netdev - Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3)

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Message-ID: <20151102062240.GQ22011@ZenIV.linux.org.uk>
Date:	Mon, 2 Nov 2015 06:22:40 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Network Development <netdev@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect
 for sockets in accept(3)

On Sun, Nov 01, 2015 at 06:14:43PM -0800, Eric Dumazet wrote:
> On Mon, 2015-11-02 at 00:24 +0000, Al Viro wrote:
> 
> > This ought to be a bit cleaner.  Eric, could you test the variant below on your
> > setup?
> 
> Sure !
> 
> 5 runs of :
> lpaa24:~# taskset ff0ff ./opensock -t 16 -n 10000000 -l 10
> 
> total = 4386311
> total = 4560402
> total = 4437309
> total = 4516227
> total = 4478778

Umm...  With Linus' variant it was what, around 4000000?  +10% or so, then...

> With 48 threads :
> 
> ./opensock -t 48 -n 10000000 -l 10
> total = 4940245
> total = 4848513
> total = 4813153
> total = 4813946
> total = 5127804

And that - +40%?  Interesting...  And it looks like at 48 threads you are
still seeing arseloads of contention, but apparently less than with Linus'
variant...  What if you throw the __clear_close_on_exec() patch on
top of that?

Looks like it's spending less time under ->files_lock...  Could you get
information on fs/file.o hotspots?
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