Re: [PATCH 1/2] sched/wait: Break up long wake list walk

[Linus Torvalds]

On Thu, Aug 17, 2017 at 9:17 AM, Liang, Kan <kan.liang@xxxxxxxxx> wrote:
>
> We tried both 12 and 16 bit table and that didn't make a difference.
> The long wake ups are mostly on the same page when we do instrumentation

Ok.

> Here is the wake_up_page_bit call stack when the workaround is running, which
> is collected by perf record -g -a -e probe:wake_up_page_bit -- sleep 10

It's actually not really wake_up_page_bit() that is all that
interesting, it would be more interesting to see which path it is that
*adds* the entries.

So it's mainly wait_on_page_bit_common(), but also add_page_wait_queue().

Can you get that call stack instead (or in addition to)?

                  Linus