From: Peter Lieven <pl@kamp.de>
To: quintela@redhat.com
Cc: pbonzini@redhat.com, haoyu.zhang@huawei.com,
qemu-devel@nongnu.org, afaerber@suse.de,
xiaoguangrong@linux.vnet.ibm.com
Subject: Re: [Qemu-devel] [RESEND][PATCH] migration: drop MADVISE_DONT_NEED for incoming zero pages
Date: Mon, 04 Nov 2013 10:29:25 +0100 [thread overview]
Message-ID: <527768F5.5080909@kamp.de> (raw)
In-Reply-To: <87d2mvouc5.fsf@elfo.elfo>
On 24.10.2013 12:07, Juan Quintela wrote:
> Peter Lieven <pl@kamp.de> wrote:
>> The madvise for zeroed out pages was introduced when every transferred
>> zero page was memset to zero and thus allocated. Since commit
>> 211ea740 we check for zeroness of a target page before we memset
>> it to zero. Additionally we memmap target memory so it is essentially
>> zero initialized (except for e.g. option roms and bios which are loaded
>> into target memory although they shouldn't).
>>
>> It was reported recently that this madvise causes a performance degradation
>> in some situations. As the madvise should only be called rarely and if it's called
>> it is likely on a busy page (it was non-zero and changed to zero during migration)
>> drop it completely.
> Reviewed-by: Juan Quintela <quintela@redhat.com>
>
> I take it. I am on KVM Forum/LinuxCon this week. Will send when back
> at home.
Ping
Peter
next prev parent reply other threads:[~2013-11-04 9:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-24 7:21 [Qemu-devel] [RESEND][PATCH] migration: drop MADVISE_DONT_NEED for incoming zero pages Peter Lieven
2013-10-24 9:14 ` [Qemu-devel] [RESEND][PATCH 1.7] " Paolo Bonzini
2013-11-18 12:48 ` Peter Lieven
2013-11-18 16:10 ` Paolo Bonzini
2013-10-24 10:07 ` [Qemu-devel] [RESEND][PATCH] " Juan Quintela
2013-11-04 9:29 ` Peter Lieven [this message]
2013-10-30 3:08 ` Zhanghaoyu (A)
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