Messages in this thread | | | Date | Sun, 24 Jun 2007 12:33:50 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] [RFC] Adjust queue unplugging and congestion limits |
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On Sun, 24 Jun 2007 19:27:23 +0200 Patrick Mau <mau@oscar.ping.de> wrote:
> Good afternoon > > Following is a small patch to "ll_rw_block" I played around with. > I started using "blktrace" to analyse the performance of my dated > LVM / MD / SCSI setup. It's really a nice tool, by the way. > > The changes are: > > * Change the "q->unplug_thresh" to be halve of "q->nr_requets". > This dynamically delays unplugging. It was hardcoded to 4 and > makes a difference in performace because of higher merge counts. > > * Change the unplug timeout to 10 milliseconds. > This is of course questionable, but I don't know why 3 was > choosen in the first place. I just played with it. > > * Set the congestion on/off limits further apart. > > * Cleanup the congestion checks (no "+1" anymore, more readable). > > * Update "q->unplug_thresh" whenever "q->nr_requests" is updated > through sysfs.
I don't think anyone has played with these settings since they first went in and yes, there may be some benefits available here.
> I did various artifical benchmarksi, mostly tar, dd and cp (also to NFS). > Comments are welcome.
umm, what was the result of this benchmarking? That is rather important information ;)
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