On 07/30/2013 05:59 AM, zwu.kernel@xxxxxxxxx wrote:
> From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
>
> It can take a long time to run log recovery operation because it is
> single threaded and is bound by read latency. We can find that it took
> most of the time to wait for the read IO to occur, so if one object
> readahead is introduced to log recovery, it will obviously reduce the
> log recovery time.
>
> Log recovery time stat:
>
> w/o this patch w/ this patch
>
> real: 0m15.023s 0m7.802s
> user: 0m0.001s 0m0.001s
> sys: 0m0.246s 0m0.107s
>
> Signed-off-by: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
> ---
Cool patch. I'm not terribly familiar with the log recovery code so take
my comments with a grain of salt, but a couple things I noticed on a
quick skim...
> fs/xfs/xfs_log_recover.c | 162 +++++++++++++++++++++++++++++++++++++++++++++--
> fs/xfs/xfs_log_recover.h | 2 +
> 2 files changed, 159 insertions(+), 5 deletions(-)
>
...
>
> +STATIC int
> +xlog_recover_items_pass2(
> + struct xlog *log,
> + struct xlog_recover *trans,
> + struct list_head *buffer_list,
> + struct list_head *ra_list)
A nit, but technically this function doesn't have to be involved with
readahead. Perhaps rename ra_list to item_list..?
> +{
> + int error = 0;
> + xlog_recover_item_t *item;
> +
> + list_for_each_entry(item, ra_list, ri_list) {
> + error = xlog_recover_commit_pass2(log, trans,
> + buffer_list, item);
> + if (error)
> + return error;
> + }
> +
> + return error;
> +}
> +
> /*
> * Perform the transaction.
> *
> @@ -3189,9 +3314,11 @@ xlog_recover_commit_trans(
> struct xlog_recover *trans,
> int pass)
> {
> - int error = 0, error2;
> - xlog_recover_item_t *item;
> + int error = 0, error2, ra_qdepth = 0;
> + xlog_recover_item_t *item, *next;
> LIST_HEAD (buffer_list);
> + LIST_HEAD (ra_list);
> + LIST_HEAD (all_ra_list);
>
> hlist_del(&trans->r_list);
>
> @@ -3199,14 +3326,21 @@ xlog_recover_commit_trans(
> if (error)
> return error;
>
> - list_for_each_entry(item, &trans->r_itemq, ri_list) {
> + list_for_each_entry_safe(item, next, &trans->r_itemq, ri_list) {
> switch (pass) {
> case XLOG_RECOVER_PASS1:
> error = xlog_recover_commit_pass1(log, trans, item);
> break;
> case XLOG_RECOVER_PASS2:
> - error = xlog_recover_commit_pass2(log, trans,
> - &buffer_list, item);
> + if (ra_qdepth++ >= XLOG_RECOVER_MAX_QDEPTH) {
The counting mechanism looks strange and easy to break with future
changes. Why not increment ra_qdepth in the else bracket where it is
explicitly tied to the operation it tracks?
> + error = xlog_recover_items_pass2(log, trans,
> + &buffer_list, &ra_list);
> + list_splice_tail_init(&ra_list, &all_ra_list);
> + ra_qdepth = 0;
So now we've queued up a bunch of items we've issued readahead on in
ra_list and we've executed the recovery on the list. What happens to the
current item?
Brian
> + } else {
> + xlog_recover_ra_pass2(log, item);
> + list_move_tail(&item->ri_list, &ra_list);
> + }
> break;
> default:
> ASSERT(0);
> @@ -3216,9 +3350,27 @@ xlog_recover_commit_trans(
> goto out;
> }
>
> + if (!list_empty(&ra_list)) {
> + error = xlog_recover_items_pass2(log, trans,
> + &buffer_list, &ra_list);
> + if (error)
> + goto out;
> +
> + list_splice_tail_init(&ra_list, &all_ra_list);
> + }
> +
> + if (!list_empty(&all_ra_list))
> + list_splice_init(&all_ra_list, &trans->r_itemq);
> +
> xlog_recover_free_trans(trans);
>
> out:
> + if (!list_empty(&ra_list))
> + list_splice_tail_init(&ra_list, &all_ra_list);
> +
> + if (!list_empty(&all_ra_list))
> + list_splice_init(&all_ra_list, &trans->r_itemq);
> +
> error2 = xfs_buf_delwri_submit(&buffer_list);
> return error ? error : error2;
> }
> diff --git a/fs/xfs/xfs_log_recover.h b/fs/xfs/xfs_log_recover.h
> index 1c55ccb..16322f6 100644
> --- a/fs/xfs/xfs_log_recover.h
> +++ b/fs/xfs/xfs_log_recover.h
> @@ -63,4 +63,6 @@ typedef struct xlog_recover {
> #define XLOG_RECOVER_PASS1 1
> #define XLOG_RECOVER_PASS2 2
>
> +#define XLOG_RECOVER_MAX_QDEPTH 100
> +
> #endif /* __XFS_LOG_RECOVER_H__ */
>
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