From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Kenneth W" Date: Tue, 07 Feb 2006 21:27:32 +0000 Subject: RE: [patch 3/6] prefetch bottom of kernel rbs stack at syscall exit path Message-Id: <200602072127.k17LRWg31633@unix-os.sc.intel.com> List-Id: References: <200601310913.k0V9DWg13193@unix-os.sc.intel.com> In-Reply-To: <200601310913.k0V9DWg13193@unix-os.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org David Mosberger-Tang wrote on Tuesday, February 07, 2006 1:19 PM > > Chen, Kenneth wrote on Tuesday, January 31, 2006 11:27 AM > > > David Mosberger-Tang wrote on Tuesday, January 31, 2006 9:45 AM > > > > How much latency does this add for a minimal syscall when > > > > everything is cached? > > > > > > I will get the measurement out shortly. > > > > Here are the numbers for break based getpid(): > > > > Vanilla 2.6.15: 238 cycles > > Vanilla + patches: 250 cycles > > Hmmh, 12 cycles lost. Can you see if you can do better? There really > are apps out there that care about this case (not getpid per se, but > minimal syscall entry/exit overhead when everything is cached). I'm with you completely on this. I'm not happy with it either. So back to the drawing board. - Ken