RE: [PATCH V10 0/6] mm: frontswap: overview (and proposal to merge at next window)

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> From: KAMEZAWA Hiroyuki [mailto:kamezawa.hiroyu@jp.fujitsu.com]
> Sent: Wednesday, September 28, 2011 12:16 AM
> To: Dan Magenheimer
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org; jeremy@goop.org; hughd@google.com;
> ngupta@vflare.org; Konrad Wilk; JBeulich@novell.com; Kurt Hackel; npiggin@kernel.dk; akpm@linux-
> foundation.org; riel@redhat.com; hannes@cmpxchg.org; matthew@wil.cx; Chris Mason;
> sjenning@linux.vnet.ibm.com; jackdachef@gmail.com; cyclonusj@gmail.com; levinsasha928@gmail.com
> Subject: Re: [PATCH V10 0/6] mm: frontswap: overview (and proposal to merge at next window)
> 
> On Thu, 15 Sep 2011 14:33:05 -0700
> Dan Magenheimer <dan.magenheimer@oracle.com> wrote:
> 
> > [PATCH V10 0/6] mm: frontswap: overview (and proposal to merge at next window)
> >
> > (Note: V9->V10 only change is corrections in debugfs-related code/counters)
> >
> > (Note to earlier reviewers:  This patchset was reorganized at V9 due
> > to feedback from Kame Hiroyuki and Andrew Morton.  Additionally, feedback
> > on frontswap v8 from Andrew Morton also applies to cleancache, to wit:
> >  (1) change usage of sysfs to debugfs to avoid unnecessary kernel ABIs
> >  (2) rename all uses of "flush" to "invalidate"
> > As a result, additional patches (5of6 and 6of6) were added to this
> > series at V9 to patch cleancache core code and cleancache hooks in the mm
> > and fs subsystems and update cleancache documentation accordingly.)
> 
> I'm sorry I couldn't catch following... what happens at hibernation ?
> frontswap is effectively stopped/skipped automatically ? or contents of
> TMEM can be kept after power off and it can be read correctly when
> resume thread reads swap ?
> 
> In short: no influence to hibernation ?
> I'm sorry if I misunderstand some.

Hi Kame --

Hibernation would need to be handled by the tmem backend (e.g. zcache, Xen
tmem).  In the case of Xen tmem, both save/restore and live migration are
fully supported.  I'm not sure if zcache works across hibernation; since
all memory is kmalloc'ed, I think it should work fine, but it would be an
interesting experiment.

Thanks,
Dan

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