From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757369AbZBSMgu (ORCPT ); Thu, 19 Feb 2009 07:36:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753165AbZBSMgl (ORCPT ); Thu, 19 Feb 2009 07:36:41 -0500 Received: from smtp115.mail.mud.yahoo.com ([209.191.84.164]:31376 "HELO smtp115.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752973AbZBSMgk (ORCPT ); Thu, 19 Feb 2009 07:36:40 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=0N8JrvDKU7JDKF5Lmrengo0IlgctrdCXV6F6nytYT+U+0LNCRw9tQEcXlilU/Y9j1KhSklATE4fn3z+wk7xnrRUo1ggNNSdTscBn4nUEMi+m0PBaV+sW347ekJpA99iBSN6LAbCZ+siebGOGcU7UpDfEincbsjKSN1W8PSPYDW8= ; X-YMail-OSG: C0VewPoVM1mujyUN8SGUCyJUrRKrHiSG1UihjkShbEaRqW2AUuZb701DgLA8AG9ljyYUqlKun.ML9c1x7Vp_WNqy7w9zHJqFEsVfwE8F9o6UG6U2M0Owyl.yCvJW3Hg23FS9USV0Cut9WKtN_AOce2YeYiqVZea8nDYzY5poAMLSwCe8yw0SvdcK.4Jy5g-- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Tejun Heo Subject: Re: [PATCH 09/10] percpu: implement new dynamic percpu allocator Date: Thu, 19 Feb 2009 23:36:01 +1100 User-Agent: KMail/1.9.51 (KDE/4.0.4; ; ) Cc: rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, jeremy@goop.org, cpw@sgi.com, mingo@elte.hu References: <1234958676-27618-1-git-send-email-tj@kernel.org> <1234958676-27618-10-git-send-email-tj@kernel.org> In-Reply-To: <1234958676-27618-10-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200902192336.02800.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 18 February 2009 23:04:35 Tejun Heo wrote: > Impact: new scalable dynamic percpu allocator which allows dynamic > percpu areas to be accessed the same way as static ones > > Implement scalable dynamic percpu allocator which can be used for both > static and dynamic percpu areas. This will allow static and dynamic > areas to share faster direct access methods. This feature is optional > and enabled only when CONFIG_HAVE_DYNAMIC_PER_CPU_AREA is defined by > arch. Please read comment on top of mm/percpu.c for details. Seems pretty nice. Wishlist: would be cool to have per-cpu virtual memory mappings and do CPU-local percpu access via a single pointer. Of course there would need to be some machinery and maybe a new API to be more careful about accessing remote percpu data (that access could perhaps just be slower and go via the linear mapping). It would probably be quite a bit slower to do remote percpu access, but some users never do this remote access in fastpath, and want really fast local access (eg slab allocators). I guess the hardest part would be doing the arch code.