linux-kernel - Re: [PATCH 1/1] suspend: make sync() on suspend-to-RAM optional

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Date:	Wed, 15 Jul 2015 10:06:54 -0400
From:	Austin S Hemmelgarn <ahferroin7@...il.com>
To:	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>
CC:	rjw@...ysocki.net, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] suspend: make sync() on suspend-to-RAM optional

On 2015-07-15 02:43, Pavel Machek wrote:
> On Tue 2015-07-14 22:24:51, Len Brown wrote:
>> From: Len Brown <len.brown@...el.com>
>>
>> The Linux kernel suspend path has traditionally invoked sys_sync().
>>
>> But sys_sync() can be expensive, and some systems do not want
>> to pay the cost of sys_sync() on every suspend.
>
> Have you measured how expesive it can be, and why it is expensive?
How expensive it is can vary widely, but it pretty much boils down to 
how much dirty data still needs written out, and how slow the storage it 
needs written to is.  There's not really much that can be done in the 
kernel to change this, and most userspace suspend systems call sync 
themselves during the suspend sequence.


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