netdev - Re: cat /proc/net/tcp takes 0.5 seconds on x86

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Message-ID: <48B5F3E2.2000909@cosmosbay.com>
Date:	Thu, 28 Aug 2008 02:40:02 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	David Miller <davem@...emloft.net>
Cc:	andi@...stfloor.org, davej@...hat.com, netdev@...r.kernel.org,
	j.w.r.degoede@....nl
Subject: Re: cat /proc/net/tcp takes 0.5 seconds on x86_64

David Miller a écrit :
> From: Eric Dumazet <dada1@...mosbay.com>
> Date: Thu, 28 Aug 2008 01:43:31 +0200
> 
>> David Miller a écrit :
>>> From: Eric Dumazet <dada1@...mosbay.com>
>>> Date: Thu, 28 Aug 2008 01:09:19 +0200
>>>
>>>> Not really, I suspect commit (a7ab4b501f9b8a9dc4d5cee542db67b6ccd1088b [TCPv4]: Improve BH latency in /proc/net/tcp) is responsible for longer delays.
>>>> Note that its rather old :
>>>  ...
>>>> We used to disable bh once, while reading the table. This sucked.
>>>>
>>>> In case machine is handling trafic, we now are preemptable by softirqs
>>>> while reading /proc/net/tcp. Thats a good thing.
>>> Yes, that would account for it, good spotting.
>>>
>>>> By the way, I find Andi patch usefull. Same thing could be done for /proc/net/rt_cache.
>>> Fair enough.  If you can cook up a quick rt_cache patch I'll toss it and
>>> Andi's patch into net-next so it can cook for a while.
>> Well, first patch I would like to submit is about letting netlink being able to be faster than /proc/net/tcp again :)
> 
> Andi just posted a very similar patch :)

No problem :)

Here is the patch for /proc/net/rt_cache (legacy /proc and netlink interface)

Thank you

[PATCH] ip: speedup /proc/net/rt_cache handling

When scanning route cache hash table, we can avoid taking locks for empty buckets.
Both /proc/net/rt_cache and NETLINK RTM_GETROUTE interface are taken into account.

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>


View attachment "route.patch" of type "text/plain" (1505 bytes)