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Date: Tue, 08 Jul 2003 04:00:20 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: Dan Nelson <dnelson@allantgroup.com>
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cc: Andy Farkas <andyf@speednet.com.au>
Subject: Re: whats going on with the scheduler?
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Dan Nelson wrote:
> In the last episode (Jul 08), Andy Farkas said:
> > If setiathome is making lots of syscalls, then running the 3 instanses
> > should already show a problem, no?
> 
> Not if it's ssh that's holding Giant for longer than it should.   The
> setiathome processes may be calling some really fast syscall 500 times
> a second which doesn't cause a problem until ssh comes along and calls
> some other syscall that takes .1 ms to return but also locks Giant long
> enough to cause the other processes to all back up behind it.

Specifically, if it's sleeping with Giant held because the
Send-Q is full (use netstat to check) it could block things
for a long time, waiting for the queue to drain.

If this is the case, then you might want to ask Jeffrey Hsu
if it's safe to drop the lock during the sosend() (it probably
isn't).

-- Terry