Hello Petr, >> Hello, >> >> This is the v2 patch for hugepage filtering rebased on Petr's >> "Generic multi-page exclusion", thanks Petr. >> >> The current kernel's VMCOREINFO doesn't include necessary values >> for this patch, so we need "-x vmlinux" to enable hugepage filtering. >> I tested this patch on kernel 3.13. >> >> Regarding this, Petr made effort to add the values to VMCOREINFO, >> but it looks suspended: >> >> https://lkml.org/lkml/2014/4/11/349 > >Actually, I received an Acked-by from Vivek last Wednesday. Oh, wait a >moment, this email went to Andrew Morton, but not to any mailing >list. :-( > >> So, we should resume this discussion for this patch. Then, >> I should modify this patch to use PG_head_mask if it's accepted. > >I have already experimented with hugepage filtering, but haven't sent >my patches yet, precisely because they depend on a not-yet-confirmed >feature in the kernel. > >Anyway, let's take your patch as base. I'll add my comments where I >believe my approach was better/cleaner. Sorry for the late reply and thanks for your comments. I agree with you, so I'll post the fixed version soon. Thanks Atsushi Kumagai >> /* >> * If a multi-page exclusion is pending, do it first >> @@ -4727,6 +4779,27 @@ __exclude_unnecessary_pages(unsigned long mem_map, >> flags = ULONG(pcache + OFFSET(page.flags)); >> _count = UINT(pcache + OFFSET(page._count)); >> mapping = ULONG(pcache + OFFSET(page.mapping)); >> + >> + if (index_pg < PGMM_CACHED - 1) { >> + compound_order = ULONG(pcache + SIZE(page) + OFFSET(page.lru) >> + + OFFSET(list_head.prev)); >> + hugetlb_dtor = ULONG(pcache + SIZE(page) + OFFSET(page.lru) >> + + OFFSET(list_head.next)); >> + } else if (pfn + 1 < pfn_end) { > >AFAICS this clause is not needed. All compound pages are aligned to its >page order, e.g. the head page of an order-2 compound page is aligned >to a multiple of 4. Since mem_map cache is aligned to PGMM_CACHED, >which is defined as 512 (that is power of 2), a compound page cannot >possibly start on the last PFN of the cache. > >I even added a sanity check for the alignment: > > if (order && order < sizeof(unsigned long) * 8 && > (pfn & ((1UL << order) - 1)) == 0) > >Ok, the "order" above corresponds to your "compound_order"... > >> + unsigned char page_cache_next[SIZE(page)]; >> + if (!readmem(VADDR, mem_map, page_cache_next, SIZE(page))) { >> + ERRMSG("Can't read the buffer of struct page.\n"); >> + return FALSE; >> + } >> + compound_order = ULONG(page_cache_next + OFFSET(page.lru) >> + + OFFSET(list_head.prev)); >> + hugetlb_dtor = ULONG(page_cache_next + OFFSET(page.lru) >> + + OFFSET(list_head.next)); >> + } else { >> + compound_order = 0; >> + hugetlb_dtor = 0; >> + } >> + >> if (OFFSET(page._mapcount) != NOT_FOUND_STRUCTURE) >> _mapcount = UINT(pcache + OFFSET(page._mapcount)); >> if (OFFSET(page.private) != NOT_FOUND_STRUCTURE) >> @@ -4754,6 +4827,10 @@ __exclude_unnecessary_pages(unsigned long mem_map, >> && !isPrivate(flags) && !isAnon(mapping)) { >> if (clear_bit_on_2nd_bitmap_for_kernel(pfn, cycle)) >> pfn_cache++; >> + /* >> + * NOTE: If THP for cache is introduced, the check for >> + * compound pages is needed here. >> + */ > >I do this differently. I added: > > mdf_pfn_t *pfn_counter > >Then I set pfn_counter to the appropriate counter, but do not call >clear_bit_on_2nd_bitmap_for_kernel(). At the end of the long >if-else-if-else-if statement I add a final else-clause: > > /* > * Page not excluded > */ > else > continue; > >If execution gets here, the page is excluded, so I can do: > > if (nr_pages == 1) { > if (clear_bit_on_2nd_bitmap_for_kernel(pfn, cycle)) > (*pfn_counter)++; > } else { > exclude_range(pfn_counter, pfn, pfn + nr_pages, cycle); > } > >What do you think? > >Petr Tesarik
