Date: Sat, 6 Mar 2004 18:50:13 -0500 (EST) From: Robert Watson <rwatson@FreeBSD.org> To: current@FreeBSD.org Subject: Giant and timeouts and more timeouts, and more timeouts... and NFS. Message-ID: <Pine.NEB.3.96L.1040306184054.77813M-100000@fledge.watson.org>
next in thread | raw e-mail | index | archive | help
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@fledge.watson.org Senior Research Scientist, McAfee Research
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.NEB.3.96L.1040306184054.77813M-100000>