linux-kernel - Re: getaddrinfo slowdown in 3.17.1, due to getifaddrs

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Message-ID: <20141018104525.GA15789@sesse.net>
Date:	Sat, 18 Oct 2014 12:45:25 +0200
From:	"Steinar H. Gunderson" <sgunderson@...foot.com>
To:	linux-kernel@...r.kernel.org
Cc:	Thomas Graf <tgraf@...g.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Nikolay Aleksandrov <nikolay@...hat.com>
Subject: Re: getaddrinfo slowdown in 3.17.1, due to getifaddrs

On Fri, Oct 17, 2014 at 02:34:30AM +0200, Steinar H. Gunderson wrote:
> e341694e3eb57fcda9f1adc7bfea42fe080d8d7a looks like it might cause something
> like this (it certainly added the synchronize_net() call). Cc-ing people on 
> that commit; quoting the entire rest of the message for reference.

I see there's discussion on what to do with this; thanks. :-)

FWIW, I've verified that reverting these four patches (in that order) fixes
the problem:

  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/patch/net/netlink/af_netlink.c?id=9ce12eb16ffb143f3a509da86283ddd0b10bcdb3
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/patch/net/netlink/af_netlink.c?id=6c8f7e70837468da4e658080d4448930fb597e1b
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/patch/net/netlink/af_netlink.c?id=67a24ac18b0262178ba9f05501b2c6e6731d449a
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/patch/net/netlink/af_netlink.c?id=e341694e3eb57fcda9f1adc7bfea42fe080d8d7a

My Perl script is seemingly not the only affected program on the system;
witness the average page load times for our PHP-based home page:

  http://home.samfundet.no/~sesse/web_load_time_samfundet_no-week.png

/* Steinar */
-- 
Homepage: http://www.sesse.net/
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