Messages in this thread | | | Date | Tue, 28 Aug 2018 15:46:38 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH 08/11] asm-generic/tlb: Track freeing of page-table directories in struct mmu_gather |
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On Mon, Aug 27, 2018 at 02:44:57PM +1000, Nicholas Piggin wrote:
> powerpc may be able to use the unmap granule thing to improve > its page size dependent flushes, but it might prefer to go > a different way and track start-end for different page sizes.
I don't really see how tracking multiple ranges would help much with THP. The ranges would end up being almost the same if there is a good mix of page sizes.
But something like:
void tlb_flush_one(struct mmu_gather *tlb, unsigned long addr) { if (tlb->cleared_ptes && (addr << BITS_PER_LONG - PAGE_SHIFT)) tblie_pte(addr); if (tlb->cleared_pmds && (addr << BITS_PER_LONG - PMD_SHIFT)) tlbie_pmd(addr); if (tlb->cleared_puds && (addr << BITS_PER_LONG - PUD_SHIFT)) tlbie_pud(addr); }
void tlb_flush_range(struct mmu_gather *tlb) { unsigned long stride = 1UL << tlb_get_unmap_shift(tlb); unsigned long addr;
for (addr = tlb->start; addr < tlb->end; addr += stride) tlb_flush_one(tlb, addr);
ptesync(); }
Should workd I think. You'll only issue multiple TLBIEs on the boundaries, not every stride.
And for hugetlb the above should be optimal, since stride and tlb->cleared_* match up 1:1.
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