Re: [PATCH V12 2/4] drivers/perf: imx_ddr: Add ddr performance counter support

[Will Deacon <will.deacon@arm.com>]

On Tue, Jun 18, 2019 at 12:24:19PM -0500, Zhi Li wrote:
> On Fri, Jun 14, 2019 at 5:23 AM Will Deacon <will.deacon@arm.com> wrote:
> >
> > On Thu, Jun 13, 2019 at 02:13:20PM -0500, Zhi Li wrote:
> > > On Thu, Jun 13, 2019 at 12:44 PM Will Deacon <will.deacon@arm.com> wrote:
> > > >
> > > > On Thu, Jun 13, 2019 at 12:04:37PM -0500, Zhi Li wrote:
> > > > > On Thu, Jun 13, 2019 at 6:23 AM Will Deacon <will.deacon@arm.com> wrote:
> > > > > >
> > > > > > On Wed, May 01, 2019 at 06:43:29PM +0000, Frank Li wrote:
> > > > > > > Add ddr performance monitor support for iMX8QXP
> > > > > > >
> > > > > > > There are 4 counters for ddr perfomance events.
> > > > > > > counter 0 is dedicated for cycles.
> > > > > > > you choose any up to 3 no cycles events.
> > > > > > >
> > > > > > > for example:
> > > > > > >
> > > > > > > perf stat -a -e imx8_ddr0/read-cycles/,imx8_ddr0/write-cycles/,imx8_ddr0/precharge/ ls
> > > > > > > perf stat -a -e imx8_ddr0/cycles/,imx8_ddr0/read-access/,imx8_ddr0/write-access/ ls
> > > > > >
> > > > > > I've pushed patches 1, 2 and 4 out with some minor tweaks to:
> > > > > >
> > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=for-next/perf
> > > > > >
> > > > > > I'll leave the actual .dts change to go via the soc tree, since last time
> > > > > > I took one of those it just resulted in conflicts.
> > > > > >
> > > > > > Frank, Andrey: Please could you try to run the perf fuzzer on this before
> > > > > > it lands in mainline? It has a good track record of finding nasty PMU driver
> > > > > > bugs, but it obviously requires access to hardware which implements the PMU:
> > > > > >
> > > > > > http://web.eece.maine.edu/~vweaver/projects/perf_events/fuzzer/
> > > > >
> > > > > Okay, how long should be run generally?
> > > > > I need make sure it can pass without my patches at our platform.
> > > >
> > > > As you long as you can really, but if it survives a few hours that's usually
> > > > a good sign. Overnight is even better.
> > >
> > > Base on commit f2c7c76c5d0a443053e94adb9f0918fa2fb85c3a
> > > Author: Linus Torvalds <torvalds@linux-foundation.org>
> > > Date:   Sun Jun 2 13:55:33 2019 -0700
> > >
> > >     Linux 5.2-rc3
> > >
> > > RCU report problem:
> > >
> > > [ 6048.741784] rcu: INFO: rcu_preempt self-detected stall on CPU
> > > [ 6048.747550] rcu:     1-....: (5249 ticks this GP)
> > > idle=c5a/1/0x4000000000000004 softirq=503121/503121 fqs=2425
> > > [ 6048.757384]  (t=5253 jiffies g=1416105 q=117)
> > > [ 6048.761745] Task dump for CPU 1:
> > > [ 6048.764977] perf_fuzzer     R  running task        0 32520    426 0x00000202
> > > [ 6048.772030] Call trace:
> > > [ 6048.774493]  dump_backtrace+0x0/0x130
> > > [ 6048.778159]  show_stack+0x14/0x20
> > > [ 6048.781477]  sched_show_task+0x108/0x138
> > > [ 6048.785401]  dump_cpu_task+0x40/0x4c
> > > [ 6048.788983]  rcu_dump_cpu_stacks+0x94/0xd0
> > > [ 6048.793082]  rcu_sched_clock_irq+0x5e0/0x918
> > > [ 6048.797357]  update_process_times+0x2c/0x70
> > > [ 6048.801545]  tick_sched_handle.isra.6+0x3c/0x50
> > > [ 6048.806076]  tick_sched_timer+0x48/0x98
> > > [ 6048.809918]  __hrtimer_run_queues+0x118/0x1a8
> > > [ 6048.814277]  hrtimer_interrupt+0xe4/0x238
> > > [ 6048.818296]  arch_timer_handler_phys+0x2c/0x38
> > > [ 6048.822743]  handle_percpu_devid_irq+0x80/0x140
> > > [ 6048.827277]  generic_handle_irq+0x24/0x38
> >
> > This is the timer interrupt which prompts the RCU splat. Do you have
> > information about where the CPU was when the interrupt occurred?
> >
> > In the meantime, it's still worth leaving the fuzzer running to see what
> > else it finds.
> 
> Overnight test done, only above rcu problem happen at both with and
> without ddr perf patches.

Great, thanks for giving it a go.

Will

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel