[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-ppc] broken incoming migration

From: Paolo Bonzini
Subject: Re: [Qemu-ppc] broken incoming migration
Date: Thu, 30 May 2013 16:08:51 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6

Il 30/05/2013 15:38, Alexey Kardashevskiy ha scritto:
>>> does this problem only occur on pseries emulation?
>> Probably not.  On a PC, it would occur if you had 4K of zeros in the
>> source BIOS but not in the destination BIOS.  When you reboot, the BIOS
>> image is wrong.
>>> not sending zero pages is not only a performance benefit it also makes
>>> overcomitted memory usable. the madv_dontneed seems to kick in 
>>> asynchronously
>>> and memory is not available immediately.
>> You could also scan the page for nonzero values before writing it.
> Scan where? On the source? It is there already. On the destination? Won't
> just trying to read a page kill all effect from MADV_DONTNEED?

No, zero pages are handled with special copy-on-write magic by the
kernel. :)  So, reading works but writing doesn't.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]