On Mon, 2009-04-06 at 17:01 -0500, Steven Pratt wrote: > I am continuing to do runs to provide more data on the random write > issues with btrfs. I have just posted 2 sets of runs here: > http://btrfs.boxacle.net/repository/raid/longrun/ > > these are on a pull of the btrfs-unstable experimental branch from 4/3. > > These are 100 minute runs of the 128 thread random write workload on the > raid system (1 for btrfs and 1 for ext3). Included in these runs are > graphs of all the iostat, sar and mpstat data (see analysis directories). > > A couple of interesting things. First, we see the choppiness of the IO > in btrfs compared to ext3. > http://btrfs.boxacle.net/repository/raid/longrun/btrfs-longrun/btrfs1.ffsb.random_writes__threads_0128.09-04-06_10.25.03/analysis/iostat-processed.001/chart.html > > http://btrfs.boxacle.net/repository/raid/longrun/ext3-longrun/btrfs1.ffsb.random_writes__threads_0128.09-04-06_13.44.49/analysis/iostat-processed.001/chart.html > > > In particular look at graphs 7 and 11 which show write iops and > throughput. Ext3 is nice and smooth, while btrfs has a repeating > pattern of dips and spikes, with IO going to 0 on a regular basis. > The dips and spikes may be from the allocator. Basically what happens is after each commit we end up with a bunch of small blocks available for filling again. Could you please try with -o ssd? > Another interesting observation is what looks a lot like a memory leak. > Looking at chart 6 Memory at : > http://btrfs.boxacle.net/repository/raid/longrun/btrfs-longrun/btrfs1.ffsb.random_writes__threads_0128.09-04-06_10.25.03/analysis/sar-processed.001/chart.html > > we see that the amount of page cache drops slowly throughout the entire > run. Starting up around 3.5GB and dropping to about 2.3GB by the end of > the run. The memory seems to have moved to the slab which grew to > 1.5GB. Doing a repeat of the run while watching slabtop, we see that > size-2048 is responsible for the majority of the slab usage (over 1GB). > size-2048? That's probably the csums. I'll give it a shot when I get back next week. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
