linux-kernel - RE: [PATCH] bdi: use deferable timer for sync

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Message-ID: <1286533687.2095.58.camel@localhost>
Date:	Fri, 08 Oct 2010 13:28:07 +0300
From:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
To:	"Wu, Xia" <xia.wu@...el.com>
Cc:	Christoph Hellwig <hch@....de>,
	Yong Wang <yong.y.wang@...ux.intel.com>,
	Jens Axboe <jaxboe@...ionio.com>,
	"Wu, Fengguang" <fengguang.wu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: [PATCH] bdi: use deferable timer for sync_supers task

On Fri, 2010-10-08 at 18:27 +0800, Wu, Xia wrote:
> > However, when the next wake-up interrupt happens is not defined. It can
> > happen 1ms after, or 1 minute after, or 1 hour after. What Christoph
> > says is that there should be some guarantee that sb writeout starts,
> > say, within 5 to 10 seconds interval. Deferrable timers do not guarantee
> > this. But take a look at the range hrtimers - they do exactly this.
> 
> If the system is in sleep state, is there any data which should be written?

May be yes, may be no.

>  Must 
> sb writeout start even there isn't any data? 

No.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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