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Date: Tue, 20 Aug 2013 09:57:38 -0700 From: Randy Dunlap <rdunlap@...radead.org> To: Cyrill Gorcunov <gorcunov@...il.com> CC: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...capital.net>, Pavel Emelyanov <xemul@...allels.com>, Matt Mackall <mpm@...enic.com>, Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>, Marcelo Tosatti <mtosatti@...hat.com>, KOSAKI Motohiro <kosaki.motohiro@...il.com>, Stephen Rothwell <sfr@...b.auug.org.au>, Peter Zijlstra <peterz@...radead.org>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> Subject: Re: [PATCH -mm] docs: Document soft dirty behaviour for freshly created memory regions On 08/20/13 08:31, Cyrill Gorcunov wrote: > Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org> > Cc: Pavel Emelyanov <xemul@...allels.com> > Cc: Andy Lutomirski <luto@...capital.net> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: Matt Mackall <mpm@...enic.com> > Cc: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> > Cc: Marcelo Tosatti <mtosatti@...hat.com> > Cc: KOSAKI Motohiro <kosaki.motohiro@...il.com> > Cc: Stephen Rothwell <sfr@...b.auug.org.au> > Cc: Peter Zijlstra <peterz@...radead.org> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> > --- > Documentation/vm/soft-dirty.txt | 7 +++++++ > 1 file changed, 7 insertions(+) > > Index: linux-2.6.git/Documentation/vm/soft-dirty.txt > =================================================================== > --- linux-2.6.git.orig/Documentation/vm/soft-dirty.txt > +++ linux-2.6.git/Documentation/vm/soft-dirty.txt > @@ -28,6 +28,13 @@ This is so, since the pages are still ma > the kernel does is finds this fact out and puts both writable and soft-dirty > bits on the PTE. > > + While in most cases tracking memory changes by #PF-s is more than enough enough, > +there is still a scenario when we can loose soft dirty bit -- a task does lose soft dirty bits -- a task > +unmap previously mapped memory region and then maps new one exactly at the unmaps a previously mapped memory region and then maps a new one at exactly the > +same place. When unmap called the kernel internally clears PTEs values When unmap is called, the kernel internally clears PTE values > +including soft dirty bit. To notify user space application about such bits. > +memory region renewal the kernel always mark new memory regions (and marks > +expanded regions) as soft dirtified. or: as soft dirty. > > This feature is actively used by the checkpoint-restore project. You > can find more details about it on http://criu.org > -- -- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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