Messages in this thread | | | Date | Fri, 7 May 1999 20:59:20 -0700 | From | "David S. Miller" <> | Subject | Re: Overscheduling DOES happen with high web server load. |
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From: Andi Kleen <ak@muc.de> Date: Fri, 7 May 1999 20:24:39 +0200
It was shown earlier in the thread that no thundering herd occured in the test, because apache serializes the accept with a lock.
There is no global consensus of this fact. Apache may be using flock to serialize, but nobody has stated that flock does not present the same problem on the kernel side (everyone waking up and fighting for the flock, one winning and everyone else going back to sleep).
The scheduling rate is absurd, and so are the run queue lengths which must be leading to this behavior. I am willing to be proven otherwise, but my reading of the data is still galloping herd.
Someone could put this to rest by implementing a quick profiling hack in the kernel, do something similar to what the timer based profiling in the kernel does already, but instead record profiling ticks for calls to the scheduler and record the tick for who it is that called the scheduler (essentially you're profiling the WCHAN).
Data produced from this during one of these tests would prove extremely useful.
Later, David S. Miller davem@redhat.com
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