netdev - Re: [PATCH net-next-2.6] net: add dev_close

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1292259145.2759.55.camel@edumazet-laptop>
Date:	Mon, 13 Dec 2010 17:52:25 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Octavian Purdila <opurdila@...acom.com>
Cc:	netdev@...r.kernel.org,
	Lucian Adrian Grijincu <lucian.grijincu@...il.com>,
	Vlad Dogaru <ddvlad@...edu.org>
Subject: Re: [PATCH net-next-2.6] net: add dev_close_many

Le lundi 13 décembre 2010 à 16:18 +0200, Octavian Purdila a écrit :
> Add dev_close_many and dev_deactivate_many to factorize another
> expensive sync-rcu operation in the netdevice unregister path.
> 
> $ modprobe dummy numdummies=10000
> $ ip link set dev dummy* up
> $ time rmmod dummy
> 
> Without the patch           With the patch
> 
> real    0m 24.63s           real    0m 5.15s
> user    0m 0.00s            user    0m 0.00s
> sys     0m 6.05s            sys     0m 5.14s
> 
> Signed-off-by: Octavian Purdila <opurdila@...acom.com>
> ---

Hmm, I think this solves the "rmmod dummy" case, but not the "dismantle
devices one by one", which is the general one (on heavy duty tunnels/ppp
servers)

I think we could use a kernel thread (a workqueue presumably), handling
3 lists of devices to be dismantled, respecting one rcu grace period (or
rcu_barrier()) before transfert of one item from one list to following
one.

This way, each device removal could post a device to this kernel thread
and return to user immediately. Time of RTNL hold would be reduced
(calls to synchronize_rcu() would be done with RTNL not held)



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html