Re: NFS client write performance issue ... thoughts?

[<trond.myklebust@fys.uio.no>]

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På to , 08/01/2004 klokka 12:47, skreiv Paul Smith:
> Do you know when those accounting errors were fixed?

In the official kernels? 2.4.22, I believe... However there are patches
going back to 2.4.19...

See http://www.fys.uio.no/~trondmy/src/Linux-2.4.x/2.4.19/

The main patch you want will be linux-2.4.19-14-call_start.dif

>
> ClearCase implements its own virtual filesystem type, and so is
> heavily tied to specific kernels (the kernel module is not open source
> of course :( ).  We basically can move to any kernel that has been
> released as part of an official Red Hat release (say, 2.4.20-8 from
> RH9 would work), but no other kernels can be used (the ClearCase
> kernel module has checks on the sizes of various kernel structures and
> won't load if they're not what it thinks they should be--and since
> it's a filesystem it cares deeply about structures that have tended to
> change a lot.  It won't even work with vanilla kernel.org kernels of
> the same version.)

Blech...

Note: if you want to try implementing a scheme like what you propose,
then the simplest way to do it, would be to add something like the
following patch. It disables nfs_strategy(), then causes
nfs_updatepage() to extend the request size if it sees that we're not
using byte-range locking, and the complete page is in cache.

Cheers,
  Trond



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--- linux-2.4.23-rc1/fs/nfs/write.c.orig	2003-11-16 19:24:23.000000000 -0500
+++ linux-2.4.23-rc1/fs/nfs/write.c	2004-01-09 16:25:18.000000000 -0500
@@ -746,6 +746,7 @@ nfs_update_request(struct file* file, st
 static void
 nfs_strategy(struct inode *inode)
 {
+#if 0
 	unsigned int	dirty, wpages;
 
 	dirty  = inode->u.nfs_i.ndirty;
@@ -760,6 +761,7 @@ nfs_strategy(struct inode *inode)
 	if (dirty >= NFS_STRATEGY_PAGES * wpages)
 		nfs_flush_file(inode, NULL, 0, 0, 0);
 #endif
+#endif
 }
 
 int
@@ -849,8 +851,19 @@ nfs_updatepage(struct file *file, struct
 		SetPageUptodate(page);
 		nfs_unlock_request(req);
 		nfs_strategy(inode);
-	} else
+	} else {
+		/* If we are not locking, and the page is up to date,
+		 * we may write out the entire page for efficiency.
+		 */
+		if (Page_Uptodate(page) && inode->i_flock == 0) {
+			req->wb_offset = 0;
+			if (page->index < (inode->i_size >> PAGE_CACHE_SHIFT))
+				req->wb_bytes = PAGE_CACHE_SIZE;
+			else
+				req->wb_bytes = inode->i_size & PAGE_CACHE_MASK;
+		}
 		nfs_unlock_request(req);
+	}
 done:
         dprintk("NFS:      nfs_updatepage returns %d (isize %Ld)\n",
                                                 status, (long long)inode->i_size);