Re: [PATCH 00/25] mm: Page fault accounting cleanups

Linus Torvalds [off-list ref] writes:

On Mon, Jun 15, 2020 at 3:16 PM Peter Xu [off-list ref] wrote:

quoted

This series tries to address all of them by introducing mm_fault_accounting()
first, so that we move all the page fault accounting into the common code base,
then call it properly from arch pf handlers just like handle_mm_fault().

Hmm.

So having looked at this a bit more, I'd actually like to go even
further, and just get rid of the per-architecture code _entirely_.

<snip>

One detail worth noting: I do wonder if we should put the

    perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

just in the arch code at the top of the fault handling, and consider
it entirely unrelated to the major/minor fault handling. The
major/minor faults fundamnetally are about successes. But the plain
PERF_COUNT_SW_PAGE_FAULTS could be about things that fail, including
things that never even get to this point at all.

Yeah I think we should keep it in the arch code at roughly the top.

If it's moved to the end you could have a process spinning taking bad
page faults (and fixing them up), and see no sign of it from the perf
page fault counters.

cheers

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