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  1. Mar 09, 2011
    • Jiri Olsa's avatar
      x86: Separate out entry text section · ea714547
      Jiri Olsa authored
      
      
      Put x86 entry code into a separate link section: .entry.text.
      
      Separating the entry text section seems to have performance
      benefits - caused by more efficient instruction cache usage.
      
      Running hackbench with perf stat --repeat showed that the change
      compresses the icache footprint. The icache load miss rate went
      down by about 15%:
      
       before patch:
               19417627  L1-icache-load-misses      ( +-   0.147% )
      
       after patch:
               16490788  L1-icache-load-misses      ( +-   0.180% )
      
      The motivation of the patch was to fix a particular kprobes
      bug that relates to the entry text section, the performance
      advantage was discovered accidentally.
      
      Whole perf output follows:
      
       - results for current tip tree:
      
        Performance counter stats for './hackbench/hackbench 10' (500 runs):
      
               19417627  L1-icache-load-misses      ( +-   0.147% )
             2676914223  instructions             #      0.497 IPC     ( +- 0.079% )
             5389516026  cycles                     ( +-   0.144% )
      
            0.206267711  seconds time elapsed   ( +-   0.138% )
      
       - results for current tip tree with the patch applied:
      
        Performance counter stats for './hackbench/hackbench 10' (500 runs):
      
               16490788  L1-icache-load-misses      ( +-   0.180% )
             2717734941  instructions             #      0.502 IPC     ( +- 0.079% )
             5414756975  cycles                     ( +-   0.148% )
      
            0.206747566  seconds time elapsed   ( +-   0.137% )
      
      Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Nick Piggin <npiggin@kernel.dk>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: masami.hiramatsu.pt@hitachi.com
      Cc: ananth@in.ibm.com
      Cc: davem@davemloft.net
      Cc: 2nddept-manager@sdl.hitachi.co.jp
      LKML-Reference: <20110307181039.GB15197@jolsa.redhat.com>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      ea714547
    • Ingo Molnar's avatar
      Merge commit 'v2.6.38-rc8' into perf/core · 86cb2ec7
      Ingo Molnar authored
      
      
      Merge reason: Merge latest fixes.
      
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      86cb2ec7
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