Odd performance problem (hitching)

Don Lewis truckman at FreeBSD.org
Wed Aug 31 01:55:14 GMT 2005

On 31 Aug, Daniel O'Connor wrote:
> On Tuesday 30 August 2005 17:50, Daniel O'Connor wrote:
>> > You might try significantly decreasing MAXVNODES_MAX in
>> > sys/kern/vfs_subr.c and rebuilding your kernel.
>> OK..
>> I'll try timing when the drop outs happen :)
> Hmm they appear to be every 10 seconds on the dot.

Hmn, I wonder what runs every 10 seconds ...

> I haven't changed any syncer delay stuff either..
> kern.filedelay: 30
> kern.dirdelay: 29
> kern.metadelay: 28

Those won't make any difference.  They govern how many slots behind in
the worklist that items of various types get inserted.  The syncer wakes
up once per second, processes all the items in a worklist slot, then
goes back to sleep.  The syncer vnode for each file system gets inserted
when the file system is mounted and stays in the same slot, so the ugly
FOREACH loop I mentioned earlier gets executed once each time the entire
worklist is scanned, and since the worklist has 32 slots, the problem
should only occur once every 32 seconds if you have one file system that
has hogged most of the vnodes.  If there are multiple file systems, the
syncer vnodes will inserted at various power of two locations in the
list, but I don't see a way to get activity spaced at ten second

> Still using SCHED_4BSD too.

More information about the freebsd-current mailing list