From: Andi Kleen <ak@suse.de>
To: Alex Pankratov <ap@swapped.cc>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [2.6] [2/2] hlist: remove IFs from hlist functions
Date: 11 Feb 2004 09:55:34 +0100 [thread overview]
Message-ID: <p73y8ra5721.fsf@nielsen.suse.de> (raw)
In-Reply-To: <4029D2D5.7070504@swapped.cc.suse.lists.linux.kernel>
Alex Pankratov <ap@swapped.cc> writes:
> Stephen Hemminger wrote:
> > +++ linux-2.6.2.hlist/lib/list.c 2004-02-10 13:03:08.000000000 -0800
> >
> >> @@ -0,0 +1,10 @@
> >> +#include <linux/module.h>
> >> +#include <linux/list.h>
> >> +
> >> +/*
> >> + * shared tail sentinel for hlists
> >> + */
> >> +struct hlist_node hlist_null;
> > Could this be const?
>
> No, because its 'pprev' field *is* getting modified.
I didn't notice this before, sorry. But this could end up
being a scalability problem on big SMP systems. Even though
the cache line of this is never read it will bounce all the
time between all CPUs using hlists and add considerably
latency and cross node traffic. Remember Linux is supposed
to run well on 128 CPU machines now.
Maybe you can make it UP only, but I'm still not sure it's
worth it.
-Andi
next parent reply other threads:[~2004-02-11 8:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4029CB7E.4030003@swapped.cc.suse.lists.linux.kernel>
[not found] ` <4029CF24.1070307@osdl.org.suse.lists.linux.kernel>
[not found] ` <4029D2D5.7070504@swapped.cc.suse.lists.linux.kernel>
2004-02-11 8:55 ` Andi Kleen [this message]
2004-02-11 16:48 ` [PATCH] [2.6] [2/2] hlist: remove IFs from hlist functions Alex Pankratov
2004-02-14 18:59 ` Andi Kleen
2004-02-12 4:42 ` Alex Pankratov
2004-02-14 19:43 ` Andi Kleen
2004-02-11 6:28 Alex Pankratov
2004-02-11 6:43 ` Stephen Hemminger
2004-02-11 6:59 ` Alex Pankratov
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