On Mon, 17 Oct 2005, Linus Torvalds wrote:
> On Mon, 17 Oct 2005, Eric Dumazet wrote:
> >
> > What about call_rcu_bh() which I left unchanged ? At least one of my
> > production machine cannot live very long unless I have maxbatch = 300, because
> > of an insane large tcp route cache (and one of its CPU almost filled by
> > softirq NIC processing)
>
> I think we'll have to release 2.6.14 with maxbatch at the high value
> (10000).
Btw, I'm going to apply your patch in _addition_ to the bigger maxbatch
value.
It might help latency a bit, but more importantly, on one of my machines
(but only one - it probably depends on how much memory you have etc), I
can re-create the out-of-file-descriptors thing even with a maxbatch of a
million.
Probably what happens is that the rcu callbacks just grow fast enough
without any quiescent period that the maxbatch thing just never matters:
we simply run out of file descriptors because we haven't even gotten
around to trying to free them yet.
I'm compiling with your patch on that machine to verify that it does
actually help keep the queues down. Just doing a
while : ; do cat /proc/slabinfo | grep filp; sleep 1; done
while running the test programs gives some alarming numbers as-is.
Your patch keeps the numbers _much_ more stable.
Regardless, keeping track of the number of rcu callback events we have
will almost inevitably be part of whatever future strategy we take, so
your patch is definitely a step in the right direction, even if we have to
tweak it later.
Linus
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