Alfred Perlstein wrote:
* [EMAIL PROTECTED] <[EMAIL PROTECTED]> [080430 18:13] wrote:
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?
Can you _really_ remove the locking? I don't think that would be safe
if the list is being manipulated, but I haven't checked.
Typically one uses a sentinal to get around such problems. Basically
insert a dummy object that no one should touch other than you, then
drop the lock periodically and insert it into the list, then resume.
net80211 uses a scan generation # to walk it's node lists. No sentinel.
Sam
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