From: Nicolas Dichtel <nicolas.dichtel@6wind•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: netdev <netdev@vger•kernel.org>
Subject: Re: [RFC PATCH] ipv4: release dev refcnt early when destroying inetdev
Date: Fri, 10 Sep 2010 16:57:16 +0200 [thread overview]
Message-ID: <4C8A474C.3040502@6wind.com> (raw)
In-Reply-To: <1284128679.24675.38.camel@edumazet-laptop>
Le 10.09.2010 16:24, Eric Dumazet a écrit :
> Le vendredi 10 septembre 2010 à 15:35 +0200, Nicolas Dichtel a écrit :
>> Hi all,
>>
>> We got a scalability problem when we try to remove a lot of virtual interfaces.
>> After analysis, we found that a refcnt on a device was released too late.
>> Here is a proposal patch. If we are not missing something, the refcnt can be
>> release before call_rcu(). In IPv6, this is already the case.
>>
>> Comments are welcome.
>>
>>
>> Regards,
>> Nicolas
>> pièce jointe différences entre fichiers
>> (0001-ipv4-release-dev-refcnt-early-when-destroying-inetd.patch)
>> From 6fe291ff56b1f94599dfaa57dfb0ed4c168b603f Mon Sep 17 00:00:00 2001
>> From: Nicolas Dichtel <nicolas.dichtel@6wind•com>
>> Date: Fri, 10 Sep 2010 14:52:15 +0200
>> Subject: [PATCH] ipv4: release dev refcnt early when destroying inetdev
>>
>> When a virtual device is removed, refcnt on dev is released
>> after rcu barrier, hence we fall always in the msleep(250)
>> of netdev_wait_allrefs(). This causes a long delay when
>> a lot of interfaces are removed.
>> Refcnt can be released before this rcu barrier, this allows
>> to accelerate the removing of virtual interfaces.
>>
>> Test of removing 50 ipip tunnel interfaces:
>> Before the patch:
>> real 0m12.804s
>> user 0m0.020s
>> sys 0m0.000s
>>
>> After the patch:
>> real 0m0.988s
>> user 0m0.004s
>> sys 0m0.016s
>>
>> Signed-off-by: Wang Xuefu <xuefu.wang@6wind•com>
>> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind•com>
>> ---
>
> This is a well known problem, (many patches were sent some months ago)
> but your patch is not the right solution.
>
> As long as the idev is not yet freed, it can be used and we need to
> access idev->dev
Is this not true in IPv6? What is the difference?
Regards,
Nicolas
next prev parent reply other threads:[~2010-09-10 14:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-10 13:35 [RFC PATCH] ipv4: release dev refcnt early when destroying inetdev Nicolas Dichtel
2010-09-10 14:24 ` Eric Dumazet
2010-09-10 14:57 ` Nicolas Dichtel [this message]
2010-09-10 15:16 ` Eric Dumazet
2010-09-14 20:45 ` David Miller
2010-09-15 6:01 ` Eric Dumazet
2010-09-13 22:24 ` [PATCH] net: use rcu_barrier() in rollback_registered_many Eric Dumazet
2010-09-14 21:27 ` David Miller
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