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SubjectRe: Strange performance behavior of 2.4.0-test9
kumon@flab.fujitsu.co.jp writes:
> Rik van Riel writes:
> > On Wed, 25 Oct 2000 kumon@flab.fujitsu.co.jp wrote:
> > > I found very odd performance behavior of 2.4.0-test9 on a large SMP
> > > server, and I want some clues to investigate it.
> > >
> > > 1) At the 8 cpu configuration, test9 shows extremely inferior
> > > performance.
> > > 2) on test8, 8-cpu configuration shows about 2/3 performance of 4-cpu.
> > ^^^^^ test9 ??

IMHO, the modification of file-system code causes the weird
performance.

Most of processes are slept at:
posix_lock_file()->locks_block_on()->interruptible_sleep_on_locks()

We revert two of test9 files (fs/fcntl.c fs/flock.c), to the previous
version, the performance problem disappeared and it becomes to the
same level as test8.

To narrow the problem, we measured performance of 3 configuration:
1) test9 with test8 fs/fcntl.c, test8 fs/flock.c
2) test9 with test8 fs/fcntl.c
3) test9 with test8 fs/flock.c

Only 3) shows the problem, so the main problem reside in fcntl.c (not
in flock.c).

So it seems:
the web-server, apache-1.3.9 in the redhat-6.1, issues lots of fcntl
to the file and those fcntls collide each other, and the processes
are blocked.


What has happend to fcntl.c?

--
Computer Systems Laboratory, Fujitsu Labs.
kumon@flab.fujitsu.co.jp
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