lkml.org 
[lkml]   [2009]   [Apr]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Ext4 and the "30 second window of death"
On Thu, Apr 02, 2009 at 05:59:53PM -0700, david@lang.hm wrote:

> is laptop mode
>
> A. "write everything now, don't delay writes" in the hope that the drive
> will be idle enough later to spin down

laptop-mode doesn't delay writes. Ever.

> or
>
> B. "delay all writes until later, then when the drive wakes up do all
> pending writes at that time" so that the drive can go to sleep in the
> meantime?

Yes.

> I've heard things in these threads that would indicate both behaviors.

The code's pretty trivial. The only real functional differences
laptop-mode brings are to write out all dirty pages (rather than just
writing down to the watermark) and to call sys_sync() a few seconds
after the last thing that hit disk rather than being satisfied from
cache. It's entirely a mechanism to opportunistically take advantage of
the disk being spun up.

--
Matthew Garrett | mjg59@srcf.ucam.org


\
 
 \ /
  Last update: 2009-04-03 03:11    [W:1.443 / U:0.884 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site