linux-kernel - Re: [PATCH] slub: Disable the lockless allocator

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Message-ID: <AANLkTin8jHz0a5oS4LWQCrYW2VDb9A0V2aL7O5dYaPBt@mail.gmail.com>
Date:	Sat, 26 Mar 2011 12:30:36 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	akpm@...ux-foundation.org, tj@...nel.org, npiggin@...nel.dk,
	rientjes@...gle.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] slub: Disable the lockless allocator

On Sat, Mar 26, 2011 at 12:18 PM, Christoph Lameter <cl@...ux.com> wrote:
>
> Right. RSI should be in the range of the values you printed.
> However, the determination RSI is independent of the emulation of the
> instruction. If RSI is set wrong then we should see these failures on
> machines that do not do the instruction emulation. A kvm run with Ingo's
> config should show the same issues. Will do that now.

I bet it's timing-dependent and/or dependent on some code layout
issue. Why else would the totally pointless previous patch have made
any difference for Ingo (the "SLUB: Write to per cpu data when
allocating it" thing seems to be pure voodoo programming)?

That said, this early in the boot I don't think we should have any
parallelism going on, so I don't see what could make those kinds of
random effects.

                             Linus
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