From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Lieven <pl@kamp.de>
Subject: Re: [Bug 1100843] Re: Live Migration Causes
 Performance Issues
Date: Thu, 10 Oct 2013 10:17:35 +0200
Message-ID: <5256629F.10702@kamp.de>
References: <20130117163740.7157.55600.malonedeb@gac.canonical.com>	<20130926203354.30826.10562.malone@soybean.canonical.com>
	<52516C4A.6080508@gmail.com> <525256FC.6060608@dlhnet.de>
	<525280C7.2050402@redhat.com> <525283A6.1070605@dlhnet.de>
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Cc: kvm@vger.kernel.org, gleb@redhat.com, quintela@redhat.com,
	mtosatti@redhat.com, qemu-devel <qemu-devel@nongnu.org>,
	Zhang Haoyu <ahzhanghaoyu@gmail.com>, xiaoguangrong@linux.vnet.ibm.com,
	Bug 1100843 <1100843@bugs.launchpad.net>, mst@redhat.com, afaerber@suse.de
To: Paolo Bonzini <pbonzini@redhat.com>
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On 07.10.2013 11:55, Paolo Bonzini wrote:
> Il 07/10/2013 11:49, Peter Lieven ha scritto:
>>> It's in general not easy to do this if you take non-x86 targets into
>>> account.
>> What about the dirty way to zero out all non zero pages at the beginning of
>> ram_load?
> I'm not sure I follow?
sth like this for each ram block at the beginning of ram_load.

  
+                    base = memory_region_get_ram_ptr(block->mr);
+                    for (offset = 0; offset < block->length;
+                         offset += TARGET_PAGE_SIZE) {
+                        if (!is_zero_page(base + offset)) {
+                            memset(base + offset, 0x00, TARGET_PAGE_SIZE);
+                        }
+                    }
+

Then add a capability "skip_zero_pages" which does not sent them on the source
and enables this zeroing. it would also be possible to skip the zero check
for each incoming compressed pages.

Peter