Messages in this thread | | | Date | Mon, 21 May 2007 19:04:09 +0200 | From | Jens Axboe <> | Subject | Re: CFQ IO scheduler patch series - AIM7 DBase results on a 16-way IA64 |
| |
On Mon, May 21 2007, Alan D. Brunelle wrote: > Jens Axboe wrote: > >On Mon, May 21 2007, Alan D. Brunelle wrote: > > > >>Jens Axboe wrote: > >> > >>>On Tue, May 01 2007, Alan D. Brunelle wrote: > >>> > >>> > >>>>Jens Axboe wrote: > >>>> > >>>> > >>>>>On Mon, Apr 30 2007, Alan D. Brunelle wrote: > >>>>> > >>>>> > >>>>>>The results from a single run of an AIM7 DBase load on a 16-way ia64 > >>>>>>box (64GB RAM + 144 FC disks) showed a slight regression (~0.5%) by > >>>>>>adding in this patch. (Graph can be found at > >>>>>>http://free.linux.hp.com/~adb/cfq/cfq_dbase.png ) It is only a > >>>>>>single set of runs, on a single platform, but it is something to keep > >>>>>>an eye on as the regression showed itself across the complete run. > >>>>>> > >>>>>> > >>>>>Do you know if this regression is due to worse IO performance, or > >>>>>increased system CPU usage? > >>>>> > >>>>> > >>>>We performed two point runs yesterday (20,000 and 50,000 tasks) and > >>>>here are the results: > >>>> > >>>>Kernel Tasks Jobs per Minute %sys (avg) > >>>>------ ----- --------------- ---------- > >>>>2.6.21 20000 60,831.1 39.83% > >>>>CFQ br 20000 60,237.4 40.80% > >>>> -0.98% +2.44% > >>>> > >>>>2.6.21 50000 60,881.6 40.43% > >>>>CFQ br 50000 60,400.6 40.80% > >>>> -0.79% +0.92% > >>>> > >>>>So we're seeing a slight IO performance regression with a slight > >>>>increase in %system with the CFQ branch. (A chart of the complete run > >>>>values is up on http://free.linux.hp.com/~adb/cfq/cfq_20k50k.png ). > >>>> > >>>> > >>>Alan, can you repeat that same run with this patch applied? It > >>>reinstates the cfq lookup hash, which could account for increased system > >>>utilization. > >>> > >>> > >>Hi Jens - > >> > >>This test was performed over the weekend, results are updated on > >> > >>http://free.linux.hp.com/~adb/cfq/cfq_dbase.png > >> > > > >Thanks a lot, Alan! So the cfq hash does indeed improve things a little, > >that's a shame. I guess I'll just reinstate the hash lookup. > > > > > You're welcome Jens, but remember: It's one set of data; from one > benchmark; on one architecture; on one platform...don't know if you > should scrap the whole thing for that! :-) At the very least, I could > look into trying it out on another architecture. Let me see what I can > dig up...
Of course it would be great if you could test on something else as well, but I was aware that the cfq hash lookup could potentially cause a performance degradation with some workloads. Your test shows about a 0.3% drop, which isn't a lot but still looks consistent. The cfq hash code wasn't that complicated, so if it helps a bit, then I'm inclined to put it back in.
Let me know if you can run it on something else!
-- Jens Axboe
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |