Re: nice really nice?

[thomas <tom at huno dot net>]

Robert Collins <rbcollins@cygwin.com> wrote:
> On Wed, 2002-11-27 at 00:25, thomas wrote:

>> SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS)
>> SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL)

> If you do that, expect to get a hung system real fast.

cdrecord does exactly the above during writing; cdrdao sets itself to
HIGHEST (also using realtime class). And windows task manager also
reports it is running at realtime.

> What happens with nice -20 ?

There is no difference from 0 - 20, and none between -1 and -20.

>> $ time cat test.iso | nice --1 dd of=/dev/null
>> real    1m51.428s
>> user    0m0.107s
>> sys     0m0.015s

> Ah, I see it now, you expect a higher priority, and get less
> performance.

Less performance means by the factor of about 15 here.

> What happens if you do this:
> time nice --1 cat test.iso | nice --1 dd of=/dev/null ?

Well first of all it steals all my ressources :) Winamp stops to play on
my XP2000+.

$ time nice --1 cat test.iso | nice --1 dd of=/dev/null
real    0m6.784s

and while i was at it i did:

$ time nice --1 cat test.iso | dd of=/dev/null
real    0m7.470s

> sched.cc It was introduced around 1.1 IIRC.

I don't know if you read one of my other two threads on this issue, but
to save you some reading a very quick summary:

I have cdrecord binaries compiled with cygwin 1.1.18 (running with
cygwin1.dll 1.1.8 of course) and they work perfectly. When i compile the
very same cdrecord sources with 1.3.x (+ dll) i get the phenomen you saw
in the tests. Also this behaviour only shows when pipes are involved,
when i read the iso in directly it works great.


I'm just trying to find out what happened on the way. So if you have any
idea what might be causing this behaviour i'd greatly appreciate it,
you'd save me some of the hours i will spend digging in CVS :)

thomas


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