Messages in this thread | | | Date | Sat, 14 Oct 2023 11:11:54 +0800 | Subject | Re: [PATCH -next v2 09/19] mm: mprotect: use a folio in change_pte_range() | From | Kefeng Wang <> |
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On 2023/10/13 23:13, Matthew Wilcox wrote: > On Fri, Oct 13, 2023 at 04:55:53PM +0800, Kefeng Wang wrote: >> Use a folio in change_pte_range() to save three compound_head() calls. > > Yes, but here we have a change of behaviour, which should be argued > is desirable. Before if a partial THP was mapped, or a fs large > folio, we would do this to individual pages. Now we're doing it to the > entire folio. Is that desirable? I don't have the background to argue > either way.
The Huang's replay in v1[1] already mentioned this, we only use last_cpupid from head page, and large folio won't be handled from do_numa_page(), and if large folio numa balancing is supported, we could migrate the entire large folio mapped only one process, or maybe split the large folio mapped multi-processes, and when split it, we will copy the last_cpupid from head to the tail page. Anyway, I think this change or the wp_page_reuse() won't break current numa balancing.
Thanks.
[1]https://lore.kernel.org/linux-mm/874jixhfeu.fsf@yhuang6-desk2.ccr.corp.intel.com/ > >> @@ -157,7 +159,7 @@ static long change_pte_range(struct mmu_gather *tlb, >> continue; >> if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && >> !toptier) >> - xchg_page_access_time(page, >> + folio_xchg_access_time(folio, >> jiffies_to_msecs(jiffies)); >> } >
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