linux-kernel - Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up

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Message-ID: <20161026230726.GF2699@techsingularity.net>
Date:   Thu, 27 Oct 2016 00:07:26 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bob Peterson <rpeterso@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up_bit

On Wed, Oct 26, 2016 at 03:09:41PM -0700, Linus Torvalds wrote:
> On Wed, Oct 26, 2016 at 3:03 PM, Mel Gorman <mgorman@...hsingularity.net> wrote:
> >
> > To be clear, are you referring to PeterZ's patch that avoids the lookup? If
> > so, I see your point.
> 
> Yup, that's the one. I think you tested it. In fact, I'm sure you did,
> because I remember seeing performance numbers from  you ;)
> 

Yeah and the figures were fine. IIRC, 32-bit support was the main thing
that was missing but who cares, 32-bit is not going to have the NUMA issues
in any way that matters.

> So yes, I'd expect my patch on its own to quite possibly regress on
> NUMA systems (although I wonder how much),

I doubt it's a lot. Even if it does, it's doesn't matter because it's a
functional fix.

> but I consider PeterZ's
> patch the fix to that, so I wouldn't worry about it.
> 

Agreed. Peter, do you plan to finish that patch?

-- 
Mel Gorman
SUSE Labs