From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] use local_t for page statistics Date: Sat, 7 Jan 2006 04:25:24 +0100 References: <20060106215332.GH8979@kvack.org> <200601070401.47618.ak@suse.de> <43BF3355.5060606@yahoo.com.au> In-Reply-To: <43BF3355.5060606@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200601070425.24810.ak@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , Benjamin LaHaise , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Saturday 07 January 2006 04:19, Nick Piggin wrote: > Andi Kleen wrote: > > On Saturday 07 January 2006 03:52, Nick Piggin wrote: > > > > > >>No. On many load/store architectures there is no good way to do local_t, > >>so something like ppc32 or ia64 just uses all atomic operations for > > > > > > well, they're just broken and need to be fixed to not do that. > > > > How? If anything use the 3x duplicated data setup, not atomic operations. > > > Also I bet with some tricks a seqlock like setup could be made to work. > > > > I asked you how before. If you can come up with a way then it indeed > might be a good solution... I'll try to work something up. > The problem I see with seqlock is that it > is only fast in the read path. That path is not the issue here. The common case - not getting interrupted would be fast. > > > >>local_t, and ppc64 uses 3 counters per-cpu thus tripling the cache > >>footprint. > > > > > > and ppc64 has big caches so this also shouldn't be a problem. > > > > Well it is even less of a problem for them now, by about 1/3. > > Performance-wise there is really no benefit for even i386 or x86-64 > to move to local_t now either so I don't see what the fuss is about. Actually P4 doesn't like CLI/STI. For AMD and P-M it's not that much an issue, but NetBurst really doesn't like it. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org