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Date: Sun, 10 Oct 2010 20:07:34 +0100
From: Alasdair G Kergon <agk@...hat.com>
To: Andi Kleen <andi@...stfloor.org>
Cc: Milan Broz <mbroz@...hat.com>, Mike Snitzer <snitzer@...hat.com>,
Andi Kleen <ak@...ux.intel.com>,
device-mapper development <dm-devel@...hat.com>,
pedrib@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] DM-CRYPT: Scale to multiple CPUs v3
> > AFAIK Nested dm-crypt is not extreme for some folk who have routine
> > configurations using it. But if in_interrupt is set how does this code
^^^^^^^^^^^
> > work for them now compared to how it worked before?
On Sun, Oct 10, 2010 at 08:51:00PM +0200, Andi Kleen wrote:
> Previously they will all pile up on the single worker thread.
> Now in the nested case the nested work is run in their own
> context. This should actually scale better because you
> get parallelism too, not contention on a single resource.
Not if in_interrupt is set though?
+ if (per_cpu(io_wq_cpu, cpu) == current && !in_interrupt()) {
What I am missing here?
(And assume there is only 1 CPU too for worst case behaviour, presumably.)
Alasdair
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