Date: Wed, 30 Apr 2008 18:13:34 -0700 From: gnn@freebsd.org To: stable@freebsd.org Subject: Some odd behaviour of vmstat and vmtotal... Message-ID: <m2lk2ultc1.wl%gnn@neville-neil.com>
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Howdy, In deploying 7.0 at work we were finding a persistent problem when running "vmstat 1" on systems. The problem shows up as a 10ms "pause" in processing, usually packet stamping and forwarding by a user level process. This is due to the fact that vmstat calls the vmtotal() routine which in turn does a whole lot of locking. The vmtotal call locks and walks the VM object list twice in a mark and sweep operation. So, the question is, "What is the right way to fix this?" I could remove the locking since the O_ACTIVE bit is not used by any other routine besides vmtotal, but I'm not too happy about that. The relevant code can be found in src/sys/vm/vm_meter.c in vmtotal(). Thoughts? Best, George
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