On Mon, Jul 06, 2009 at 03:47:39PM -0400, Josef Bacik wrote:
> This isn't a huge deal, but using a big beefy box with more CPUs than what is
> sane, you can get a nice flood of softlockup messages when running heavy
> multi-threaded io tests on ext2/3. The processors compete for blocks from the
> allocator, so they will loop quite a bit trying to get their allocation. This
> patch simply makes sure that we reschedule if need be. This made the softlockup
> messages disappear whereas before they happened almost immediately. Thanks,
>
> Tested-by: Evan McNabb <emcnabb@xxxxxxxxxx>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> fs/ext2/balloc.c | 1 +
> fs/ext3/balloc.c | 2 ++
> 2 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 7f8d2e5..17dd55f 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -1176,6 +1176,7 @@ ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
> break; /* succeed */
> }
> num = *count;
> + cond_resched();
> }
> return ret;
> }
> diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> index 27967f9..cffc8cd 100644
> --- a/fs/ext3/balloc.c
> +++ b/fs/ext3/balloc.c
> @@ -735,6 +735,7 @@ bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
> struct journal_head *jh = bh2jh(bh);
>
> while (start < maxblocks) {
> + cond_resched();
> next = ext3_find_next_zero_bit(bh->b_data, maxblocks, start);
> if (next >= maxblocks)
> return -1;
I'm curious: Why schedule at the beginning of the while() loop rather
than at the end?
> @@ -1391,6 +1392,7 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
> break; /* succeed */
> }
> num = *count;
> + cond_resched();
> }
> out:
> if (ret >= 0) {
> --
> 1.6.2.2
I like this patch in general, but I worry about introducing new
performance problems in other cases. Have you guys tested on single
cpu systems? Maybe with a file system close to ENOSPC or badly
fragmented?
-VAL
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