xfs buffers

[kanishk rastogi]

inline...

On Fri, Aug 14, 2009 at 1:57 PM, Russell Cattelan <cattelan at thebarn.com>wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> kanishk rastogi wrote:
> > hi all, I was trying to understand the xfs_buf_t management in XFS.
> >  I was looking at the xfs_bufhash_t which is used to keep the info
> > of buffers which have ongoing transactions. I wanted to know if it
> > uses it for caching these pages.
> >
> > As far as i can see in xfs_buf_relse  calls ::
> >
> > list_del_init(&bp->b_hash_list);
> >
> > if the count drops down to 0 for the buffer...
> >
> > if (atomic_dec_and_lock(&bp->b_hold, &hash->bh_lock)) { if
> > (bp->b_relse) { ----->set only in case of error??
> > atomic_inc(&bp->b_hold); spin_unlock(&hash->bh_lock);
> > (*(bp->b_relse)) (bp); } else if (bp->b_flags & XBF_FS_MANAGED) {
> > ----> mostly unset......\
> Indeed. that flag is used on exactly one buffer, the superblock.ode of the
> Basically the superblock is pinned in memory and only flushed by the
> filesystem.
> > spin_unlock(&hash->bh_lock); } else { ASSERT(!(bp->b_flags &
> > (XBF_DELWRI|_XBF_DELWRI_Q))); *list_del_init(&bp->b_hash_list);*
> > spin_unlock(&hash->bh_lock); xfs_buf_free(bp); } }
>


>
> >
> > ---------------
> >
> > CMIIW: So it doesnt keeps buffers if they are not in use....  ??
> buffers are released back to the buf_t  zone when they are done.
>
> zone allocation / free is very fast so managing lists of "free"
> buffers doesn't make a lot of sense.
>

sorry my fault i was asking about the pages these buffers point to? ....
I see them being pickd from the device inode of the monted device...

thankx
kanishk

>
> >
> > I dont think that should be the case...
> >
> > -- regards kanishk
> >
> > ----------------------------------------------------------------------
> >
> >
> > _______________________________________________ xfs mailing list
> > xfs at oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.7 (Darwin)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
>
> iD8DBQFKhaWBNRmM+OaGhBgRAtqgAJ9CZfj0QXz8Yy7P4jYemgEPsvR9pQCfcSWM
> a9OI8A4ckMdOuiXQ60o4PLE=
> =OJAD
> -----END PGP SIGNATURE-----
>
>


-- 
regards
kanishk
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://oss.sgi.com/pipermail/xfs/attachments/20090817/80535bb4/attachment.htm>