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SubjectVery low responsiveness for pstore ftrace
Date
Hi folks,

I'm newbie to pstore. I just did a quick try for pstore ftrace. But, I
experience very serious responsiveness problem. When running "echo 1 >
/sys/kernel/debug/pstore/record_ftrace", it took a couple of minutes to
return (here return means to get prompt back) on my arm64 machine (8 A57
cores). time command shows:

# time echo 1 > /sys/kernel/debug/pstore/record_ftrace
hrtimer: interrupt took 17532560 ns

real 7m35.717s
user 0m0.004s
sys 2m25.244s


I had a quick look at the code, it looks there is a long critical
section with irq disabled.

If with CONFIG_PSTORE_CONSOLE enabled, the machine even can't response
interrupts. The pstore console code also need acquire the same lock with
irq disabled.

The low responsiveness sounds not reasonable to me.

Any idea?

Thanks,
Yang





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