Messages in this thread | | | Date | Thu, 14 Jan 2021 12:52:48 +0100 | From | Oscar Salvador <> | Subject | Re: [External] Re: [PATCH v12 04/13] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page |
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On Thu, Jan 14, 2021 at 06:54:30PM +0800, Muchun Song wrote: > I think this approach may be only suitable for generic huge page only. > So we can implement it only for huge page. > > Hi Oscar, > > What's your opinion about this?
I tried something like:
static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) { pte_t *pte;
pte = pte_offset_kernel(pmd, addr);
if (!walk->reuse_page) { BUG_ON(pte_none(*pte));
walk->reuse_page = pte_page(*pte++); addr = walk->remap_start; }
for (; addr != end; addr += PAGE_SIZE, pte++) { BUG_ON(pte_none(*pte));
walk->remap_pte(pte, addr, walk); } }
void vmemmap_remap_free(unsigned long start, unsigned long end, unsigned long reuse) { LIST_HEAD(vmemmap_pages); struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_remap_pte, .reuse_addr = reuse, .remap_start = start, .vmemmap_pages = &vmemmap_pages, };
BUG_ON(start != reuse + PAGE_SIZE);
vmemmap_remap_range(reuse, end, &walk); free_vmemmap_page_list(&vmemmap_pages); }
but it might overcomplicate things and I am not sure it is any better. So I am fine with keeping it as is. Should another user come in the future, we can always revisit. Maybe just add a little comment in vmemmap_pte_range(), explaining while we are "+= PAGE_SIZE" for address and I would like to see a comment in vmemmap_remap_free why the BUG_ON and more important what it is checking.
-- Oscar Salvador SUSE L3
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