Re: [PATCH] remove compaction from kswapd

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 2 Mar 2011 05:38:56 +0100 Andrea Arcangeli <aarcange@redhat.com> wrote:

> On Tue, Mar 01, 2011 at 04:41:43PM -0800, Andrew Morton wrote:
> > I'd be pretty worried about jamming this into 2.6.38 at this late
> > stage.  And some vague talk about something Arthur did really doesn't
> > help a lot!  It would be better to have some good, solid quantitative
> > justification for what is really an emergency patch.  
> 
> It is a emergency patch. This is zero risk, this brings back kswapd in
> 2.6.37 status!

The original patch description didn't explain this.

And no patch is "zero risk", especially at -rc6.

> 2.6.38 added a new feature, I'm reverting it because
> it's screwing benchmarks.

And we have no useful information about benchmark results.

> > Bear in mind that we always have a middle option: merge a patch into
> > 2.6.39-rc1 and tag it for backporting into 2.6.38.x.  That gives us
> > more time to test it and to generally give it a shakedown.  But to make
> > decisions like that and to commend a patch to the -stable maintainers,
> > we need to provide better information please.
> 
> This is 100% tested in 2.6.37. The new code was tested in 2.6.38-rc
> and testing return -EFAIL. So we must revert this change.

What change?  Commit ID?  What testing returned -EFAIL?  That's
different from slower benchmark results.

> This patch
> is doing nothing but reverting compaction-kswapd code merged in
> 2.6.38-rc. The old code is fully tested.
> 
> > Also, "This goes on top of the two lowlatency fixes for compaction"
> > isn't particularly helpful.  I need to verify that the referred-to
> > patches are already in mainline but I don't have a clue what this
> > description refers to.  More specificity, please - it helps avoid
> > mistakes.
> 
> Those two patches are fully orthogonal with this one.

*What* two patches???  I don't have a clue which patches you're referring to. 
Patches have names, please use them.

> Andrew already
> has them in -mm and there's no need to analyse those simultaneously
> with this one.
> 
> I mentioned those two because those two are also important fixes to
> avoid compaction to disable interrupts for too long, but they have no
> actual relation to this one. One of the two fixes that Mel sent was
> actually embedded into my patch but he splitted it off rightfully
> because it has no relation.

This is just hopeless.  Please, just send the thing again and this time
include a *full* description of what it does and why it does it.

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