Messages in this thread | | | Date | Tue, 15 Jul 2003 07:43:04 +0200 | From | Jens Axboe <> | Subject | Re: RFC on io-stalls patch |
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On Mon, Jul 14 2003, Chris Mason wrote: > On Mon, 2003-07-14 at 18:45, Andrea Arcangeli wrote: > > On Mon, Jul 14, 2003 at 04:34:41PM -0400, Chris Mason wrote: > > > patch. It's a good starting point for the question "can we do better > > > for reads?" (clearly the answer is yes). > > > > Jens's patch will block every writers until the parallel sync readers go > > away. if we add a 5 seconds delay for every write, sure readers will > > run faster too in contest, and in turn it's not obvious to me it's > > necessairly a good starting point. > > For real server workloads I agree the patch isn't a good idea. But > Jens' workload had a small number of kernel compilers (was it one proc > or make -j4 or so?), so clearly the writers could still make progress. > This doesn't mean I want the patch but it does mean the numbers are > worth thinking about ;-) > > If we go back to Jens' numbers: > > ctar_load: > Kernel [runs] Time CPU% Loads LCPU% Ratio > 2.4.22-pre5 3 235 114.0 25.0 22.1 1.75 > 2.4.22-pre5-axboe 3 194 138.1 19.7 20.6 1.46 > ^^^^^^ > The loads column is the number of times ctar_load managed to run during > the kernel compile, and the patched kernel loses each time. This must > partially be caused by the lower run time overall, but it is still > important data. It would be better if contest gave us some kind of > throughput numbers (avg load time or something).
Well, look at the ratio given the run times listed. You'll see that they are extremely close (0.1064 for 2.4.22-pre5 vs 0.1015 for 2.4.22-pre5-axboe).
It just shows that we are not hitting the possible bad problems in these work loads.
-- Jens Axboe
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