linux-kernel - Re: [PATCH 0/4] irqchip/gic-v3-its: free_lpi

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Message-ID: <e0a7becd-9098-e264-b509-a6bcd5279a7a@arm.com>
Date:   Tue, 12 Mar 2019 18:03:13 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH 0/4] irqchip/gic-v3-its: free_lpi_range tweaks

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...