[patch] Re: Does XFS prevent disk spindown?

David Chinner
2008-04-09T04:10:55Z

On Tue, Apr 08, 2008 at 07:53:13AM +0200, Thor Kristoffersen wrote:
> David Chinner <dgc@sgi.com> writes:
> >> > What does 'xfs_logprint -t' show in these "idle" states
> >> > after these writes?
> >>
> >> xfs_logprint produces output like the one shown below, so it does indeed
> >> look like it's writing to the journal. But why should it need to keep
> >> writing to the journal when there have been no updates to any files on that
> >> partition recently?
> >
> > Are you using lazy-count=1? (i.e. output of 'xfs_info <mtpt>', please).
>
> Looks like I am:
>
> meta-data=/dev/sda3 isize=256 agcount=4, agsize=42676171 blks
> = sectsz=512 attr=2
> data = bsize=4096 blocks=170704681, imaxpct=25
> = sunit=0 swidth=0 blks
> naming =version 2 bsize=4096
> log =internal bsize=4096 blocks=32768, version=2
> = sectsz=512 sunit=0 blks, lazy-count=1
> realtime =none extsz=4096 blocks=0, rtextents=0
>
> Is that what's causing it? I have never specified any lazy-count option
> when I created or mounted the filesystem. I didn't even know it existed.

Introduced in 2.6.22, and recently was made the default mkfs config.

Try the patch below.

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group

Remove periodic logging of in-core superblock counters.

xfssyncd triggers the logging of superblock counters every
30s if the filesystem is made with lazy-count=1. This will
prevent disks from idling and spinning down as there will
be a log write every 30s. With the way counter recovery
works for lazy-count=1, this code is unnecessary and provides
no real benefit, so just remove it.

Signed-off-by: Dave Chinner <dgc@sgi.com>
---
fs/xfs/linux-2.6/xfs_super.c | 3 +--
fs/xfs/linux-2.6/xfs_vfs.h | 1 -
fs/xfs/xfs_vfsops.c | 10 ----------
3 files changed, 1 insertion(+), 13 deletions(-)

Index: 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- 2.6.x-xfs-new.orig/fs/xfs/linux-2.6/xfs_super.c 2008-04-02 09:25:11.000000000 +1000
+++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_super.c 2008-04-02 10:02:25.391897032 +1000
@@ -1028,8 +1028,7 @@ xfs_sync_worker(
int error;

if (!(mp->m_flags & XFS_MOUNT_RDONLY))
- error = xfs_sync(mp, SYNC_FSDATA | SYNC_BDFLUSH | SYNC_ATTR |
- SYNC_REFCACHE | SYNC_SUPER);
+ error = xfs_sync(mp, SYNC_FSDATA | SYNC_BDFLUSH | SYNC_ATTR);
mp->m_sync_seq++;
wake_up(&mp->m_wait_single_sync_task);
}
Index: 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_vfs.h
===================================================================
--- 2.6.x-xfs-new.orig/fs/xfs/linux-2.6/xfs_vfs.h 2007-08-24 22:25:22.000000000 +1000
+++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_vfs.h 2008-04-02 10:02:52.596414152 +1000
@@ -49,7 +49,6 @@ typedef struct bhv_vfs_sync_work {
#define SYNC_REFCACHE 0x0040 /* prune some of the nfs ref cache */
#define SYNC_REMOUNT 0x0080 /* remount readonly, no dummy LRs */
#define SYNC_IOWAIT 0x0100 /* wait for all I/O to complete */
-#define SYNC_SUPER 0x0200 /* flush superblock to disk */

/*
* When remounting a filesystem read-only or freezing the filesystem,
Index: 2.6.x-xfs-new/fs/xfs/xfs_vfsops.c
===================================================================
--- 2.6.x-xfs-new.orig/fs/xfs/xfs_vfsops.c 2008-04-02 09:00:55.000000000 +1000
+++ 2.6.x-xfs-new/fs/xfs/xfs_vfsops.c 2008-04-02 10:01:35.534280170 +1000
@@ -1334,18 +1334,8 @@ xfs_syncsub(
}

/*
- * If asked, update the disk superblock with incore counter values if we
- * are using non-persistent counters so that they don't get too far out
- * of sync if we crash or get a forced shutdown. We don't want to force
- * this to disk, just get a transaction into the iclogs....
- */
- if (flags & SYNC_SUPER)
- xfs_log_sbcount(mp, 0);
-
- /*
* Now check to see if the log needs a "dummy" transaction.
*/
-
if (!(flags & SYNC_REMOUNT) && xfs_log_need_covered(mp)) {
xfs_trans_t *tp;
xfs_inode_t *ip;