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Message-ID: <2293886.L6VJGgjdDp@vostro.rjw.lan>
Date: Mon, 06 Jul 2015 01:28:20 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Dave Chinner <david@...morbit.com>, Len Brown <lenb@...nel.org>,
Henrique de Moraes Holschuh <hmh@....eng.br>,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
Linux PM list <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] suspend: delete sys_sync()
On Saturday, July 04, 2015 10:19:55 AM Alan Stern wrote:
> On Sat, 4 Jul 2015, Rafael J. Wysocki wrote:
>
> > The only argument against dropping sys_sync() from the suspend code path
> > I've seen in this thread that I entirely agree with is that it may lead to
> > regressions, because we've done it practically forever and it may hide latent
> > bugs somewhere in block drivers etc. Dropping it, though, is the only way
> > to see those bugs, if any, and if we want to ever fix them, we need to see
> > them. That's why I think that it may be a good idea to allow people to
> > drop it if they are willing to accept some extra risk (via the kernel
> > command line, for example).
>
> I'd be perfectly happy to have the sync selectable at runtime, one way
> or another. The three most reasonable options seem to be:
>
> kernel command line
>
> sysfs file
>
> sysctl setting
>
> The command line is less flexible (it can't be changed after booting).
> Either of the other two would be fine with me.
We'll probably use a sysfs file (possibly plus a Kconfig option to set the
boot time default).
> > Moreover, question is if we really need to carry out the sync on *every*
> > suspend even if it is not pointless overall. That shouldn't really be
> > necessary if we suspend and resume often enough or if we resume only for
> > a while and then suspend again. Maybe it should be rate limited somehow
> > at least?
>
> For example, skip the sync if the system has been awake for < 100 ms?
Yes, something like that.
> The cutoff time could also be controlled by the sysfs file: -1 =>
> never sync, 0 => always sync, > 0 => sync if the system has been awake
> longer than the value.
That sounds like a good idea to me.
Thanks,
Rafael
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