This is a note to let you know that I've just added the patch titled
nfs: fix high load average due to callback thread sleeping
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfs-fix-high-load-average-due-to-callback-thread-sleeping.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5d05e54af3cdbb13cf19c557ff2184781b91a22c Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Date: Fri, 20 Mar 2015 15:15:14 -0400
Subject: nfs: fix high load average due to callback thread sleeping
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From: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
commit 5d05e54af3cdbb13cf19c557ff2184781b91a22c upstream.
Chuck pointed out a problem that crept in with commit 6ffa30d3f734 (nfs:
don't call blocking operations while !TASK_RUNNING). Linux counts tasks
in uninterruptible sleep against the load average, so this caused the
system's load average to be pinned at at least 1 when there was a
NFSv4.1+ mount active.
Not a huge problem, but it's probably worth fixing before we get too
many complaints about it. This patch converts the code back to use
TASK_INTERRUPTIBLE sleep, simply has it flush any signals on each loop
iteration. In practice no one should really be signalling this thread at
all, so I think this is reasonably safe.
With this change, there's also no need to game the hung task watchdog so
we can also convert the schedule_timeout call back to a normal schedule.
Reported-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
Tested-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Fixes: commit 6ffa30d3f734 (“nfs: don't call blocking . . .”)
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/nfs/callback.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -128,7 +128,7 @@ nfs41_callback_svc(void *vrqstp)
if (try_to_freeze())
continue;
- prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
spin_lock_bh(&serv->sv_cb_lock);
if (!list_empty(&serv->sv_cb_list)) {
req = list_first_entry(&serv->sv_cb_list,
@@ -142,10 +142,10 @@ nfs41_callback_svc(void *vrqstp)
error);
} else {
spin_unlock_bh(&serv->sv_cb_lock);
- /* schedule_timeout to game the hung task watchdog */
- schedule_timeout(60 * HZ);
+ schedule();
finish_wait(&serv->sv_cb_waitq, &wq);
}
+ flush_signals(current);
}
return 0;
}
Patches currently in stable-queue which might be from jlayton@xxxxxxxxxxxxxxx are
queue-4.0/nfs-fix-high-load-average-due-to-callback-thread-sleeping.patch
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