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Date:      Sun, 7 Jul 2002 20:56:38 +0400 (MSD)
From:      "Roman V. Palagin" <romanp@unshadow.net>
To:        John Polstra <jdp@polstra.com>
Cc:        stable@FreeBSD.ORG
Subject:   Re: NFS errors at high hz values with TCP mounts
Message-ID:  <20020707205408.Y416-100000@room101.wuppy.net.ru>
In-Reply-To: <200207062254.g66MsJPj000565@vashon.polstra.com>

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On Jul 6, at 3:54pm -0700, John Polstra wrote:

> > > Here's what happens when I try to copy a 512 kbyte file from the
> > > hz=10000 client to a server that is NFS-mounted:
> > >
> > >     thin$ dd if=/dev/zero of=/mnt/foo count=1000
> > >     dd: /mnt/foo: Resource temporarily unavailable
> > >     61+0 records in
> > >     60+0 records out
> > >     30720 bytes transferred in 0.000996 secs (30843571 bytes/sec)
> >
> > I forget to mention that this message appears in the dmesg output on
> > the client machine:
> >
> >     nfs send error 35 for server strings:/usr/home/jdp
> >
> > It comes from sys/nfs/nfs_socket.c line 499.
>
> Sorry for the extended conversation with myself. :-)  I think I
> found the bug.  In nfs_connect() at line 300 of sys/nfs/nfs_socket.c
> we have this code:
>
>         so->so_rcv.sb_timeo = (5 * hz);
>         so->so_snd.sb_timeo = (5 * hz);
>
> But sb_timeo has type "short", which overflows when hz is 10000.
>
> This is in struct sockbuf.  I don't think it would break binary
> compatibility with existing 3rd party modules to change it to type
> "long".  Are there any contrary opinions?

I see this problem with HZ=1000, overflow doesn't occured in this
situation... May be problem lies somewhere else?

                                             - Roman
---
Any opinions in this posting are my own and not those of my present
or previous employers.


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