Re: [PATCH] Clustering indirect blocks in Ext3

["Abhishek Rai" <abhishekrai@google.com>]

Thanks for the suggestion Matt.

It took me some time to get compilebench working due to the known
issue with drop_caches due to circular lock dependency between
j_list_lock and inode_lock (compilebench triggers drop_caches quite
frequently). Here are the results for compilebench run with options
"-i 30 -r 30". I repeated the test 5 times on each of vanilla and mc
configurations.

Setup: 4 cpu, 8GB RAM, 400GB disk.

Average vanilla results
==========================================================================
intial create total runs 30 avg 46.49 MB/s (user 1.12s sys 2.25s)
create total runs 5 avg 12.90 MB/s (user 1.08s sys 1.97s)
patch total runs 4 avg 8.70 MB/s (user 0.60s sys 2.31s)
compile total runs 7 avg 21.44 MB/s (user 0.32s sys 2.95s)
clean total runs 4 avg 59.91 MB/s (user 0.05s sys 0.26s)
read tree total runs 2 avg 21.85 MB/s (user 1.12s sys 2.89s)
read compiled tree total runs 1 avg 23.47 MB/s (user 1.45s sys 4.89s)
delete tree total runs 2 avg 13.18 seconds (user 0.64s sys 1.02s)
no runs for delete compiled tree
stat tree total runs 4 avg 4.76 seconds (user 0.70s sys 0.50s)
stat compiled tree total runs 1 avg 7.84 seconds (user 0.74s sys 0.54s)

Average metaclustering results
==========================================================================
intial create total runs 30 avg 45.04 MB/s (user 1.13s sys 2.42s)
create total runs 5 avg 15.64 MB/s (user 1.08s sys 1.98s)
patch total runs 4 avg 10.50 MB/s (user 0.61s sys 3.11s)
compile total runs 7 avg 28.07 MB/s (user 0.33s sys 4.06s)
clean total runs 4 avg 83.27 MB/s (user 0.04s sys 0.27s)
read tree total runs 2 avg 21.17 MB/s (user 1.15s sys 2.91s)
read compiled tree total runs 1 avg 22.79 MB/s (user 1.38s sys 4.89s)
delete tree total runs 2 avg 9.23 seconds (user 0.62s sys 1.01s)
no runs for delete compiled tree
stat tree total runs 4 avg 4.72 seconds (user 0.71s sys 0.50s)
stat compiled tree total runs 1 avg 6.50 seconds (user 0.79s sys 0.53s)

Overall, metaclustering does better than vanilla except in a few cases.

Thanks,
Abhishek

On Nov 15, 2007 11:37 PM, Matt Mackall <mpm@selenic.com> wrote:
> On Thu, Nov 15, 2007 at 11:02:19PM -0800, Andrew Morton wrote:
> > On Thu, 15 Nov 2007 21:02:46 -0800 "Abhishek Rai" <abhishekrai@google.com> wrote:
> ...
> > > 3. e2fsck speedup with metaclustering varies from disk
> > > to disk with most benefit coming from disks which have a large number
> > > of indirect blocks. For disks which have few indirect blocks, fsck
> > > usually doesn't take too long anyway and hence it's OK not to deliver
> > > a huge speedup there. But in all cases, metaclustering doesn't cause
> > > any degradation in IO performance as seen in the benchmarks above.
> >
> > Less speedup, for more-and-smaller files, it appears.
> >
> > An important question is: how does it stand up over time?  Simply laying
> > files out a single time on a fresh fs is the easy case.  But what happens
> > if that disk has been in continuous create/delete/truncate/append usage for
> > six months?
>
> Try Chris Mason's compilebench, which is a decent aging simulation.
>
> --
> Mathematics is the supreme nostalgia of our time.
>
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