From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763524AbYESUMN (ORCPT ); Mon, 19 May 2008 16:12:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759653AbYESUL5 (ORCPT ); Mon, 19 May 2008 16:11:57 -0400 Received: from outbound-mail-137.bluehost.com ([67.222.39.27]:51224 "HELO outbound-mail-137.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758526AbYESUL4 (ORCPT ); Mon, 19 May 2008 16:11:56 -0400 From: Jesse Barnes To: Hidetoshi Seto Subject: Re: [PATCH] msi: skip calling pci_find_capability from msi_set_mask_bits Date: Mon, 19 May 2008 13:11:45 -0700 User-Agent: KMail/1.9.9 Cc: Arnaldo Carvalho de Melo , Matthew Wilcox , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-rt-users@vger.kernel.org References: <20080515160426.GD14846@ghostprotocols.net> <200805161044.34938.jbarnes@virtuousgeek.org> <48310691.9050706@jp.fujitsu.com> In-Reply-To: <48310691.9050706@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200805191311.46162.jbarnes@virtuousgeek.org> X-Identified-User: {642:box128.bluehost.com:virtuous:virtuousgeek.org} {sentby:smtp auth 75.111.27.49 authed with jbarnes@virtuousgeek.org} DomainKey-Status: no signature Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, May 18, 2008 9:48 pm Hidetoshi Seto wrote: > Jesse Barnes wrote: > > Since we know MSI is a problem, let's just go with fixing that for now. > > If we find that other caps are also causing problems we can revisit > > caching all of them; the patch is simple enough. > > Humm... > I suppose it can be more simple. How about this patch? > > > everytime handle_edge_irq is called it needs to mask and unmask MSI, and > > that leads to a series of very expensive calls to pci_find_capability > > The position of MSI capability is already cached in the msi_desc when > we enter the msi_set_mask_bits(). Use it instead. > > Signed-off-by: Hidetoshi Seto Yeah, this looks really nice. It should also fix Arnaldo's latency problem, and really looks like a bug fix for the MSI code more than anything. Arnaldo, can you take a look & test and ack/nack? Thanks, Jesse