Re: [PATCH 00/23] per device dirty throttling -v8

Bill Davidsen
2007-08-10T00:21:22Z

Andrew Morton wrote:
> On Wed, 08 Aug 2007 14:10:15 -0700
> "Martin J. Bligh" <mbligh@mbligh.org> wrote:
>
>> Why isn't this easily fixable by just adding an additional dirty
>> flag that says atime has changed? Then we only cause a write
>> when we remove the inode from the inode cache, if only atime
>> is updated.
>
> I think that could be made to work, and it would fix the performance
> issue.
>
> It is a behaviour change. At present ext3 (for example) commits everything
> every five seconds. After a change like this, a crash+recovery could cause
> a file's atime to go backwards by an arbitrarily large time interval - it
> could easily be months.
>
I would think that (really) updating atime on open would be enough,
hopefully without being too much. The "lazyatime" thing I was playing
with only updated on open, final close, write, and fork.

I like the idea of updating once in a while, but one of the benefits of
noatime is allowing drives to spin down via inactivity. If something
does get done in the area of less but non-zero atime tracking, perhaps
that could be taken into account. I have to check what "laptop_mode
actually does, since my laptops are old installs.

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot