Re: [patch] remove unnecessary periodic superblock logging.

[Timothy Shimmin <tes@xxxxxxx>]

Barry Naujok wrote:
> On Thu, 10 Apr 2008 14:20:01 +1000, David Chinner <dgc@xxxxxxx> wrote:
>
> > 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.
> I'm happy with this (xfs_initialize_perag_data() does the
> global counter recovery during mount).
So we only do the sb count logging at unmount type times...
xfs_attr_quiesce() and xfs_unmountfs(),
when no log recovery will happen.
Hmmm...so why do we have to log it out at these times?
I'm forgetting how this works.

--Tim


> > Signed-off-by: Dave Chinner <dgc@xxxxxxx>
> > ---
> >  fs/xfs/linux-2.6/xfs_super.c |    3 +--
> >  fs/xfs/linux-2.6/xfs_vfs.h   |    1 -
> >  fs/xfs/xfs_vfsops.c          |   13 -------------
> >  3 files changed, 1 insertion(+), 16 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    2008-04-10 
> > 10:02:14.000000000 +1000
> > +++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_super.c    2008-04-10 
> > 10:02:58.419346393 +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    2008-04-10 
> > 10:00:25.000000000 +1000
> > +++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_vfs.h    2008-04-10 
> > 10:02:58.419346393 +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    2008-04-10 
> > 10:01:54.000000000 +1000
> > +++ 2.6.x-xfs-new/fs/xfs/xfs_vfsops.c    2008-04-10 10:03:35.288729547 
> > +1000
> > @@ -1326,21 +1326,8 @@ 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) {
> > -        error = xfs_log_sbcount(mp, 0);
> > -        if (error)
> > -            last_error = error;
> > -    }
> > -
> > -    /*
> >       * 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;