From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1DYQUD-0004tJ-Fy for user-mode-linux-devel@lists.sourceforge.net; Wed, 18 May 2005 08:29:29 -0700 Received: from smtp003.mail.ukl.yahoo.com ([217.12.11.34]) by sc8-sf-mx1.sourceforge.net with smtp (Exim 4.41) id 1DYQUA-0002JD-Ca for user-mode-linux-devel@lists.sourceforge.net; Wed, 18 May 2005 08:29:29 -0700 From: Blaisorblade Subject: Re: [uml-devel] Explaination of system call function flow in TT mode References: <003e01c503b3$f3e46cb0$ac655e0a@sha.st.com> <20050518133331.GB3925@ccure.user-mode-linux.org> <428B5D30.6080706@fujitsu-siemens.com> In-Reply-To: <428B5D30.6080706@fujitsu-siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200505181728.48096.blaisorblade@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Wed, 18 May 2005 17:28:47 +0200 To: user-mode-linux-devel@lists.sourceforge.net Cc: Bodo Stroesser , Jeff Dike , Young Koh On Wednesday 18 May 2005 17:20, Bodo Stroesser wrote: > Jeff Dike wrote: > > On Wed, May 18, 2005 at 11:47:23AM +0200, Bodo Stroesser wrote: > >>I also thought about not saving FP-regs on each kernel entry. But if you > >> do this optimization, you need to save / restore FP-regs on switch_to. > >> Also you need to get the FP-regs when setting up a signal-handler > >> stackframe. And they > >>have to be restored on sys_(rt_)sigreturn from the values found in the > >>stackframe. > > > > True, but these are much less frequent than kernel entries/exits. > > Yes, so it makes sense to optimize this for i386 and x86_64. > > On s390, I'm not sure, what to do. Using s390's PTRACE_PEEK/POKEUSR_AREA > UML can read or write all regs including FP in a single ptrace call. > So, the change would speed up that call a bit, but would that be enough > to pay the cost of additional ptrace calls in switch_to or signal handling? I think no, because doing a syscall is probably more costly than copying some bytes, however it depends on the relative frequency. Doing a benchmark would probably be the better thing to do. -- Paolo Giarrusso, aka Blaisorblade Skype user "PaoloGiarrusso" Linux registered user n. 292729 http://www.user-mode-linux.org/~blaisorblade ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_id=7412&alloc_id=16344&op=click _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel