Re: 2.6.25-rc3-mm1 - PROFILE_LIKELY redux..

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 05 Mar 2008 17:26:25 -0500
Valdis.Kletnieks@vt.edu wrote:

> On Wed, 05 Mar 2008 10:02:21 PST, Andrew Morton said:
> 
> > at the top, so it'll be something else.  Perhaps a `likely' snuck in via an
> > inline in a header file.  It would be better to add a #define DONT_DO_THAT
> > at the top of arch/x86/kernel/vsyscall_64.c and
> > arch/x86/vdso/vclock_gettime.c, then use that to defeat likely-profiling.
> > 
> >  arch/x86/kernel/vsyscall_64.c  |   11 ++---------
> >  arch/x86/vdso/vclock_gettime.c |   11 ++---------
> >  include/linux/compiler.h       |    3 ++-
> >  3 files changed, 6 insertions(+), 19 deletions(-)
> 
> Confirming that this patch works and my system goes multi-user cleanly.

Thanks.

> Actual numbers after about 10 minutes of uptime:
> 
> % wc -l /proc/likely_prof 
> 2635 /proc/likely_prof
> % grep '^[^ ]' /proc/likely_prof 
> Likely Profiling Results
> [+- ] Type | # True | # False | Function:Filename@Line
> +unlikely |        1|        0  in_dev_get()@:include/linux/inetdevice.h@185
> +unlikely |      513|        0  dst_input()@:include/net/dst.h@254
> -likely   |        0|      148  ip6_mc_input()@:net/ipv6/ip6_input.c@271
> -likely   |        0|        1  sock_error()@:include/net/sock.h@1211
> -likely   |      851|     1219  tcp_transmit_skb()@:net/ipv4/tcp_output.c@493
> +unlikely |        1|        0  signal_pending()@:include/linux/sched.h@1927
> -likely   |        0|  1172946  audit_syscall_entry()@:kernel/auditsc.c@1522
> +unlikely |  1172716|        0  syscall_trace_enter()@:arch/x86/kernel/ptrace.c@1556
> -likely   |        0|  1173020  audit_syscall_exit()@:kernel/auditsc.c@1551
> +unlikely |  1172831|        0  syscall_trace_leave()@:arch/x86/kernel/ptrace.c@1573
> -likely   |        0|     1272  audit_alloc()@:kernel/auditsc.c@841
> +unlikely |        3|        0  icmp_unreach()@:net/ipv4/icmp.c@773
> +unlikely |        2|        1  nf_ct_attach()@:net/netfilter/core.c@230
> -likely   |        0|        2  dst_gc_task()@:net/core/dst.c@82
> +unlikely |      143|       61  fput_light()@:include/linux/file.h@77
> +unlikely |      892|      424  _read_unlock_irqrestore()@:kernel/spinlock.c@375
> +unlikely |       28|        0  sched_move_task()@:kernel/sched.c@7835
> +unlikely |       28|        0  sched_move_task()@:kernel/sched.c@7828
> +unlikely |      108|        0  verify_export_symbols()@:kernel/module.c@1401
> +unlikely |      313|        0  verify_export_symbols()@:kernel/module.c@1393
> +unlikely |       14|        0  ll_front_merge_fn()@:block/blk-merge.c@347
> -likely   |       17|     1150  audit_free()@:kernel/auditsc.c@1428
> -likely   |       17|  1174290  audit_get_context()@:kernel/auditsc.c@711
> +unlikely |       33|        0  inotify_find_update_watch()@:fs/inotify.c@591
> +unlikely |     4360|      775  kill_pid_info()@:kernel/signal.c@1065
> +unlikely |     7239|     2767  next_pidmap()@:kernel/pid.c@194
> +unlikely |    42009|    33683  copy_pte_range()@:mm/memory.c@510
> -likely   |        0|        1  qh_completions()@:drivers/usb/host/ehci-q.c@368
> +unlikely |    19934|        0  ll_back_merge_fn()@:block/blk-merge.c@309
> -likely   |      927|     2323  load_elf_binary()@:fs/binfmt_elf.c@896
> +unlikely |     2435|      875  pmd_alloc()@:include/linux/mm.h@862
> +unlikely |       13|       12  psmouse_interrupt()@:drivers/input/mouse/psmouse-base.c@296
> +unlikely |       70|       25  psmouse_interrupt()@:drivers/input/mouse/psmouse-base.c@292
> -likely   |       20|       80  qh_completions()@:drivers/usb/host/ehci-q.c@415
> -likely   |        0|       30  qh_completions()@:drivers/usb/host/ehci-q.c@319
> -likely   |        5|       14  submit_async()@:drivers/usb/host/ehci-q.c@975
> +unlikely |       19|        2  qh_append_tds()@:drivers/usb/host/ehci-q.c@876
> -likely   |        6|       15  atapi_drain_needed()@:drivers/ata/libata-scsi.c@846
> +unlikely |    27395|    18153  add_timer_randomness()@:drivers/char/random.c@628
> +unlikely |    34665|    19948  bio_phys_segments()@:fs/bio.c@226
> -likely   |      347|      678  clocksource_adjust()@:kernel/time/timekeeping.c@418
> -likely   |        1|        4  __ata_qc_from_tag()@:include/linux/libata.h@1319
> -likely   |        0|       15  __cancel_work_timer()@:kernel/workqueue.c@490
> +unlikely |    15638|     1127  queue_delayed_work_on()@:kernel/workqueue.c@233
> +unlikely |        2|        0  srcu_notifier_chain_register()@:kernel/notifier.c@419
> +unlikely |     6502|     2429  queue_work()@:kernel/workqueue.c@171
> +unlikely |        9|        2  blocking_notifier_chain_register()@:kernel/notifier.c@212
> +unlikely |    13631|        0  pre_schedule_rt()@:kernel/sched_rt.c@961
> +unlikely |   591400|   443725  __update_curr()@:kernel/sched_fair.c@313
> +unlikely |   233625|   205658  __switch_to()@:arch/x86/kernel/process_64.c@656
> +unlikely |   313057|   126225  __switch_to()@:arch/x86/kernel/process_64.c@641
> +unlikely |   313053|   126225  __switch_to()@:arch/x86/kernel/process_64.c@637
> +unlikely |   467383|        0  sched_info_switch()@:kernel/sched_stats.h@230
> +unlikely |   188448|    13628  pick_next_task_rt()@:kernel/sched_rt.c@522
> +unlikely |   240619|        0  sched_info_queued()@:kernel/sched_stats.h@188
> -likely   |       61|      644  ifind()@:fs/inode.c@798
> +unlikely |   258562|    61703  scheduler_tick()@:kernel/sched.c@3756
> -likely   |    61220|   241529  acct_update_integrals()@:kernel/tsacct.c@120
> +unlikely |  1189922|   902477  kfree()@:mm/slab.c@3785
> +unlikely |       23|        0  __rmqueue_fallback()@:mm/page_alloc.c@812
> +unlikely |    14376|     9655  rt_policy()@:kernel/sched.c@140

These are all the ones which we got wrong on your setup, yes?

I wonder if assuming that current->audit_context is NULL is realistic
nowadays.