linux-kernel - Re: [PATCH v2] PM: HIBERNATION: skip the swap size check if the snapshot image size is anticipative

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Message-Id: <201201092246.35170.rjw@sisk.pl>
Date:	Mon, 9 Jan 2012 22:46:34 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Barry Song <21cnbao@...il.com>
Cc:	Pavel Machek <pavel@....cz>, Barry Song <Barry.Song@....com>,
	linux-pm@...ts.linux-foundation.org, workgroup.linux@....com,
	Xiangzhen Ye <Xiangzhen.Ye@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Barry Song <Baohua.Song@....com>
Subject: Re: [PATCH v2] PM: HIBERNATION: skip the swap size check if the snapshot image size is anticipative

On Monday, January 09, 2012, Barry Song wrote:
> 2012/1/9 Rafael J. Wysocki <rjw@...k.pl>:
> > On Friday, January 06, 2012, Barry Song wrote:
> >> 2012/1/6 Pavel Machek <pavel@....cz>:
> >> > Hi!
> >> >
> >> > Is the check even useful these days? Should we remove it altogether?
> >>
> >> i think we can let users or distributions decide whether it is useful.
> >> On PC, disk space is not an issue, people might run many applications
> >> while doing hibernation, so snapshot is much big. an early check will
> >> improve user experience because people don't need to wait a long time
> >> and find space is not enough.
> >> for embedded system, SoC solutions can know whether the space is
> >> enough since they know what are running while doing hibernation, so
> >> they can skip the check by setting the flag in sysfs.
> >> that is why i had this patch sent.
> >
> > I agree with Pavel that it's better to drop the check altogether.
> >
> > The sysfs switch you're adding doesn't seem to be very useful, as PC
> > users won't touch it and whoever needs it to be 0, will always set it
> > that way and won't change it afterwards.
> 
> ok. if we don't have the check, in case swap partition is not enough,
> writing failure will happen, system still can restore to normal
> status:
> 
> for example, in the following test, only 27% data is written with a
> small partition, "Restarting tasks ... done" will make system restore
> to normal status.
> 
> [   11.2080 27%
> [   11.403274] PM: Wrote uncompressed 34920 kbytes in 0.65 seconds (53.72 MB/s)
> [   11.407649] PM: Wrote compressed 3500 kbytes in 0.65 seconds (5.38 MB/s)
> [   11.447176] Restarting tasks ... done.
> [   11.448801] ...

That's exactly correct.

Thanks,
Rafael
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