From mboxrd@z Thu Jan 1 00:00:00 1970 From: yodaiken@chelm.cs.nmt.edu Date: Sun, 29 Aug 1999 20:48:20 +0000 Subject: Re: [rtl] Low-latency patches working GREAT (<2.9ms audio latency), see testresults ,but ISDN troubl Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org On Sun, Aug 29, 1999 at 09:15:19AM +0200, Ingo Molnar wrote: > > On Sat, 28 Aug 1999 yodaiken@fsmlabs.com wrote: > > > I'm concerned that the major improvement has come from additional > > calls to schedule instead of from some basic improvements in algorithm. > > there are _no_ extra calls to schedule, only if necessery. Zero, nil, > nada. Please check out the patch. Tell me what I misunderstood. As far as I can tell, pre patch behavior involves many fewer calls to schedule, post patch behavior for a write, for example, can make at least one extra call to the scheduler for every block copied. If "needs_resched >0" it is still not necessarily true that the call to the scheduler is "necessary". Consider, a long running data base program is writing backing store out to disk. Old behavior: the write absorbs as much free memory as possible to optimize disk behavior. New behavior: a screen saver, which is small i/o bound, causes needs resched to be set continually, and the write is segmented into many smaller writes. We now have, like NT, optimized the screen saver on a server while hammering file system performance. Isn't that correct?