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To: dfr@render.com
Cc: henrich@crh.cl.msu.edu, lite2@freebsd.org
Subject: Re: Delayed write patch
In-Reply-To: Your message of "Wed, 9 Oct 1996 14:11:15 +0100 (BST)"
References: <Pine.BSF.3.95.961009141039.10204f-100000@minnow.render.com>
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Date: Wed, 09 Oct 1996 23:16:23 +0900
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From: Hidetoshi Shimokawa <simokawa@sat.t.u-tokyo.ac.jp>
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dfr> > I tried this patch, but there is no performance improvement.
dfr> > It's still around 300KB.
dfr> > 
dfr> > tcpdump shows that only one iod is running.
dfr> 
dfr> If you change nfs_asyncio to return EIO instead of using a delayed write,
dfr> how many iods are running?
if I start 4 iods, 4 iods are running.

observing by tcpdump,

1) without delayed write (800KB/s)

client		server
------------------------
req(async)
req(async)	
req(async)
req(async)
req(sync)
		rep
		rep
		rep
		rep
		rep
req
req
req
req
req
		rep
		rep
		rep
		rep
		rep
req
...

2) with delayed write (300KB/s)

client		server
------------------------
req
req
req
req
		rep
		rep
req
req
		rep
....
req
		rep
req
		rep
req
		rep
....

The following is the patch to control delayed write by sysctl.
(sorry, I don't know wether this is the right usage of sysctl)

*** nfs_bio.c.orig      Mon Sep 30 22:39:29 1996
--- nfs_bio.c   Wed Oct  9 23:13:25 1996
***************
*** 46,51 ****
--- 46,52 ----
  #include <sys/vnode.h>
  #include <sys/mount.h>
  #include <sys/kernel.h>
+ #include <sys/sysctl.h>
  
  #include <vm/vm.h>
  #include <vm/vm_param.h>
***************
*** 65,70 ****
--- 66,74 ----
  extern int nfs_numasync;
  extern struct nfsstats nfsstats;
  
+ int nfs_dwrite;
+ SYSCTL_INT(_vfs_nfs, OID_AUTO, dwrite, CTLFLAG_RW, &nfs_dwrite, 0, "");
+ 
  /*
   * Ifdefs for FreeBSD-current's merged VM/buffer cache. It is unfortunate
   * that this isn't done inside getblk() and brelse() so these calls
***************
*** 758,763 ****
--- 762,768 ----
         * is currently doing a write for this file and will pick up the
         * delayed writes before going back to sleep.
         */
+       if (!nfs_dwrite) return (EIO);
        bp->b_flags |= B_DELWRI;
        reassignbuf(bp, bp->b_vp);
        biodone(bp);

/\ Hidetoshi Shimokawa
\/  simokawa@sat.t.u-tokyo.ac.jp
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