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

Paul Mackerras
2008-11-17T22:19:55Z

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

Paul.