Re: ps performance sucks (was Re: dcache_rcu [performance results])

[Martin J. Bligh]

>> The locking of walking the tasklist seems non-trivial, but we may well
>> end up with something like that. By the time you finish, it looks more
>> like a /dev device thing than /proc (which I'm fine with), and looks
> 
> Can people just oprofile this instead of guessing? Opening a file is not
> very expensive anymore, so if ps is noticeably slow, it must be something
> else.
> 
> 'To measure is to know'

Errm... we have profiled it. Look at the subject line ... this started
off as a dcache_rcu discussion. The dcache lookup ain't cheap, for 
starters, but that's not really the problem ... it's O(number of tasks),
which sucks.

M.