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. > > 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 >
