On 8/2/2023 8:40 PM, Ryan Roberts wrote: > On 02/08/2023 13:35, Yin, Fengwei wrote: >> >> >> On 8/2/2023 6:27 PM, Ryan Roberts wrote: >>> On 28/07/2023 17:13, Yin Fengwei wrote: >>>> In madvise_cold_or_pageout_pte_range() and madvise_free_pte_range(), >>>> folio_mapcount() is used to check whether the folio is shared. But it's >>>> not correct as folio_mapcount() returns total mapcount of large folio. >>>> >>>> Use folio_estimated_sharers() here as the estimated number is enough. >>>> >>>> Yin Fengwei (2): >>>> madvise: don't use mapcount() against large folio for sharing check >>>> madvise: don't use mapcount() against large folio for sharing check >>>> >>>> mm/huge_memory.c | 2 +- >>>> mm/madvise.c | 6 +++--- >>>> 2 files changed, 4 insertions(+), 4 deletions(-) >>>> >>> >>> As a set of fixes, I agree this is definitely an improvement, so: >>> >>> Reviewed-By: Ryan Roberts >> Thanks. >> >>> >>> >>> But I have a couple of comments around further improvements; >>> >>> Once we have the scheme that David is working on to be able to provide precise >>> exclusive vs shared info, we will probably want to move to that. Although that >>> scheme will need access to the mm_struct of a process known to be mapping the >>> folio. We have that info, but its not passed to folio_estimated_sharers() so we >>> can't just reimplement folio_estimated_sharers() - we will need to rework these >>> call sites again. >> Yes. This could be extra work. Maybe should delay till David's work is done. > > What you have is definitely an improvement over what was there before. And is > probably the best we can do without David's scheme. So I wouldn't delay this. > Just pointing out that we will be able to make it even better later on (if > David's stuff goes in). Yes. I agree that we should wait for David's work ready and do fix based on that. Regards Yin, Fengwei > >> >>> >>> Given the aspiration for most of the memory to be large folios going forwards, >>> wouldn't it be better to avoid splitting the large folio where the large folio >>> is mapped entirely within the range of the madvise operation? Sorry if this has >>> already been discussed and decided against - I didn't follow the RFC too >>> closely. Or perhaps you plan to do this as a follow up? >> Yes. We are on same page. RFC patchset did that. But there are some other opens >> on the RFC. So I tried to submit this part of change which is bug fix. The other >> thing left in RFC is optimization (avoid split large folio if we can). >> >> >> Regards >> Yin, Fengwei >> >>> >>> Thanks, >>> Ryan >>> > >
