From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 23 Apr 2009 02:44:51 +0100 (BST) Received: from sj-iport-6.cisco.com ([171.71.176.117]:28432 "EHLO sj-iport-6.cisco.com") by ftp.linux-mips.org with ESMTP id S29571309AbZDVSE5 (ORCPT ); Wed, 22 Apr 2009 19:04:57 +0100 X-IronPort-AV: E=Sophos;i="4.40,231,1238976000"; d="scan'208";a="290940698" Received: from sj-dkim-2.cisco.com ([171.71.179.186]) by sj-iport-6.cisco.com with ESMTP; 22 Apr 2009 18:04:48 +0000 Received: from sj-core-1.cisco.com (sj-core-1.cisco.com [171.71.177.237]) by sj-dkim-2.cisco.com (8.12.11/8.12.11) with ESMTP id n3MI4lod032264; Wed, 22 Apr 2009 11:04:48 -0700 Received: from cliff.cisco.com (cliff.cisco.com [171.69.11.141]) by sj-core-1.cisco.com (8.13.8/8.13.8) with ESMTP id n3MI4lKu001328; Wed, 22 Apr 2009 18:04:47 GMT Received: from cuplxvomd02.corp.sa.net ([64.101.20.155]) by cliff.cisco.com (8.6.12/8.6.5) with ESMTP id SAA27575; Wed, 22 Apr 2009 18:04:47 GMT Date: Wed, 22 Apr 2009 11:04:47 -0700 From: David VomLehn To: David Daney Cc: linux-mips@linux-mips.org, Ralf Baechle Subject: Re: [PATCH 0/2] MIPS: Move signal return trampolines off the stack. Message-ID: <20090422180447.GC28623@cuplxvomd02.corp.sa.net> References: <49EE3B0F.3040506@caviumnetworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49EE3B0F.3040506@caviumnetworks.com> User-Agent: Mutt/1.5.18 (2008-05-17) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; l=1183; t=1240423488; x=1241287488; c=relaxed/simple; s=sjdkim2002; h=Content-Type:From:Subject:Content-Transfer-Encoding:MIME-Version; d=cisco.com; i=dvomlehn@cisco.com; z=From:=20David=20VomLehn=20 |Subject:=20Re=3A=20[PATCH=200/2]=20MIPS=3A=20Move=20signal =20return=20trampolines=20off=20the=20stack. |Sender:=20; bh=jhHO92VnA3I6Qsv5v4n6kn+lZierwWpDxADI99XzRz8=; b=R88WL/XCxkfHY+juI541CkXJWyM6a/x6GViJbCO6Ig8ln8oybS7HqMpJn2 Ib5sgJzAefMRAV120b++8EY3IMrfaXMOIVUids+9VoAyYUFGX57XLYiLzPuN 6hbbQ6jaAr; Authentication-Results: sj-dkim-2; header.From=dvomlehn@cisco.com; dkim=pass ( sig from cisco.com/sjdkim2002 verified; ); Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 22424 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: dvomlehn@cisco.com Precedence: bulk X-list: linux-mips On Tue, Apr 21, 2009 at 02:30:55PM -0700, David Daney wrote: > This patch set (against 2.6.29.1) creates a vdso and moves the signal > trampolines to it from their previous home on the stack. > > Tested with a 64-bit kernel on a Cavium Octeon cn3860 where I have the > following results from lmbench2: > > Before: > n64 - Signal handler overhead: 14.517 microseconds > n32 - Signal handler overhead: 14.497 microseconds > o32 - Signal handler overhead: 16.637 microseconds > > After: > > n64 - Signal handler overhead: 7.935 microseconds > n32 - Signal handler overhead: 7.334 microseconds > o32 - Signal handler overhead: 8.628 microseconds Nice numbers, and something that will be even more critical as real-time features are added and used! > Comments encourged. Only one comment, which I would not want to hold up acceptance: based on some numbers sent out recently, it looks like the kernel is experiencing some performance issues with exec() and I think this change will make it slightly slower. You could avoid this by deferring installation of the trampoline to the first use of a system call that registers a signal handler. David VomLehn