Re: [patch 0/3] j_state_lock, j_list_lock, remove-bitlocks

Ingo Molnar
2005-03-16T10:30:22Z

* Andrew Morton <akpm@osdl.org> wrote:

> I forget how much of the 1000% came from that, but it was quite a lot.
>
> Removing the BKL was the first step. That took the context switch
> rate under high load from ~10,000/sec up to ~300,000/sec. Because the
> first thing a CPU hit on entry to the fs was then a semaphore.
> Performance rather took a dive.
>
> Of course the locks also became much finer-grained, so the contention
> opportunities lessened. But j_list_lock and j_state_lock have fs-wide
> scope, so I'd expect the context switch rate to go up quite a lot
> again.
>
> The hold times are short, and a context switch hurts rather ore than a
> quick spin.

which particular workload was this - dbench? (I can try PREEMPT_RT on an
8-way, such effects will show up tenfold.)

Ingo