From: Paolo Bonzini <pbonzini@redhat.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: Orit Wasserman <owasserm@redhat.com>, Peter Lieven <pl@dlhnet.de>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] RFC migration of zero pages
Date: Fri, 01 Feb 2013 17:58:28 +0100 [thread overview]
Message-ID: <510BF434.1010308@redhat.com> (raw)
In-Reply-To: <20130131094809.GO15004@redhat.com>
Il 31/01/2013 10:48, Gleb Natapov ha scritto:
>> Also I notice that the bottle neck in migrating unmapped pages is the detection of those pages
>> because we map the pages in order to check them, for a large guest this is very expensive as mapping a page
>> results in a page fault in the host.
>> So what will be very helpful is actually locating those pages without mapping them
>> which looks very complicated.
>>
> What is wrong with mincore()?
As Avi said, it returns false if the memory is in swap.
Note that while we do take a page fault, the recent kernel patch to
introduce a huge zero page might have reduced the cost in terms of both
clear_page and cache misses.
Paolo
next prev parent reply other threads:[~2013-02-01 16:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <510A15DC.3070706@dlhnet.de>
[not found] ` <510A218C.2000903@redhat.com>
[not found] ` <20130131094809.GO15004@redhat.com>
[not found] ` <510A47F1.6070302@redhat.com>
[not found] ` <CAEbWaipEYFLshmMxm3R+n=Kk+ya7+m0-B5K__2RqeMM_vex4SA@mail.gmail.com>
[not found] ` <20130131143043.GD23213@redhat.com>
[not found] ` <CAEbWaiqJ1pjaXeBtqf7Ww-KX8x7t+bvn6JzhPr8KbtA6ADBH1g@mail.gmail.com>
[not found] ` <20130131144243.GE23213@redhat.com>
[not found] ` <CAEbWaio1SM3u=-_paMkU6sLK1SWih0_gUgMDQhJ-N37dTuX4=Q@mail.gmail.com>
[not found] ` <20130131211844.GC16941@redhat.com>
2013-02-01 7:30 ` [Qemu-devel] RFC migration of zero pages Avi Kivity
2013-02-01 16:58 ` Paolo Bonzini [this message]
[not found] ` <85C05B4E-E6BC-43D3-917F-E3EAC674F2EA@dlhnet.de>
[not found] ` <510A2C3D.3060001@redhat.com>
2013-02-01 17:03 ` Paolo Bonzini
2013-02-03 7:24 ` Peter Lieven
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