From: Michael Roth <mdroth@linux.vnet.ibm.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Blue Swirl" <blauwirbel@gmail.com>,
"Andreas Färber" <andreas.faerber@web.de>,
"Anthony Liguori" <aliguori@us.ibm.com>,
"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] add MADV_DONTFORK to guest physical memory
Date: Wed, 05 Jan 2011 12:02:20 -0600 [thread overview]
Message-ID: <4D24B22C.4010302@linux.vnet.ibm.com> (raw)
In-Reply-To: <20110105151012.GC15823@random.random>
On 01/05/2011 09:10 AM, Andrea Arcangeli wrote:
> The bug is still there so I rediffed the old patch against current
> code.
>
> On a related topic: could somebody give me advice on how to implement
> a command line (command line seems enough, the other option would be
> monitor command) to make the MADV_MERGEABLE conditional? I got KSM on
> THP working fine but KSM may decrease performance by increasing the
> number of copy on write and by splitting hugepages, so we'd like to be
> able to turn off KSM on a per-VM basis (not on the whole host, which
> of course we already can by setting /sys/kernel/mm/ksm/run to 0) so
> that high perf VMs will keep running at maximum speed with KSM off but
> others may still benefit from KSM. For that I need to make the below
> MADV_MERGEABLE madvise conditional to something and the code itself
> will be trivial, we've just to converge on a command line option
> (hopefully quickly ;).
There was a -mem_prealloc option added a while back to set MAP_POPULATE
on memory mapped in via the -mem-path option. So an analogous
-mem_nomerge option or something along that line seems reasonable for
conditionally unsetting QEMU_MADV_MERGEABLE.
And for consistency you should probably make both your proposed changes
for -mem-path'd memory as well.
next prev parent reply other threads:[~2011-01-05 18:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-15 17:08 [Qemu-devel] [PATCH] add MADV_DONTFORK to guest physical memory Andrea Arcangeli
2010-09-15 17:34 ` Alexander Graf
2010-09-15 17:37 ` Andreas Färber
2011-01-05 15:10 ` Andrea Arcangeli
2011-01-05 18:02 ` Michael Roth [this message]
2011-01-05 19:44 ` Alexander Graf
2011-01-05 19:54 ` Andrea Arcangeli
2011-01-05 20:00 ` Alexander Graf
2011-01-05 20:12 ` Anthony Liguori
2011-01-05 20:15 ` Andrea Arcangeli
2011-01-05 20:26 ` Michael Roth
2011-01-05 20:35 ` Andrea Arcangeli
2011-01-05 21:27 ` Michael Roth
2011-01-06 17:49 ` Andrea Arcangeli
2011-01-06 20:49 ` Michael Roth
2011-01-05 20:10 ` Anthony Liguori
2010-09-15 21:03 ` [Qemu-devel] " Michael S. Tsirkin
2010-09-16 6:51 ` Gleb Natapov
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