Re: spinlock usage - ext2_get_block, lru_list_lock

[torvalds@transmeta.com (Linus Torvalds)]

In article <20010321180607.A11941@linuxcare.com>,
Anton Blanchard  <anton@linuxcare.com.au> wrote:
>
>It was not surprising the BKL was one of the main offenders. Looking at the
>stats ext2_get_block was the bad guy (UTIL is % of time lock was busy for,
>WAIT is time spent waiting for lock):

Actually, I find the BKL fairly surprising - we've whittled down all the
major non-lowlevel-FS offenders, and I didn't realize that it's still
there in do_exit().

And the do_exit() case should be _trivial_ to fix: almost none of the
code protected by the kernel lock in the exit path actually needs the
lock. I suspect you could cut down the kernel lock there to much
smaller.

The big case seems to be ext2_get_block(), we'll fix that early in
2.5.x. I think Al already has patches for it.

As to lseek, that one should probably get the inode semaphore, not the
kernel lock. 

		Linus