Message-Id: <20090512040832.681953177@goodmis.org>
Date:	Tue, 12 May 2009 00:08:32 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 0/5] [GIT PULL] ring-buffer: optimize to 17% performance increase


Ingo,

This patch series tunes the ring buffer to be a bit faster. I used
the ring-buffer-benmark test to help give a good idea on the
performance of the buffer. I ran it on an 2.8 GHz 4way box on an
idle system. I only wanted to test the write without the reader, since
the reader can produce some cacheline bouncing. To do this I inserted
the benchmark module with the "disable_reader=1" option.

Note, when I disable the ring buffer and run the test, I get an average
of 87 ns. Thus the overhead of the test is 87ns, and I will show both
the full time and the 87 subtracted from the time (in parenthesis).

I'm also including the size of the ring_buffer.o object since some changes
helped in shrinking the text segments too.

Before the patch series:

benchmark:  307 ns (220 ns)
   text    data     bss     dec     hex filename
  16554      24      12   16590    40ce kernel/trace/ring_buffer.o
          
         
commit 1cd8d7358948909ab80b254eb14bcebc555ad417
ring-buffer: remove type parameter from rb_reserve_next_event
             
benchmark: 302 ns (215 ns)
   text    data     bss     dec     hex filename
  16538      24      12   16574    40be kernel/trace/ring_buffer.o
    
commit be957c447f7233a67904a1b11eb3ab61e702bf4d
ring-buffer: move calculation of event length

benchmark: 293 ns (206 ns)
   text    data     bss     dec     hex filename
  16490      24      12   16526    408e kernel/trace/ring_buffer.o
    
commit 0f0c85fc80adbbd2265d89867d743f929d516805
ring-buffer: small optimizations

benchmark: 285 ns (198 ns)
   text    data     bss     dec     hex filename
  16474      24      12   16510    407e kernel/trace/ring_buffer.o

commit 88eb0125362f2ab272cbaf84252cf101ddc2dec9
ring-buffer: use internal time stamp function

benchmark: 282 ns (195 ns)
   text    data     bss     dec     hex filename
  16474      24      12   16510    407e kernel/trace/ring_buffer.o


commit 168b6b1d0594c7866caa73b12f3b8d91075695f2
ring-buffer: move code around to remove some branches

benchmark: 270 ns (183 ns)
   text    data     bss     dec     hex filename
  16490      24      12   16526    408e kernel/trace/ring_buffer.o

Thus we went from an average of 220 ns per recording, to 183 ns.
Which is about a 17% performance gain.

For your information:

Adding a reader that reads via pages (like splice), the time jumps to
326 ns.

Adding a reader that reades event by event it jumps to (with lots
of overruns)
469 ns.

But disabling the ring buffer, the overhead for the test jumps from 87 ns
to 113 ns, making the ring buffer cost with busy reader: 213 ns and 356 ns.

Please pull the latest tip/tracing/ftrace tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/ftrace


Steven Rostedt (5):
      ring-buffer: remove type parameter from rb_reserve_next_event
      ring-buffer: move calculation of event length
      ring-buffer: small optimizations
      ring-buffer: use internal time stamp function
      ring-buffer: move code around to remove some branches

----
 kernel/trace/ring_buffer.c |   63 +++++++++++++++++++++++++-------------------
 1 files changed, 36 insertions(+), 27 deletions(-)
-- 
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