Periodical interrupt storm when playing game with USB keyboard

[Johannes Lundberg]

Hi all

Some quick dtracing with play causing lag, vs play not causing lag (that is
not hold down any key on a usb keyboard for too long).


# dtrace -n 'profile-997hz /arg0/ { @[func(arg0)]=count(); }'

Lag version
-- snip --
  linuxkpi.ko`idr_find                                              7
  kernel`nanotime                                                   8
  kernel`__cap_rights_init                                          8
  kernel`amd64_syscall                                              8
  i915kms.ko`i915_gem_obj_lookup_or_create_vma                      8
  kernel`selfdfree                                                  9
  kernel`feed_matrix_S16LE                                         11
  kernel`callout_lock                                              11
  kernel`uma_zalloc_arg                                            11
  kernel`z_feed_linear_S16LE                                       12
  kernel`0xffffffff80f6877e                                        12
  kernel`copyin                                                    12
  kernel`tsc_get_timecount_low_lfence                              12
  kernel`bzero                                                     13
  kernel`fget_unlocked                                             14
  i915kms.ko`gen8_ppgtt_insert_pte_entries                         14
  kernel`callout_when                                              16
  kernel`0xffffffff80f68fbc                                        26
  kernel`kern_select                                               32
  kernel`lock_mtx                                                  50
  kernel`spinlock_enter                                            53
  kernel`bcopy                                                     57
  kernel`unlock_mtx                                               104
  i915kms.ko`fw_domains_get                                       113


*  kernel`ukbd_timeout                                             126
kernel`callout_reset_sbt_on                                     128
kernel`ukbd_interrupt                                           136*
*  kernel`softclock_call_cc                                        192*
  kernel`memcpy                                                   284
  kernel`cpu_idle                                                4257

*  kernel`spinlock_exit                                           4312
kernel`lock_delay                                             11921*
  kernel`acpi_cpu_idle                                          15265


No lag version
-- snip --
  kernel`free                                                      19
  kernel`copyout                                                   20
  kernel`copyin                                                    20
  linuxkpi.ko`idr_find                                             21
  kernel`selfdfree                                                 24
  kernel`tsc_get_timecount_low_lfence                              25
  kernel`__mtx_lock_flags                                          28
  kernel`uma_zalloc_arg                                            30
  kernel`bzero                                                     31
  i915kms.ko`gen8_ppgtt_insert_entries                             31
  drm.ko`drm_ioctl                                                 32
  kernel`fget_unlocked                                             36
  kernel`amd64_syscall                                             37
  kernel`kern_select                                               49
  i915kms.ko`gen8_ppgtt_insert_pte_entries                         61
  kernel`0xffffffff80f68fbc                                        78
  kernel`bcopy                                                     90
  i915kms.ko`fw_domains_get                                       228
  kernel`spinlock_exit                                            284
  kernel`cpu_idle                                                4698
  kernel`acpi_cpu_idle                                          36288


I also tried rebuilding linux-c6_sdl-1.2 using get time functions in librt
vs libc but no difference.
Will dig deeper next time I have free time to spare.



On Tue, Jan 23, 2018 at 2:33 AM, blubee blubeeme <gurenchan at gmail.com>
wrote:

>
>
> On Tue, Jan 23, 2018 at 9:48 AM, Adrian Chadd <adrian.chadd at gmail.com>
> wrote:
>
>> Hi
>>
>> Yeah the timers eventually get coalesced unless someone's asking for a
>> ridciulously accurate timer value.
>>
>> So is some driver asking for hyper-accurate callout timer that isn't
>> being coalesced? hps, is there any useful debugging to try and find
>> callouts that are requesting stupidly accurate timers? Maybe a dtrace
>> probe on the callout schedule entry point?
>>
>>
>>
>> -adrian
>> _______________________________________________
>> freebsd-current at freebsd.org mailing list
>> https://lists.freebsd.org/mailman/listinfo/freebsd-current
>> To unsubscribe, send any mail to "freebsd-current-unsubscribe at freebsd.org
>> "
>>
> I'd say dtrace might be able to get you in the right direction very
> quickly.
>
> I used SDL in the past for android apps and the code is very Linux
> specific. I am sure there's some Linux related timers in there somewhere
> that FreeBSD is returning nothing from and that's what's killing the
> performance.
>
> I can almost guarantee that none of the SDL designers and or programmers
> use any *BSD systems.
>
> The easiest solution would be to go look at the timer code and implement
> something that FreeBSD can work with and try to get that upstream.
>
> These are just a few of the issues that will crop up when devs try to just
> use shims to hook into the Linux kernel. Do the design work up front and
> implement things in a native way or enjoy the jank.
>
> DTrace should be able to point you in the right direction relatively
> quickly.
> The DTraceBook: https://www.amazon.com/DTrace-Dynamic-
> Tracing-Solaris-FreeBSD/dp/0132091518
>
> Best
>