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SubjectRe: [PATCH 10/17] writeback: avoid extra sync work at enqueue time
On Fri 06-05-11 11:08:31, Wu Fengguang wrote:
> This removes writeback_control.wb_start and does more straightforward
> sync livelock prevention by setting .older_than_this to prevent extra
> inodes from being enqueued in the first place.
>
> CC: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>

Honza

> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> fs/fs-writeback.c | 16 +++-------------
> include/linux/writeback.h | 3 ---
> 2 files changed, 3 insertions(+), 16 deletions(-)
>
> --- linux-next.orig/fs/fs-writeback.c 2011-05-05 23:30:29.000000000 +0800
> +++ linux-next/fs/fs-writeback.c 2011-05-05 23:30:30.000000000 +0800
> @@ -544,15 +544,6 @@ static int writeback_sb_inodes(struct su
> continue;
> }
>
> - /*
> - * Was this inode dirtied after sync_sb_inodes was called?
> - * This keeps sync from extra jobs and livelock.
> - */
> - if (inode_dirtied_after(inode, wbc->wb_start)) {
> - spin_unlock(&inode->i_lock);
> - return 1;
> - }
> -
> __iget(inode);
>
> pages_skipped = wbc->pages_skipped;
> @@ -585,9 +576,6 @@ static void __writeback_inodes_wb(struct
> {
> int ret = 0;
>
> - if (!wbc->wb_start)
> - wbc->wb_start = jiffies; /* livelock avoidance */
> -
> while (!list_empty(&wb->b_io)) {
> struct inode *inode = wb_inode(wb->b_io.prev);
> struct super_block *sb = inode->i_sb;
> @@ -686,7 +674,9 @@ static long wb_writeback(struct bdi_writ
> if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync)
> write_chunk = LONG_MAX;
>
> - wbc.wb_start = jiffies; /* livelock avoidance */
> + oldest_jif = jiffies;
> + wbc.older_than_this = &oldest_jif;
> +
> for (;;) {
> /*
> * Stop writeback when nr_pages has been consumed
> --- linux-next.orig/include/linux/writeback.h 2011-05-05 23:30:28.000000000 +0800
> +++ linux-next/include/linux/writeback.h 2011-05-05 23:30:30.000000000 +0800
> @@ -26,9 +26,6 @@ struct writeback_control {
> enum writeback_sync_modes sync_mode;
> unsigned long *older_than_this; /* If !NULL, only write back inodes
> older than this */
> - unsigned long wb_start; /* Time writeback_inodes_wb was
> - called. This is needed to avoid
> - extra jobs and livelock */
> long nr_to_write; /* Write this many pages, and decrement
> this for each page written */
> long pages_skipped; /* Pages which were not written */
>
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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