Re: [PATCH 22/35] writeback: trace global dirty page states

Wu Fengguang
2010-12-17T03:11:12Z

On Fri, Dec 17, 2010 at 10:19:34AM +0800, Wu Fengguang wrote:
> On Mon, Dec 13, 2010 at 10:47:08PM +0800, Wu, Fengguang wrote:
>
> > + TP_fast_assign(
> > + strlcpy(__entry->bdi,
> > + dev_name(mapping->backing_dev_info->dev), 32);
> > + __entry->ino = mapping->host->i_ino;
>
> I got an oops against the above line on shmem. Can be fixed by the
> below patch, but still not 100% confident..

btw, here is a cleanup of the tracepoint.

Thanks,
Fengguang
---
Subject: writeback: simplify and rename tracepoint balance_dirty_state to global_dirty_state
Date: Fri Dec 17 10:37:35 CST 2010

Make it a more clean interface, and also track the background flusher
when it calls over_bground_thresh() to check the global limits.

The removed information could go into tracepoint balance_dirty_pages.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/trace/events/writeback.h | 37 +++++++----------------------
mm/page-writeback.c | 16 +++---------
2 files changed, 13 insertions(+), 40 deletions(-)

--- linux-next.orig/include/trace/events/writeback.h 2010-12-17 11:05:08.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2010-12-17 11:06:20.000000000 +0800
@@ -149,60 +149,41 @@ DEFINE_WBC_EVENT(wbc_writeback_written);
DEFINE_WBC_EVENT(wbc_writeback_wait);
DEFINE_WBC_EVENT(wbc_writepage);

-TRACE_EVENT(balance_dirty_state,
+TRACE_EVENT(global_dirty_state,

- TP_PROTO(struct address_space *mapping,
- unsigned long nr_dirty,
- unsigned long nr_writeback,
- unsigned long nr_unstable,
- unsigned long background_thresh,
+ TP_PROTO(unsigned long background_thresh,
unsigned long dirty_thresh
),

- TP_ARGS(mapping,
- nr_dirty,
- nr_writeback,
- nr_unstable,
- background_thresh,
+ TP_ARGS(background_thresh,
dirty_thresh
),

TP_STRUCT__entry(
- __array(char, bdi, 32)
- __field(unsigned long, ino)
__field(unsigned long, nr_dirty)
__field(unsigned long, nr_writeback)
__field(unsigned long, nr_unstable)
__field(unsigned long, background_thresh)
__field(unsigned long, dirty_thresh)
- __field(unsigned long, task_dirtied_pause)
),

TP_fast_assign(
- strlcpy(__entry->bdi,
- dev_name(mapping->backing_dev_info->dev), 32);
- __entry->ino = mapping->host->i_ino;
- __entry->nr_dirty = nr_dirty;
- __entry->nr_writeback = nr_writeback;
- __entry->nr_unstable = nr_unstable;
+ __entry->nr_dirty = global_page_state(NR_FILE_DIRTY);
+ __entry->nr_writeback = global_page_state(NR_WRITEBACK);
+ __entry->nr_unstable = global_page_state(NR_UNSTABLE_NFS);
__entry->background_thresh = background_thresh;
__entry->dirty_thresh = dirty_thresh;
- __entry->task_dirtied_pause = current->nr_dirtied_pause;
),

- TP_printk("bdi %s: dirty=%lu wb=%lu unstable=%lu "
- "bg_thresh=%lu thresh=%lu gap=%ld "
- "poll_thresh=%lu ino=%lu",
- __entry->bdi,
+ TP_printk("dirty=%lu writeback=%lu unstable=%lu "
+ "bg_thresh=%lu thresh=%lu gap=%ld",
__entry->nr_dirty,
__entry->nr_writeback,
__entry->nr_unstable,
__entry->background_thresh,
__entry->dirty_thresh,
__entry->dirty_thresh - __entry->nr_dirty -
- __entry->nr_writeback - __entry->nr_unstable,
- __entry->task_dirtied_pause,
- __entry->ino
+ __entry->nr_writeback - __entry->nr_unstable
)
);

--- linux-next.orig/mm/page-writeback.c 2010-12-17 11:05:08.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-12-17 11:05:09.000000000 +0800
@@ -418,6 +418,7 @@ void global_dirty_limits(unsigned long *
}
*pbackground = background;
*pdirty = dirty;
+ trace_global_dirty_state(background, dirty);
}

/**
@@ -712,21 +713,12 @@ static void balance_dirty_pages(struct a
* written to the server's write cache, but has not yet
* been flushed to permanent storage.
*/
- nr_reclaimable = global_page_state(NR_FILE_DIRTY);
- bdi_dirty = global_page_state(NR_UNSTABLE_NFS);
- nr_dirty = global_page_state(NR_WRITEBACK);
+ nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
+ nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);

global_dirty_limits(&background_thresh, &dirty_thresh);

- trace_balance_dirty_state(mapping,
- nr_reclaimable,
- nr_dirty,
- bdi_dirty,
- background_thresh,
- dirty_thresh);
- nr_reclaimable += bdi_dirty;
- nr_dirty += nr_reclaimable;
-
/*
* Throttle it only when the background writeback cannot
* catch-up. This avoids (excessively) small writeouts