Firefox memory usage & cgroups

Ahojte, mojim cielom je obmedzit firefox v pouziti RAM-ky. Pouzivam cgroups, len rovno bez akychkolvek pomocnych prikazov, teda napr takto. Mam VirtualBox, 512 MB RAM, 512 MB swap.

Spustim firefox, jeho PID zapisem do prislusnej grupy: 
cat "PID" > /sys/fs/cgroup/all/firefox/tasks

Nastavim memory limit:
echo 150M > memory.limit_in_bytes

#cat memory.memsw.limit_in_bytes
9223372036854775807

Vsetko funguje, firefox zacne swapovat. Otvaram vela, vela, vela tabov. Po chvili uz firefox zamrzne. iotop ukazuje jedinu aktivitu, firefox konstantne nacitava asi 13 MB/sek, bez akehokolvek zapisu. Nechapem, ze co robi, co stale nacitava, ved za 30 sekund tymto tempom musi nacitat 300 MB, to mu musi stacit.

Pokial vsak zrazu nastavim 200M:
echo 200M > memory.limit_in_bytes

Tak firefox sa zazracne rozbehne (vybehne par dialogov "unresponsive script wait/cancel") a potom pokracuje dalej. Nerozumiem preco firefox/kernel nezoswapuje stranky, ktore sa nepouzivaju (urcite je ich vela) a neuvolni tak pamat.
Vdaka za napady a citanie. :-)


#cat /sys/fs/cgroup/all/firefox/memory.stat 

cache 1150976
rss 155906048
mapped_file 618496
pgpgin 24078180
pgpgout 24039836
swap 41340928
pgfault 4665460
pgmajfault 993852
inactive_anon 78061568
active_anon 77844480
inactive_file 606208
active_file 544768
unevictable 0
hierarchical_memory_limit 157286400
hierarchical_memsw_limit 9223372036854775807
total_cache 1150976
total_rss 155906048
total_mapped_file 618496
total_pgpgin 24078180
total_pgpgout 24039836
total_swap 41340928
total_pgfault 4665460
total_pgmajfault 993852
total_inactive_anon 78061568
total_active_anon 77844480
total_inactive_file 606208
total_active_file 544768
total_unevictable 0

# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 12.04.2 LTS
Release:	12.04
Codename:	precise

# uname -a
Linux my-virtual 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:41:14 UTC 2012 i686 i686 i386 GNU/Linux

Dotaz: Firefox memory usage & cgroups