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Date:	Sat, 12 Dec 2009 18:25:22 -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 5:57 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> 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....
>

change entries default value from 65536 to 256,
nfs mount will work.

YH

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1f95348..57c13c3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2054,7 +2054,7 @@ void udp4_proc_exit(void)
 }
 #endif /* CONFIG_PROC_FS */

-static __initdata unsigned long uhash_entries;
+static __initdata unsigned long uhash_entries = UDP_HTABLE_SIZE_MIN;
 static int __init set_uhash_entries(char *str)
 {
        if (!str)
--
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