On Wed, 28 Sep 2011 07:09:18 -0700 (PDT)
Dan Magenheimer [off-list ref] wrote:

quoted

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 [off-list ref] wrote:

quoted

[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.

I'm afraid that users will lose data on memory of frontswap/zcache/tmem
by power-off, hibernation. How about adding internal hooks to disable/sync
frontswap itself before hibernation ? difficult ?

Thanks,
-Kame



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