From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Received: (qmail 22929 invoked from network); 10 Jan 2003 22:55:59 -0000 Received: from unknown (HELO localhost.redhat.com) (216.138.202.10) by 209.249.29.67 with SMTP; 10 Jan 2003 22:55:59 -0000 Received: from redhat.com (localhost [127.0.0.1]) by localhost.redhat.com (Postfix) with ESMTP id C80AF3E02; Fri, 10 Jan 2003 17:55:48 -0500 (EST) Message-ID: <3E1F4F74.5020704@redhat.com> Date: Fri, 10 Jan 2003 22:55:00 -0000 From: Andrew Cagney User-Agent: Mozilla/5.0 (X11; U; NetBSD macppc; en-US; rv:1.0.1) Gecko/20021211 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Daniel Jacobowitz Cc: gdb@sources.redhat.com Subject: Re: Known problems with dcache? References: <3E1F46CB.9060104@redhat.com> <20030110222551.GA10139@nevyn.them.org> <3E1F4ACC.7080504@redhat.com> <20030110223834.GA10769@nevyn.them.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2003-01/txt/msg00182.txt.bz2 > On Fri, Jan 10, 2003 at 05:35:56PM -0500, Andrew Cagney wrote: > >> > >> >We don't use the straw on some targets now; Linux (need to get back to >> >that patch and turn it on always!), *BSD. > >> >> Right so that 32 byte read is now cheap. >> > >> >The dcache needs some serious work if you want it to be always on. >> >Last time I tested it it caused an actual slowdown. Basically, it's >> >too small to be useful. >> > >> >#define DCACHE_SIZE 64 >> >#define LINE_SIZE_POWER (5) >> > >> >So it never stores more than 2K. LinuxThreads _overwhelms_ that, by a >> >downright boggling amount. > >> >> You wouldn't know why it caused a slow down? Th 32 byte read should now >> be cheaper. > > > This was before the 32-byte-read support. So we read lines in, did > more computation than before, and overwrote them in the cache; exactly > the same I/O, more CPU. Well, possibly more I/O. And, I think, the I/O / context switch / ... is the expensive part. > Might be worth trying it again, with larger > lines, now. Not sure. Was it on an i386? If it was, the other other cache would easily skew any results. Andrew