From: Marc Zyngier <marc.zyngier@arm.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Subject: Re: [PATCH 0/4] irqchip/gic-v3-its: free_lpi_range tweaks
Date: Tue, 12 Mar 2019 18:03:13 +0000 [thread overview]
Message-ID: <e0a7becd-9098-e264-b509-a6bcd5279a7a@arm.com> (raw)
In-Reply-To: <20190312173350.4025-1-linux@rasmusvillemoes.dk>
Hi Rasmus,
On 12/03/2019 17:33, Rasmus Villemoes wrote:
> I noticed that the O(n log n) behaviour of free_lpi_range could easily
> be made O(n) (patch 4), though I don't suppose n is ever large enough
> to actually matter. While there, I also stumbled on two other
> micro-optimizations (2 and 3).
n is usually in the range 1 .. nr_cpus, so pretty small, even on the
biggest machines we have around (256 threads). And actually, nobody ever
frees LPIs, because hey, why would you?
> Then while writing the commit log for the last patch, I noticed that
> the cmp callback I was removing was actually buggy, so I went back and
> added a patch in front suitable for -stable. I'll leave it to others
> to decide if it's important enough for that.
Thanks for that. I'll have a look at the whole thing anyway (I've just
glanced over it so far).
> Please note that this is only compile-tested.
Right, this needs some actual testing then. /me needs to build a guest
that shakes the allocator a bit.
Cheers,
M.
--
Jazz is not dead. It just smells funny...
prev parent reply other threads:[~2019-03-12 18:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-12 17:33 Rasmus Villemoes
2019-03-12 17:33 ` [PATCH 1/4] irqchip/gic-v3-its: fix comparison logic in lpi_range_cmp Rasmus Villemoes
2019-03-12 17:33 ` [PATCH 2/4] irqchip/gic-v3-its: move allocation outside mutex Rasmus Villemoes
2019-03-12 17:33 ` [PATCH 3/4] irqchip/gic-v3-its: drop redundant initialization in mk_lpi_range Rasmus Villemoes
2019-03-12 17:33 ` [PATCH 4/4] irqchip/gic-v3-its: make free_lpi_range a little cheaper Rasmus Villemoes
2019-03-12 18:03 ` Marc Zyngier [this message]
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