On Wed, 2010-08-04 at 14:11 -0700, Yudong Gao wrote: > Thanks for the reply, Andy! > > So the write delegation can only reduce the unnecessary open/close and > lock/locku. But if a client modify the same page for multiple times, > e.g. editing the file in a editor, is there any optimization to > prevent the client from sending the half-updated pages? Ideally only > the final update need to be put on the wire. > Yes. However that optimisation is not linked to whether or not we hold a write delegation. The NFS client assumes close-to-open cache consistency, and so will cache writes until either the VM tries to reclaim memory by writing out dirty page, or the application calls one of fcntl(F_UNLCK), fsync() or close(). Trond > Thanks! > > best, > > Yudong > > On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <andros@xxxxxxxxxx> wrote: > > > > On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote: > > > >> Hi, > >> > >> I am not able to find the implementation of directory delegation, > >> either. Similarly, the callback functions CB_NOTIFY is not > >> implemented, either. I find that in preprocss_nfs41_op() in > >> callback_xdr.c, whenever a CB_NOTIFY is encountered, an > >> NFS4ERR_NOTSUPP is returned directly. > > > > CB_NOTIFY is not currently supported on the Linux NFS client. > > > >> > >> Am I missing something? Or they are just not supported in the current version? > >> > >> Thanks a lot! > >> > >> best, > >> > >> Yudong > >> > >> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <stgyd@xxxxxxxxx> wrote: > >>> Hi, > >>> > >>> I am looking at the delegation implementation in the source code of > >>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation, > >>> which is working and can serve the read requests locally. But I can > >>> never find the code about write delegation, which is supposed to cache > >>> the write update locally. I try to look at the functions including > >>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the > >>> write delegation. > >>> > >>> Is write delegation currently implemented in NFS 4.1? > > > > Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire. > > > > -->Andy > > > >>> > >>> Thanks! > >>> > >>> best, > >>> > >>> Yudong > >>> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
