Messages in this thread | | | Date | Sun, 29 Aug 1999 14:48:20 -0600 | From | yodaiken@chelm ... | Subject | Re: [rtl] Low-latency patches working GREAT (<2.9ms audio latency), see testresults ,but ISDN troubles |
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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?
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