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From: Stephen Hemminger <stephen@networkplumber.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>,
	tglx@linutronix.de, a.darwish@linutronix.de,
	peterz@infradead.org, mingo@redhat.com, will@kernel.org,
	paulmck@kernel.org, bigeasy@linutronix.de, rostedt@goodmis.org,
	linux-kernel@vger.kernel.org, kuba@kernel.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH v1 01/25] net: core: device_rename: Use rwsem instead of a seqcount
Date: Tue, 19 May 2020 21:36:37 -0700
Message-ID: <20200519213637.4d874aad@hermes.lan> (raw)
In-Reply-To: <886041df-d889-3d88-59fe-e190d15f9c98@gmail.com>

On Tue, 19 May 2020 20:18:19 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> On 5/19/20 7:57 PM, David Miller wrote:
> > From: Thomas Gleixner <tglx@linutronix.de>
> > Date: Wed, 20 May 2020 01:42:30 +0200
> >   
> >> Stephen Hemminger <stephen@networkplumber.org> writes:  
> >>> On Wed, 20 May 2020 00:23:48 +0200
> >>> Thomas Gleixner <tglx@linutronix.de> wrote:  
> >>>> No. We did not. -ENOTESTCASE  
> >>>
> >>> Please try, it isn't that hard..
> >>>
> >>> # time for ((i=0;i<1000;i++)); do ip li add dev dummy$i type dummy; done
> >>>
> >>> real	0m17.002s
> >>> user	0m1.064s
> >>> sys	0m0.375s  
> >>
> >> And that solves the incorrectness of the current code in which way?  
> > 
> > You mentioned that there wasn't a test case, he gave you one to try.
> >   
> 
> I do not think this would ever use device rename, nor netdev_get_name()
> 
> None of this stuff is fast path really.
> 
> # time for ((i=1;i<1000;i++)); do ip li add dev dummy$i type dummy; done
> 
> real	0m1.127s
> user	0m0.270s
> sys	0m1.039s

Your right it is a weak test, and most of the overhead is in the syscall
and all netlink events that happen.

It does end up looking up the new name, so would exercise that.
Better test is to use %d syntax or create 1000 dummy's then rename every one.

This is more of a stress test
# for ((i=0;i<1000;i++)); do echo link add dev dummy%d type dummy; done | time ip -batch -
0.00user 0.29system 0:02.11elapsed 13%CPU (0avgtext+0avgdata 2544maxresident)k
0inputs+0outputs (0major+148minor)pagefaults 0swaps

# for ((i=999;i>=0;i--)); do echo link set dummy$i name dummy$((i+1)); done | time ip -batch -
0.00user 0.26system 0:54.98elapsed 0%CPU (0avgtext+0avgdata 2508maxresident)k
0inputs+0outputs (0major+145minor)pagefaults 0swaps


  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 21:45 [PATCH v1 00/25] seqlock: Extend seqcount API with associated locks Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 01/25] net: core: device_rename: Use rwsem instead of a seqcount Ahmed S. Darwish
2020-05-19 22:01   ` Stephen Hemminger
2020-05-19 22:23     ` Thomas Gleixner
2020-05-19 23:11       ` Stephen Hemminger
2020-05-19 23:42         ` Thomas Gleixner
2020-05-20  0:06           ` Stephen Hemminger
2020-05-20  1:55             ` Thomas Gleixner
2020-05-20  2:57           ` David Miller
2020-05-20  3:18             ` Eric Dumazet
2020-05-20  4:36               ` Stephen Hemminger [this message]
2020-05-20 19:37             ` Thomas Gleixner
2020-05-20 21:36               ` Stephen Hemminger
2020-05-20  2:01   ` Eric Dumazet
2020-05-20  6:42     ` Ahmed S. Darwish
2020-05-20 12:51       ` Eric Dumazet
2020-06-03 14:33         ` Ahmed S. Darwish
2020-05-20 14:37   ` Dan Carpenter
2020-05-25 16:22     ` Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 03/25] net: phy: fixed_phy: Remove unused seqcount Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 05/25] u64_stats: Document writer non-preemptibility requirement Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 15/25] netfilter: conntrack: Use sequence counter with associated spinlock Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 16/25] netfilter: nft_set_rbtree: Use sequence counter with associated rwlock Ahmed S. Darwish
2020-05-19 21:45 ` [PATCH v1 17/25] xfrm: policy: Use sequence counters with associated lock Ahmed S. Darwish
2020-06-08  0:57 ` [PATCH v2 00/18] seqlock: Extend seqcount API with associated locks Ahmed S. Darwish
2020-06-08  0:57   ` [PATCH v2 08/18] netfilter: conntrack: Use sequence counter with associated spinlock Ahmed S. Darwish
2020-06-08  0:57   ` [PATCH v2 09/18] netfilter: nft_set_rbtree: Use sequence counter with associated rwlock Ahmed S. Darwish
2020-06-08  0:57   ` [PATCH v2 10/18] xfrm: policy: Use sequence counters with associated lock Ahmed S. Darwish
2020-06-30  5:44 ` [PATCH v3 00/20] seqlock: Extend seqcount API with associated locks Ahmed S. Darwish
2020-06-30  5:44   ` [PATCH v3 10/20] netfilter: conntrack: Use sequence counter with associated spinlock Ahmed S. Darwish
2020-06-30  5:44   ` [PATCH v3 11/20] netfilter: nft_set_rbtree: Use sequence counter with associated rwlock Ahmed S. Darwish
2020-06-30  5:44   ` [PATCH v3 12/20] xfrm: policy: Use sequence counters with associated lock Ahmed S. Darwish
2020-07-20 15:55 ` [PATCH v4 00/24] seqlock: Extend seqcount API with associated locks Ahmed S. Darwish
2020-07-20 15:55   ` [PATCH v4 14/24] netfilter: conntrack: Use sequence counter with associated spinlock Ahmed S. Darwish
2020-07-20 15:55   ` [PATCH v4 15/24] netfilter: nft_set_rbtree: Use sequence counter with associated rwlock Ahmed S. Darwish
2020-07-20 15:55   ` [PATCH v4 16/24] xfrm: policy: Use sequence counters with associated lock Ahmed S. Darwish
2020-07-20 16:49   ` [PATCH v4 00/24] seqlock: Extend seqcount API with associated locks Eric Biggers
2020-07-20 17:33     ` Ahmed S. Darwish

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