From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3851 invoked by alias); 23 Jun 2003 03:57:13 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 2085 invoked from network); 23 Jun 2003 03:56:29 -0000 Received: from unknown (HELO crack.them.org) (146.82.138.56) by sources.redhat.com with SMTP; 23 Jun 2003 03:56:29 -0000 Received: from dsl093-172-017.pit1.dsl.speakeasy.net ([66.93.172.17] helo=nevyn.them.org ident=mail) by crack.them.org with asmtp (Exim 3.12 #1 (Debian)) id 19UISG-0003T4-00; Sun, 22 Jun 2003 22:57:20 -0500 Received: from drow by nevyn.them.org with local (Exim 3.36 #1 (Debian)) id 19UIRN-0004yn-00; Sun, 22 Jun 2003 23:56:25 -0400 Date: Mon, 23 Jun 2003 03:57:00 -0000 From: Daniel Jacobowitz To: Andrew Cagney Cc: gdb@sources.redhat.com Subject: Re: Always cache memory and registers Message-ID: <20030623035625.GA19125@nevyn.them.org> Mail-Followup-To: Andrew Cagney , gdb@sources.redhat.com References: <3EF62D05.8070205@redhat.com> <20030622223412.GA15860@nevyn.them.org> <3EF633B8.4030009@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3EF633B8.4030009@redhat.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2003-06/txt/msg00442.txt.bz2 On Sun, Jun 22, 2003 at 06:54:48PM -0400, Andrew Cagney wrote: > > >>The only proviso being that the the current cache and target vector > >>would need to be modified so that the cache only ever requested the data > >>needed, leaving it to the target to supply more if available (much like > >>registers do today). The current dcache doesn't do this, it instead > >>pads out small reads :-( > > > > > >It needs tweaking for other reasons too. It should probably have a > >much higher threshold before it starts throwing out data, for one > >thing. > > > >Padding out small reads isn't such a bad idea. It generally seems to > >be the latency that's a real problem, esp. for remote targets. I think > >both NetBSD and GNU/Linux do fast bulk reads native now? I'd almost > >want to increase the padding. > > No, other way. > > Having GDB pad out small reads can be a disaster - read one too many > bytes and ``foomp''. This is one of the reasons why the dcache was > never enabled. What do you mean? I would have thought this was the responsibility of the stub to manage... > However, it is totally reasonable for the target (not GDB) to supply > megabytes of memory mapped data when GDB only asked for a single byte! > The key point is that it is the target that makes any padding / transfer > decisions, and not core GDB. If the remote target fetches too much data > and `foomp' then, hey not our fault, we didn't tell it to read that > address :-^ Oh, I see what you're getting at. Hmm, this would require fudging the interfaces a bit, in order for the target to return excess memory. It could be done. Hm.... -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer