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From: Nick Piggin <npiggin@kernel.dk>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Nick Piggin <npiggin@kernel.dk>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 3/3] brlocks/lglocks: turn into functions
Date: Fri, 20 Apr 2012 21:21:49 +1000	[thread overview]
Message-ID: <20120420112149.GH25458@amd.local0.net> (raw)
In-Reply-To: <87ipijzfwn.fsf@rustcorp.com.au>

This still not merged?

On Mon, Mar 05, 2012 at 05:35:28PM +1030, Rusty Russell wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> lglocks and brlocks are currently generated with some complicated macros
> in lglock.h.  But there's no reason to not just use common utility
> functions and put all the data into a common data structure.

There is a reason, which is performance. Extra function call, but also
IIRC the percpu accessor was not so fast doing it this way. Maybe
that's improved...

So what's the performance difference?

> 
> Since there are at least two users it makes sense to share this code in a
> library.  This is also easier maintainable than a macro forest.
> 
> This will also make it later possible to dynamically allocate lglocks and
> also use them in modules (this would both still need some additional, but
> now straightforward, code)

Yes, but let's not do either of those things :)

I was slightly crazy when committing that patch to the kernel, I'll
admit. So if performance isn't significantly affected, then definitely.
If it is... well, it's much easier to gain 1% performance by maintaining
100 self contained lines of hilarious code like this than to actually
use your brain to improve somewhere else!

Thanks,
Nick

  reply	other threads:[~2012-04-20 11:22 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-27 23:22 [PATCH] cpumask: fix lg_lock/br_lock Rusty Russell
2012-02-27 23:53 ` Andrew Morton
2012-02-27 23:53   ` Andrew Morton
2012-02-28  8:43   ` Ingo Molnar
2012-02-28 11:25     ` Andi Kleen
2012-02-28 12:51       ` Ingo Molnar
2012-02-28 21:27     ` Andrew Morton
2012-02-29  5:44       ` Srivatsa S. Bhat
2012-02-29  9:17         ` Ingo Molnar
2012-02-29 11:12           ` Srivatsa S. Bhat
2012-03-01  7:38             ` Ingo Molnar
2012-03-01  9:15               ` Srivatsa S. Bhat
2012-03-01  9:45                 ` Ingo Molnar
2012-03-01  9:56                   ` Srivatsa S. Bhat
2012-03-01  8:12             ` Srivatsa S. Bhat
2012-03-01  8:24               ` Srivatsa S. Bhat
2012-03-01  8:12               ` Srivatsa S. Bhat
2012-03-01  8:15               ` [PATCH 1/3] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
2012-03-01  8:27                 ` Srivatsa S. Bhat
2012-03-01  8:15                 ` Srivatsa S. Bhat
2012-03-01  8:16               ` [PATCH 2/3] CPU hotplug, arch/powerpc: Fix CPU hotplug " Srivatsa S. Bhat
2012-03-01  8:28                 ` Srivatsa S. Bhat
2012-03-01  8:16                 ` Srivatsa S. Bhat
2012-03-01  8:18               ` [PATCH 3/3] CPU hotplug, arch/sparc: " Srivatsa S. Bhat
2012-03-01  8:30                 ` Srivatsa S. Bhat
2012-03-01  8:18                 ` Srivatsa S. Bhat
2012-02-29  8:29       ` [PATCH] cpumask: fix lg_lock/br_lock Ingo Molnar
2012-02-29  8:58         ` Peter Zijlstra
2012-02-29  9:32           ` Ingo Molnar
2012-02-28 11:24   ` Andi Kleen
2012-03-05  7:02     ` Rusty Russell
2012-03-05  7:03     ` [PATCH 1/3] lglock: remove online variants of lock Rusty Russell
2012-04-20 11:12       ` Nick Piggin
2012-03-05  7:04     ` [PATCH 2/3] brlocks/lglocks: API cleanups Rusty Russell
2012-03-05  7:05     ` [PATCH 3/3] brlocks/lglocks: turn into functions Rusty Russell
2012-04-20 11:21       ` Nick Piggin [this message]
2012-05-07  3:39         ` Rusty Russell
2012-05-07  5:46           ` Al Viro
2012-05-08  3:59             ` [PATCH 1/3] lglock: remove online variants of lock Rusty Russell
2012-05-08  4:50               ` Al Viro
2012-05-08  6:12                 ` Rusty Russell
2012-05-08  4:02             ` [PATCH 2/3] brlocks/lglocks: API cleanups Rusty Russell
2012-05-08  4:02             ` [PATCH 3/3] brlocks/lglocks: turn into functions Rusty Russell
2012-05-09  7:35           ` Nick Piggin
2012-05-09  7:35             ` Nick Piggin

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