haskell/cabal — pull request #1614 by trofi (2013-12-13 21:00:58+00:00)
Title: cabal upload: use ByteString instead of String

The difference is seen nicely on Raincat package (9MB tarball):
$ /usr/bin/time cabal upload --check Raincat-1.1.1.3.tar.gz
39.92user
0.38system
4:02.50elapsed
16%CPU (0avgtext+0avgdata 1855712maxresident)k

Insane amounts of used RAM (1.8GB) seem to stem from 'String'
inefficiency especially on 64-bit platforms where overhead is
about 16 times:

- 97% of CPU time is taken by GC scans (according to +RTS -sstderr)
- 9MB tarball would take ~150MBs of RAM, 100MB tarball would...

Attempt to pack them into HTTP headers leads to further growth.

The patch only changes underlying structure to ByteString.Lazy.Char8:
$ /usr/bin/time patched-cabal upload --check Raincat-1.1.1.3.tar.gz

0.25user
0.16system
4:28.61elapsed
0%CPU (0avgtext+0avgdata 66864maxresident)k

In short: 1.8GB -> 66MB RAM reduction + 16% -> 0% CPU usage.

Reported-by: "Mikhail S. Pobolovets"
Signed-off-by: Sergei Trofimovich