From: Christoph Hellwig Subject: writeback: trace the source of writeback works Trace who queued up work to the flusher thread. Also add a new tracepoint to the failed grab_super_passive case. Signed-off-by: Christoph Hellwig Index: xfs/fs/fs-writeback.c =================================================================== --- xfs.orig/fs/fs-writeback.c 2011-08-01 17:59:15.318991514 +0200 +++ xfs/fs/fs-writeback.c 2011-08-01 18:31:33.221826327 +0200 @@ -41,7 +41,7 @@ struct wb_writeback_work { unsigned int for_kupdate:1; unsigned int range_cyclic:1; unsigned int for_background:1; - + enum writeback_reason why; struct list_head list; /* pending work list */ struct completion *done; /* set if the caller waits */ }; @@ -115,7 +115,7 @@ static void bdi_queue_work(struct backin static void __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages, - bool range_cyclic) + bool range_cyclic, enum writeback_reason why) { struct wb_writeback_work *work; @@ -135,6 +135,7 @@ __bdi_start_writeback(struct backing_dev work->sync_mode = WB_SYNC_NONE; work->nr_pages = nr_pages; work->range_cyclic = range_cyclic; + work->why = why; bdi_queue_work(bdi, work); } @@ -152,7 +153,7 @@ __bdi_start_writeback(struct backing_dev */ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages) { - __bdi_start_writeback(bdi, nr_pages, true); + __bdi_start_writeback(bdi, nr_pages, true, WB_START_WRITEBACK); } /** @@ -618,6 +619,7 @@ static long __writeback_inodes_wb(struct struct super_block *sb = inode->i_sb; if (!grab_super_passive(sb)) { + trace_writeback_grab_super_failed(wb->bdi, work); redirty_tail(inode, wb); continue; } @@ -636,12 +638,14 @@ static long __writeback_inodes_wb(struct return wrote; } -long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages) +long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, + enum writeback_reason why) { struct wb_writeback_work work = { .nr_pages = nr_pages, .sync_mode = WB_SYNC_NONE, .range_cyclic = 1, + .why = why, }; spin_lock(&wb->list_lock); @@ -813,6 +817,7 @@ static long wb_check_background_flush(st .sync_mode = WB_SYNC_NONE, .for_background = 1, .range_cyclic = 1, + .why = WB_BACKGROUND, }; return wb_writeback(wb, &work); @@ -846,6 +851,7 @@ static long wb_check_old_data_flush(stru .sync_mode = WB_SYNC_NONE, .for_kupdate = 1, .range_cyclic = 1, + .why = WB_OLD, }; return wb_writeback(wb, &work); @@ -977,7 +983,7 @@ void wakeup_flusher_threads(long nr_page list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { if (!bdi_has_dirty_io(bdi)) continue; - __bdi_start_writeback(bdi, nr_pages, false); + __bdi_start_writeback(bdi, nr_pages, false, WB_FLUSHER_THREADS); } rcu_read_unlock(); } @@ -1207,6 +1213,7 @@ void writeback_inodes_sb_nr(struct super .tagged_writepages = 1, .done = &done, .nr_pages = nr, + .why = WB_WRITEBACK_INODES, }; WARN_ON(!rwsem_is_locked(&sb->s_umount)); @@ -1285,6 +1292,7 @@ void sync_inodes_sb(struct super_block * .nr_pages = LONG_MAX, .range_cyclic = 0, .done = &done, + .why = WB_SYNC_INODES, }; WARN_ON(!rwsem_is_locked(&sb->s_umount)); Index: xfs/include/trace/events/writeback.h =================================================================== --- xfs.orig/include/trace/events/writeback.h 2011-08-01 17:58:27.649249764 +0200 +++ xfs/include/trace/events/writeback.h 2011-08-01 18:31:26.501862733 +0200 @@ -21,6 +21,16 @@ {I_REFERENCED, "I_REFERENCED"} \ ) +#define WB_TYPES \ + { WB_SYNC_INODES, "sync_inodes_sb" }, \ + { WB_WRITEBACK_INODES, "writeback_inodes_sb" }, \ + { WB_START_WRITEBACK, "bdi_start_writeback" }, \ + { WB_FLUSHER_THREADS, "wakeup_flusher_threads" }, \ + { WB_EMERGENCY, "emergency flush" }, \ + { WB_BALANCE, "balance_dirty_pages" }, \ + { WB_BACKGROUND, "wb_check_background_flush" }, \ + { WB_OLD, "wb_check_old_data_flush" } + struct wb_writeback_work; DECLARE_EVENT_CLASS(writeback_work_class, @@ -34,6 +44,7 @@ DECLARE_EVENT_CLASS(writeback_work_class __field(int, for_kupdate) __field(int, range_cyclic) __field(int, for_background) + __field(int, why) ), TP_fast_assign( strncpy(__entry->name, dev_name(bdi->dev), 32); @@ -43,16 +54,18 @@ DECLARE_EVENT_CLASS(writeback_work_class __entry->for_kupdate = work->for_kupdate; __entry->range_cyclic = work->range_cyclic; __entry->for_background = work->for_background; + __entry->why = work->why; ), TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d " - "kupdate=%d range_cyclic=%d background=%d", + "kupdate=%d range_cyclic=%d background=%d reason=%s", __entry->name, MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev), __entry->nr_pages, __entry->sync_mode, __entry->for_kupdate, __entry->range_cyclic, - __entry->for_background + __entry->for_background, + __print_symbolic(__entry->why, WB_TYPES) ) ); #define DEFINE_WRITEBACK_WORK_EVENT(name) \ @@ -65,6 +78,7 @@ DEFINE_WRITEBACK_WORK_EVENT(writeback_ex DEFINE_WRITEBACK_WORK_EVENT(writeback_start); DEFINE_WRITEBACK_WORK_EVENT(writeback_written); DEFINE_WRITEBACK_WORK_EVENT(writeback_wait); +DEFINE_WRITEBACK_WORK_EVENT(writeback_grab_super_failed); TRACE_EVENT(writeback_pages_written, TP_PROTO(long pages_written), Index: xfs/include/linux/writeback.h =================================================================== --- xfs.orig/include/linux/writeback.h 2011-08-01 18:24:26.754136700 +0200 +++ xfs/include/linux/writeback.h 2011-08-01 18:32:37.158146620 +0200 @@ -79,13 +79,26 @@ struct writeback_control { * fs/fs-writeback.c */ struct bdi_writeback; + +enum writeback_reason { + WB_SYNC_INODES, + WB_WRITEBACK_INODES, + WB_START_WRITEBACK, + WB_FLUSHER_THREADS, + WB_EMERGENCY, + WB_BALANCE, + WB_BACKGROUND, + WB_OLD, +}; + int inode_wait(void *); void writeback_inodes_sb(struct super_block *); void writeback_inodes_sb_nr(struct super_block *, unsigned long nr); int writeback_inodes_sb_if_idle(struct super_block *); int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr); void sync_inodes_sb(struct super_block *); -long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages); +long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, + enum writeback_reason why); long wb_do_writeback(struct bdi_writeback *wb, int force_wait); void wakeup_flusher_threads(long nr_pages); Index: xfs/mm/backing-dev.c =================================================================== --- xfs.orig/mm/backing-dev.c 2011-08-01 18:24:26.774136593 +0200 +++ xfs/mm/backing-dev.c 2011-08-01 18:25:09.910569569 +0200 @@ -456,7 +456,7 @@ static int bdi_forker_thread(void *ptr) * the bdi from the thread. Hopefully 1024 is * large enough for efficient IO. */ - writeback_inodes_wb(&bdi->wb, 1024); + writeback_inodes_wb(&bdi->wb, 1024, WB_EMERGENCY); } else { /* * The spinlock makes sure we do not lose Index: xfs/mm/page-writeback.c =================================================================== --- xfs.orig/mm/page-writeback.c 2011-08-01 18:24:26.794136483 +0200 +++ xfs/mm/page-writeback.c 2011-08-01 18:27:43.019740106 +0200 @@ -738,7 +738,8 @@ static void balance_dirty_pages(struct a trace_balance_dirty_start(bdi); if (bdi_nr_reclaimable > task_bdi_thresh) { pages_written += writeback_inodes_wb(&bdi->wb, - write_chunk); + write_chunk, + WB_BALANCE); trace_balance_dirty_written(bdi, pages_written); if (pages_written >= write_chunk) break; /* We've done our duty */