Re: Giant and timeouts and more timeouts, and more timeouts... and NFS.

Sorry, the below sample was '10 seconds', so divide all numbers by 10 for
a per-second count.  300 timeouts a second for NFS, 25 for scrn_timer,
etc.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Senior Research Scientist, McAfee Research

On Sat, 6 Mar 2004, Robert Watson wrote:

> 
> I was playing a bit with mutex profiling this weekend, measuring mutex use
> on the netperf_socket branch (which has the IPv4 and socket code running
> Giant-free).  I was a bit surprised to find a massive number of
> timeout/callouts that require Giant running every second.  I added a
> little instrumentation to see just how much Giant was getting used, and
> found the following in a short sample (1 second) on an idle system: 
> 
>   none:/tmp> sysctl debug.to_gsample_reset=1 ; sleep 10 ; sysctl
>     debug.to_gsample > /tmp/sample ; wc /tmp/sample
>   debug.to_gsample_reset: 0 -> 0
> 
>   paprika:/tmp> ./process.pl | ./count.pl | sort -nr
>   uhci_poll_hub: 41
>   scrn_timer: 253
>   rpcclnt_timer: 1007
>   nfsrv_timer: 1007
>   nfs_timer: 1007
>   nd6_timer: 10
>   loadav: 1
>   in6_rr_timer: 2
>   if_slowtimo: 10
>   dasendorderedtag: 1
>   comwakeup: 10
> 
> So that's 3000 timeouts a second for the NFS server and client code (even
> though neither is used on this machine), each one of which will grab and
> release Giant.  That seems a little gratuitous to me...
> 
> Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
> robert_at_fledge.watson.org      Senior Research Scientist, McAfee Research
> 
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