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From: David Laight <David.Laight@ACULAB.COM>
To: 'Alexander Duyck' <alexander.h.duyck@intel.com>,
	Tom Herbert <therbert@google.com>
Cc: David Miller <davem@davemloft.net>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Linux Netdev List <netdev@vger.kernel.org>,
	Rick Jones <rick.jones2@hp.com>
Subject: RE: Performance regression on kernels 3.10 and newer
Date: Mon, 18 Aug 2014 09:03:21 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1747969E@AcuExch.aculab.com> (raw)
In-Reply-To: <53EE967F.9090101@intel.com>

From: Alexander Duyck
> ...
> Another test I tried was to hack the nettest_bsd.c file in netperf to
> perform a poll() based receive.  That resolved the issue and had all the
> performance of the tcp_low_latency case.  I may see if I can work with
> Rick to push something like that into netperf as I really would prefer
> to avoid having to advise everyone on how to setup the sysctl for
> tcp_low_latency.

Doesn't that generate 2 system calls per receive?
Unless it now returns more data per receive I'm surprised that
it actually faster.

OTOH I've some code that runs a lot better when I run while :; do :; done
for all but one of the cpus.
I think that is because the processes spinning in userspace don't
get pre-empted.

	David


  reply	other threads:[~2014-08-18  9:04 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-14 18:19 Performance regression on kernels 3.10 and newer Alexander Duyck
2014-08-14 18:46 ` Eric Dumazet
2014-08-14 19:50   ` Eric Dumazet
2014-08-14 19:59   ` Rick Jones
2014-08-14 20:31     ` Alexander Duyck
2014-08-14 20:51       ` Eric Dumazet
2014-08-14 20:46     ` Eric Dumazet
2014-08-14 23:16   ` Alexander Duyck
2014-08-14 23:20     ` David Miller
2014-08-14 23:25       ` Tom Herbert
2014-08-21 23:24         ` David Miller
2014-09-06 14:45           ` Eric Dumazet
2014-09-06 15:27             ` Eric Dumazet
2014-09-06 15:46               ` Eric Dumazet
2014-09-06 16:38                 ` Eric Dumazet
2014-09-06 18:21                   ` Eric Dumazet
2014-09-07 19:05                     ` [PATCH net] ipv6: refresh rt6i_genid in ip6_pol_route() Eric Dumazet
2014-09-07 22:54                       ` David Miller
2014-09-08  4:18                         ` Eric Dumazet
2014-09-08  4:27                           ` David Miller
2014-09-08  4:43                             ` Eric Dumazet
2014-09-08  4:59                               ` David Miller
2014-09-08  5:07                                 ` Eric Dumazet
2014-09-08  8:11                                   ` Nicolas Dichtel
2014-09-08 10:28                                     ` Eric Dumazet
2014-09-08 12:16                                       ` Nicolas Dichtel
2014-09-08 18:48                                   ` Vlad Yasevich
2014-09-09 12:58                                   ` Hannes Frederic Sowa
2014-09-10  9:31                                     ` [PATCH net-next] ipv6: implement rt_genid_bump_ipv6 with fn_sernum and remove rt6i_genid Hannes Frederic Sowa
2014-09-10 13:26                                       ` Vlad Yasevich
2014-09-10 13:42                                         ` Hannes Frederic Sowa
2014-09-10 20:09                                       ` David Miller
2014-09-11  8:30                                         ` Hannes Frederic Sowa
2014-09-11 12:22                                           ` Vlad Yasevich
2014-09-11 12:40                                             ` Hannes Frederic Sowa
2014-09-11 12:05                                         ` Hannes Frederic Sowa
2014-09-11 14:19                                           ` Vlad Yasevich
2014-09-11 14:32                                             ` Hannes Frederic Sowa
2014-09-11 14:44                                               ` Vlad Yasevich
2014-09-11 14:47                                                 ` Hannes Frederic Sowa
2014-09-08 15:06               ` [PATCH v2 net-next] tcp: remove dst refcount false sharing for prequeue mode Eric Dumazet
2014-09-08 21:21                 ` David Miller
2014-09-08 21:30                   ` Eric Dumazet
2014-09-08 22:41                     ` David Miller
2014-09-09 23:56                     ` David Miller
2014-08-15 17:15       ` Performance regression on kernels 3.10 and newer Alexander Duyck
2014-08-15 17:59         ` Eric Dumazet
2014-08-15 18:49         ` Tom Herbert
2014-08-15 19:10           ` Alexander Duyck
2014-08-15 22:16             ` Tom Herbert
2014-08-15 23:23               ` Alexander Duyck
2014-08-18  9:03                 ` David Laight [this message]
2014-08-18 15:22                   ` Alexander Duyck
2014-08-18 15:29                     ` Rick Jones
2014-08-21 23:51         ` David Miller
2014-08-14 23:48     ` Eric Dumazet
2014-08-15  0:33       ` Rick Jones

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