Giant and timeouts and more timeouts, and more timeouts... and
NFS.
Robert Watson
rwatson at FreeBSD.org
Sat Mar 6 15:53:19 PST 2004
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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