1. 24 6月, 2009 1 次提交
    • H
      timer stats: Optimize by adding quick check to avoid function calls · 507e1231
      Heiko Carstens 提交于
      When the kernel is configured with CONFIG_TIMER_STATS but timer
      stats are runtime disabled we still get calls to
      __timer_stats_timer_set_start_info which initializes some
      fields in the corresponding struct timer_list.
      
      So add some quick checks in the the timer stats setup functions
      to avoid function calls to __timer_stats_timer_set_start_info
      when timer stats are disabled.
      
      In an artificial workload that does nothing but playing ping
      pong with a single tcp packet via loopback this decreases cpu
      consumption by 1 - 1.5%.
      
      This is part of a modified function trace output on SLES11:
      
       perl-2497  [00] 28630647177732388 [+  125]: sk_reset_timer <-tcp_v4_rcv
       perl-2497  [00] 28630647177732513 [+  125]: mod_timer <-sk_reset_timer
       perl-2497  [00] 28630647177732638 [+  125]: __timer_stats_timer_set_start_info <-mod_timer
       perl-2497  [00] 28630647177732763 [+  125]: __mod_timer <-mod_timer
       perl-2497  [00] 28630647177732888 [+  125]: __timer_stats_timer_set_start_info <-__mod_timer
       perl-2497  [00] 28630647177733013 [+   93]: lock_timer_base <-__mod_timer
      Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Mustafa Mesanovic <mustafa.mesanovic@de.ibm.com>
      Cc: Arjan van de Ven <arjan@infradead.org>
      LKML-Reference: <20090623153811.GA4641@osiris.boeblingen.de.ibm.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      507e1231
  2. 23 6月, 2009 39 次提交