Re: Large stack usage in fs code (especially for PPC64)

Steven Rostedt
2008-11-17T23:31:14Z

On Tue, 18 Nov 2008, Paul Mackerras wrote:

> Steven Rostedt writes:
>
> > Here's my stack after boot up with CONFIG_IRQSTACKS set. Seems that
> > softirqs still use the same stack as the process.
>
> They shouldn't. I don't see do_softirq in the trace, though. Which
> functions did you think would be run in a softirq? It looks to me
> like the deepest 10 or so functions are called at hard irq level,
> within hrtimer_interrupt called from timer_interrupt.
>
> > root@electra ~> cat /debug/tracing/stack_trace
> > Depth Size Location (59 entries)
> > ----- ---- --------
> > 0) 12384 192 ftrace_call+0x4/0x14
> > 1) 12192 128 .sched_clock+0x20/0x60
> > 2) 12064 128 .sched_clock_cpu+0x34/0x50
> > 3) 11936 144 .cpu_clock+0x3c/0xa0
> > 4) 11792 144 .get_timestamp+0x2c/0x50
> > 5) 11648 144 .__touch_softlockup_watchdog+0x3c/0x60
> > 6) 11504 192 .softlockup_tick+0xe4/0x220
> > 7) 11312 128 .run_local_timers+0x34/0x50
> > 8) 11184 160 .update_process_times+0x44/0xb0
> > 9) 11024 176 .tick_sched_timer+0x8c/0x120
> > 10) 10848 160 .__run_hrtimer+0xd8/0x130
> > 11) 10688 240 .hrtimer_interrupt+0x16c/0x220
> > 12) 10448 160 .timer_interrupt+0xcc/0x110
> > 13) 10288 96 decrementer_common+0xe0/0x100

Ah, you are right. I thought I saw softirq code in there, but must have
been seeing things. I need to get my eyesight checked. The other day I
totally botch a hand in cards because I thought I had 3 Aces of diamonds
when I really only had 2 Aces of diamonds and a Ace of hearts.

-- Steve