[darcs-devel] [issue1202] darcs whatsnew significantly slower on a hashed repository

[Simon Marlow]

New submission from Simon Marlow <simonmar at microsoft.com>:

As requested by Eric, I'm submitting a new ticket on this.  Note this slowdown is *not* caused by the GHC 6.8.2 getSymbolicLinkStatus bug.

2.0.2 (+ 326 patches)
> darcs +RTS --info
 [("GHC RTS", "Yes")
 ,("GHC version", "6.8.3")
 ,("RTS way", "rts_thr")
 ,("Host platform", "x86_64-unknown-linux")
 ,("Build platform", "x86_64-unknown-linux")
 ,("Target platform", "x86_64-unknown-linux")
 ,("Compiler unregisterised", "NO")
 ,("Tables next to code", "YES")
 ]

With a fresh GHC testsuite repository (using darcs get --hashed http://darcs.haskell.org/testsuite):

~/darcs/testsuite > time darcs w -s
No changes!
16.48s real   9.64s user   5.18s system   89% darcs w -s
~/darcs/testsuite > time darcs w -s
No changes!
14.98s real   8.92s user   4.16s system   87% darcs w -s

ok, so that was on an NFS filesystem, so let's try locally:

/tmp > cp -r ~/darcs/testsuite .
/tmp > cd testsuite
/tmp/testsuite > time darcs w -s
No changes!
9.43s real   9.40s user   4.39s system   146% darcs w -s
/tmp/testsuite > time darcs w -s
No changes!
9.14s real   8.96s user   3.84s system   140% darcs w -s

And with an old darcs1 repository, again on NFS:

~/darcs/ghc-testing/testsuite > time darcs w -s
4.20s real   0.24s user   0.34s system   13% darcs w -s
~/darcs/ghc-testing/testsuite > time darcs w -s
2.38s real   0.22s user   0.39s system   25% darcs w -s

Fortunately the darcs-2 format is much better:

~/darcs/testsuite_0 > time darcs w -s
No changes!
3.79s real   1.17s user   0.79s system   51% darcs w -s
~/darcs/testsuite_0 > time darcs w -s
No changes!
2.65s real   1.13s user   0.70s system   69% darcs w -s
~/darcs/testsuite_0 > time darcs w -s
No changes!
1.67s real   1.11s user   0.74s system   110% darcs w -s

So I'm not sure how much you should care about this bug, since it only affects the transitional hashed format.  Still, it will probably prevent me from using the hashed format for the GHC repos.

Cheers,
        Simon

----------
messages: 6590
nosy: dagit, dmitry.kurochkin, kowey, simon, simonmar, thorkilnaur
status: unread
title: darcs whatsnew significantly slower on a hashed repository

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Darcs bug tracker <bugs at darcs.net>
<http://bugs.darcs.net/issue1202>
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