linux-kernel - Re: nfs broken in net-next? -- now in mainline -- bisected: d9f5950f90292f7cc42834338dfd5f44dc4cc4ca

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Date:	Sat, 12 Dec 2009 17:57:51 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>
Cc:	mingo@...e.hu, sri@...ibm.com, herbert@...dor.apana.org.au,
	torvalds@...ux-foundation.org, sjayaraman@...e.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: nfs broken in net-next? -- now in mainline -- bisected: 
	d9f5950f90292f7cc42834338dfd5f44dc4cc4ca

On Sat, Dec 12, 2009 at 5:05 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>
> [f86dcc5aa8c7908f2c287e7a211228df599e3e71] udp: dynamically
> size hash tables at boot time

commit f86dcc5aa8c7908f2c287e7a211228df599e3e71
Author: Eric Dumazet <eric.dumazet@...il.com>
Date:   Wed Oct 7 00:37:59 2009 +0000

    udp: dynamically size hash tables at boot time

    UDP_HTABLE_SIZE was initialy defined to 128, which is a bit small for
    several setups.

    4000 active UDP sockets -> 32 sockets per chain in average. An
    incoming frame has to lookup all sockets to find best match, so long
    chains hurt latency.

    Instead of a fixed size hash table that cant be perfect for every
    needs, let UDP stack choose its table size at boot time like tcp/ip
    route, using alloc_large_system_hash() helper

    Add an optional boot parameter, uhash_entries=x so that an admin can
    force a size between 256 and 65536 if needed, like thash_entries and
    rhash_entries.

    dmesg logs two new lines :
    [    0.647039] UDP hash table entries: 512 (order: 0, 4096 bytes)
    [    0.647099] UDP Lite hash table entries: 512 (order: 0, 4096 bytes)

    Maximal size on 64bit arches would be 65536 slots, ie 1 MBytes for non
    debugging spinlocks.

    Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>

cause the problem: nfs mount fail.

the setup is:
64bit kernel, have all needed drivers in kernel, and boot with
ip=dhcp, root disk is 256M ramdisk.
then try to mount nfs....

YH
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