Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 5 Aug 2002 10:56:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 5 Aug 2002 10:56:34 -0400 Received: from bitmover.com ([192.132.92.2]:49559 "EHLO bitmover.com") by vger.kernel.org with ESMTP id ; Mon, 5 Aug 2002 10:56:33 -0400 Date: Mon, 5 Aug 2002 07:59:51 -0700 From: Larry McVoy To: Ingo Molnar Cc: Andi Kleen , Richard Zidlicky , Jeff Dike , Alan Cox , linux-kernel@vger.kernel.org Subject: Re: context switch vs. signal delivery [was: Re: Accelerating user mode linux] Message-ID: <20020805075951.L28512@work.bitmover.com> Mail-Followup-To: Larry McVoy , Ingo Molnar , Andi Kleen , Richard Zidlicky , Jeff Dike , Alan Cox , linux-kernel@vger.kernel.org References:

Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: ; from mingo@elte.hu on Mon, Aug 05, 2002 at 12:40:54PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 34 > > > actually the opposite is true, on a 2.2 GHz P4: > > > > > > $ ./lat_sig catch > > > Signal handler overhead: 3.091 microseconds > > > > > > $ ./lat_ctx -s 0 2 > > > 2 0.90 > > > > > > ie. *process to process* context switches are 3.4 times faster than signal > > > delivery. Ie. we can switch to a helper thread and back, and still be > > > faster than a *single* signal. Has someone gone through the lat_ctx.c and lat_sig.c code and convinced themselves these are measuring things which ought to be compared like this? When I wrote that code I didn't anticipate this comparison, so somebody should go look. I'd suggest that if you want to measure how fast you can communicate using signals versus pipes (or sockets or whatever), someone write up a test which has two processes bounce a token between each other using signals and then compare that with lat_pipe. It's not clear to me that you are comparing apples to apples. If someone does write the test, we'll add it to LMbench if it reveals anything useful. It should be easy enough to do. I can do it if it isn't obvious. -- --- Larry McVoy lm at bitmover.com http://www.bitmover.com/lm - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/