X-Authentication-Warning: acp3bf.physik.rwth-aachen.de: broeker owned process doing -bs Date: Tue, 26 Sep 2000 11:26:00 +0200 (MET DST) From: Hans-Bernhard Broeker X-Sender: broeker AT acp3bf To: djgpp-workers AT delorie DOT com cc: ams AT ludd DOT luth DOT se Subject: Re: bnu2951b.zip's ar is slow In-Reply-To: <7458-Tue26Sep2000083937+0300-eliz@is.elta.co.il> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Reply-To: djgpp-workers AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: djgpp-workers AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk On Tue, 26 Sep 2000, Eli Zaretskii wrote: > > > How much memory does that 386 screamer have? Is it possible that the > > > large performance hit is due to paging because of the larger memory > > > required by bnu2951b, rather than to actually slower code? > > > > 4 MiB. That's a bit small. I take it you've taken the advice from the FAQ about configuring DOS and DJGPP for optimal performance, for this amount memory? > > I know that paging can make performance go out the window, but this is > > a little extreme; if it only was three or four times as slow or even > > ten, but ~65 times?! > > Paging can cause even 100-fold slow-down. Or even a thousand. Just as a rough comparson: data transfer rate to RAM: roughly 50 Megs/second data transfer rate to HD : roughly 0.5 Meg/second (for 386's) That already accounds for a factor of roughly a hundred. But we haven't mentioned the worst factor, yet: access latency of the HD : roughly 20 ms worst case: random access to the page file, for each 4KB paged out: --> 4kb every 20 ms (give or take another factor of two...) --> 0.200 Megs/s That's alreay a factor of 200 slower than main memory. Now imagine you have a PIII-800 or so, with a RAM access speed of O(1GB/s), to compete with, and that HD's haven't got more than about a factor of 2 better in latency, since the 386's time... > Does someone still have ld 2.8.1 installed to run a comparison? I think I still have it. What's the exact test case? Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de) Even if all the snow were burnt, ashes would remain.