xfs
[Top] [All Lists]

[PATCH V2] XFS: Don't wake xfsbufd when idle

To: Alex Elder <aelder@xxxxxxx>
Subject: [PATCH V2] XFS: Don't wake xfsbufd when idle
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 15 Jan 2010 09:45:07 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1AB9A794DBDDF54A8A81BE2296F7BDFE012A696D@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <1263210599-25067-4-git-send-email-david@xxxxxxxxxxxxx> <1AB9A794DBDDF54A8A81BE2296F7BDFE012A696D@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Thu, Jan 14, 2010 at 10:51:25AM -0600, Alex Elder wrote:
> Dave Chinner wrote:
> > The xfsbufd wakes every xfsbufd_centisecs (once per second by
> > default) for each filesystem even when the filesystem is idle.
> > If the xfsbufd has nothing to do, put it into a long term sleep
> > and only wake it up when there is work pending (i.e. dirty
> > buffers to flush soon). This will make laptop power misers happy.
> 
> Patch generally looks good but I have a question, below.

> >     do {
> > +           long    age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
> > +           long    tout = age;
> 
> Why do you switch from using xfs_buf_timer_centisecs to
> using xfs_buf_age_centisecs for the timeout (in the non-empty
> delwrite queue case)?

Because it's a bug? It should be xfs_buf_timer_centisecs
here. Good catch, Alex. :)

Updated patch below

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

XFS: Don't wake xfsbufd when idle V2

The xfsbufd wakes every xfsbufd_centisecs (once per second by
default) for each filesystem even when the filesystem is idle.
If the xfsbufd has nothing to do, put it into a long term sleep
and only wake it up when there is work pending (i.e. dirty
buffers to flush soon). This will make laptop power misers happy.

---
V2: fix xfsbufd timer interval

 fs/xfs/linux-2.6/xfs_buf.c |   20 +++++++++++++++-----
 1 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 77b8be8..18ae3ba 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -1595,6 +1595,11 @@ xfs_buf_delwri_queue(
                list_del(&bp->b_list);
        }
 
+       if (list_empty(dwq)) {
+               /* start xfsbufd as it is about to have something to do */
+               wake_up_process(bp->b_target->bt_task);
+       }
+
        bp->b_flags |= _XBF_DELWRI_Q;
        list_add_tail(&bp->b_list, dwq);
        bp->b_queuetime = jiffies;
@@ -1644,6 +1649,8 @@ xfsbufd_wakeup(
        list_for_each_entry(btp, &xfs_buftarg_list, bt_list) {
                if (test_bit(XBT_FORCE_SLEEP, &btp->bt_flags))
                        continue;
+               if (list_empty(&btp->bt_delwrite_queue))
+                       continue;
                set_bit(XBT_FORCE_FLUSH, &btp->bt_flags);
                wake_up_process(btp->bt_task);
        }
@@ -1708,6 +1715,9 @@ xfsbufd(
        set_freezable();
 
        do {
+               long    age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
+               long    tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
+
                if (unlikely(freezing(current))) {
                        set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
                        refrigerator();
@@ -1715,12 +1725,12 @@ xfsbufd(
                        clear_bit(XBT_FORCE_SLEEP, &target->bt_flags);
                }
 
-               schedule_timeout_interruptible(
-                       xfs_buf_timer_centisecs * msecs_to_jiffies(10));
-
-               xfs_buf_delwri_split(target, &tmp,
-                               xfs_buf_age_centisecs * msecs_to_jiffies(10));
+               /* sleep for a long time if there is nothing to do. */
+               if (list_empty(&target->bt_delwrite_queue))
+                       tout = MAX_SCHEDULE_TIMEOUT;
+               schedule_timeout_interruptible(tout);
 
+               xfs_buf_delwri_split(target, &tmp, age);
                count = 0;
                while (!list_empty(&tmp)) {
                        bp = list_entry(tmp.next, xfs_buf_t, b_list);

<Prev in Thread] Current Thread [Next in Thread>