Messages in this thread |  | | | Date | Fri, 9 May 2008 00:02:29 +0200 | | From | Ingo Molnar <> | | Subject | Re: [patch] speed up / fix the new generic semaphore code (fix AIM7 40% regression with 2.6.26-rc1) |
| |
* Ingo Molnar <mingo@elte.hu> wrote:
> yeah, i captured a trace of all the down()s that happen in the > workload, using ftrace/sched_switch + stacktrace + a tracepoint in > down(). Here's the semaphore activities in the trace:
i've updated the trace with a better one:
> http://redhat.com/~mingo/misc/aim7-ftrace.txt
the first one had some idle time in it as well plus the effects of a 2000-task Ctrl-Z - which skewed the histograms.
the new stats are more straightforward. down() callsite histogram:
42 down <= lock_kernel <= de_put <= proc_delete_inode < 42 down <= lock_kernel <= proc_lookup_de <= proc_lookup < 78 down <= lock_kernel <= proc_lookup_de <= proc_lookup < 310 down <= lock_kernel <= sys_fcntl <= system_call_after_swapgs < 332 down <= lock_kernel <= vfs_ioctl <= do_vfs_ioctl < 380 down <= lock_kernel <= tty_release <= __fput < 422 down <= lock_kernel <= chrdev_open <= __dentry_open <
hm, why is chrdev_open() called all that often?
top-5 wakeups:
4 default_wake_function <= __wake_up_common <= complete <= migration_thread <= kthread <= child_rip < 4 wake_up_process <= sched_exec <= do_execve <= sys_execve <= stub_execve <= < 8 wake_up_process <= __mutex_unlock_slowpath <= mutex_unlock <= do_filp_open <= do_sys_open <= sys_open < 40 default_wake_function <= autoremove_wake_function <= __wake_up_common <= __wake_up <= sock_def_wakeup <= tcp_rcv_state_process < 98 default_wake_function <= __wake_up_common <= __wake_up_sync <= do_notify_parent <= do_exit <= do_group_exit <
i.e. very little wakeup activities. Top 10 scheduling points:
10 schedule <= kjournald <= kthread <= child_rip < 12 schedule <= __down_write_nested <= __down_write <= down_write < 29 schedule <= worker_thread <= kthread <= child_rip < 40 schedule <= schedule_timeout <= inet_stream_connect <= sys_connect < 59 schedule <= __cond_resched <= _cond_resched <= generic_file_buffered_write < 111 schedule <= ksoftirqd <= kthread <= child_rip < 119 schedule <= do_wait <= sys_wait4 <= system_call_after_swapgs < 659 schedule <= do_exit <= do_group_exit <= sys_exit_group < 781 schedule <= sysret_careful <= <= 0 < 1347 schedule <= retint_careful <= <= 0 <
> and here's a few seconds worth of NMI driven readprofile output:
the NMI profiling results were accurate.
Ingo
|  |