Interesting analysis of linux kernel threading by IBM

[David S. Miller]

   Date:   Fri, 21 Jan 2000 23:18:51 +0000 (GMT)
   From: Alan Cox <alan en lxorguk.ukuu.org.uk>

   > When I run SPECWeb96 tests here, I see both a large number of running
   > process and a huge number of context switches. 

Running 2.2.x I imagine as well, right?

   Specweb96 is about as relevant to real world web performance as the colour
   of car you own. And in this case massively so. Run your test with thttpd.
   Your run queue length will be _one_. Always one, never more and under load
   never less. Its an architectural issue in your web server.

Only partly true Alan, only 2.3.x has the "dumb wakeups" issue with
TCP accept fixed (2.2.x will cause ~3 wakeups for each new connection
when only 1 should be made).  That plays a big factor as well,
remember the same exact thread about all of this "run queue
scalability" bogosity we had nearly a year ago?

So to the original specweb96 tester, divide your context switch number
by 3, does it look more sane now? :-)

However Alan is right, web server architecture has a lot to do with
bad "benchmark" performance.

Later,
David S. Miller
davem en redhat.com

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