84F3D.4070301@redhat.com \
--to=avi@redhat.com \
--cc=aliguori@us.ibm.com \
--cc=anthony@codemonkey.ws \
--cc=kvm@vger.kernel.org \
--cc=paul@codesourcery.com \
--cc=qemu-devel@nongnu.org \
--cc=ryanh@us.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).