From 617c28ecab22d98a3809370eb6cb50fa24b7bfe1 Mon Sep 17 00:00:00 2001 From: Yin Fengwei Date: Wed, 2 Aug 2023 16:14:05 +0100 Subject: [PATCH] filemap: batch PTE mappings Call set_pte_range() once per contiguous range of the folio instead of once per page. This batches the updates to mm counters and the rmap. With a will-it-scale.page_fault3 like app (change file write fault testing to read fault testing. Trying to upstream it to will-it-scale at [1]) got 15% performance gain on a 48C/96T Cascade Lake test box with 96 processes running against xfs. Perf data collected before/after the change: 18.73%--page_add_file_rmap | --11.60%--__mod_lruvec_page_state | |--7.40%--__mod_memcg_lruvec_state | | | --5.58%--cgroup_rstat_updated | --2.53%--__mod_lruvec_state | --1.48%--__mod_node_page_state 9.93%--page_add_file_rmap_range | --2.67%--__mod_lruvec_page_state | |--1.95%--__mod_memcg_lruvec_state | | | --1.57%--cgroup_rstat_updated | --0.61%--__mod_lruvec_state | --0.54%--__mod_node_page_state The running time of __mode_lruvec_page_state() is reduced about 9%. [1]: https://github.com/antonblanchard/will-it-scale/pull/37 Link: https://lkml.kernel.org/r/20230802151406.3735276-38-willy@infradead.org Signed-off-by: Yin Fengwei Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/filemap.c | 43 +++++++++++++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 14 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index c06e9d331416..014b73eb96a1 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3480,11 +3480,12 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, struct file *file = vma->vm_file; struct page *page = folio_page(folio, start); unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss); - unsigned int ref_count = 0, count = 0; + unsigned int count = 0; + pte_t *old_ptep = vmf->pte; do { - if (PageHWPoison(page)) - continue; + if (PageHWPoison(page + count)) + goto skip; if (mmap_miss > 0) mmap_miss--; @@ -3494,20 +3495,34 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, * handled in the specific fault path, and it'll prohibit the * fault-around logic. */ - if (!pte_none(*vmf->pte)) - continue; + if (!pte_none(vmf->pte[count])) + goto skip; - if (vmf->address == addr) + count++; + continue; +skip: + if (count) { + set_pte_range(vmf, folio, page, count, addr); + folio_ref_add(folio, count); + if (in_range(vmf->address, addr, count)) + ret = VM_FAULT_NOPAGE; + } + + count++; + page += count; + vmf->pte += count; + addr += count * PAGE_SIZE; + count = 0; + } while (--nr_pages > 0); + + if (count) { + set_pte_range(vmf, folio, page, count, addr); + folio_ref_add(folio, count); + if (in_range(vmf->address, addr, count)) ret = VM_FAULT_NOPAGE; + } - ref_count++; - set_pte_range(vmf, folio, page, 1, addr); - } while (vmf->pte++, page++, addr += PAGE_SIZE, ++count < nr_pages); - - /* Restore the vmf->pte */ - vmf->pte -= nr_pages; - - folio_ref_add(folio, ref_count); + vmf->pte = old_ptep; WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); return ret;