| Message ID | 20240605095304.66389-3-alexs@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC,1/3] mm/ksm: add anonymous check in find_mergeable_vma | expand |
Let me withdraw this patch, the flush_anon_page come with the first patchset of ksm, and no explanation for them. Though, no any guarantee for concurrent page write for the flush, but anyway I give up on the flush optimize. Sorry for disturber. Alex On 6/5/24 5:53 PM, alexs@kernel.org wrote: > From: "Alex Shi (tencent)" <alexs@kernel.org> > > commit 6020dff09252 ("[ARM] Resolve fuse and direct-IO failures due to missing cache flushes") > explain that the aim of flush_anon_page() is to keep the cache and memory > content synced. Also as David Hildenbrand pointed, flush page without > the page contents reading here is meaningless, so let's move the flush action > just before page contents reading, like calc_checksum(), not > just find a page, flush it, w/o clear purpose. This should save some flush > actions why keep page content safely synced. > > BTW, write_protect_page() do another type flush actions before pages_identical(). > > Signed-off-by: Alex Shi (tencent) <alexs@kernel.org> > --- > mm/ksm.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index ef335ee508d3..77e8c1ded9bb 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -784,10 +784,7 @@ static struct page *get_mergeable_page(struct ksm_rmap_item *rmap_item) > goto out; > if (is_zone_device_page(page)) > goto out_putpage; > - if (PageAnon(page)) { > - flush_anon_page(vma, page, addr); > - flush_dcache_page(page); > - } else { > + if (!PageAnon(page)) { > out_putpage: > put_page(page); > out: > @@ -2378,7 +2375,12 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite > mmap_read_unlock(mm); > return; > } > + > + /* flush page contents before calculate checksum */ > + flush_anon_page(vma, page, rmap_item->address); > + flush_dcache_page(page); > checksum = calc_checksum(page); > + > if (rmap_item->oldchecksum != checksum) { > rmap_item->oldchecksum = checksum; > mmap_read_unlock(mm); > @@ -2662,8 +2664,6 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > if (is_zone_device_page(*page)) > goto next_page; > if (PageAnon(*page)) { > - flush_anon_page(vma, *page, ksm_scan.address); > - flush_dcache_page(*page); > rmap_item = get_next_rmap_item(mm_slot, > ksm_scan.rmap_list, ksm_scan.address); > if (rmap_item) {
diff --git a/mm/ksm.c b/mm/ksm.c index ef335ee508d3..77e8c1ded9bb 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -784,10 +784,7 @@ static struct page *get_mergeable_page(struct ksm_rmap_item *rmap_item) goto out; if (is_zone_device_page(page)) goto out_putpage; - if (PageAnon(page)) { - flush_anon_page(vma, page, addr); - flush_dcache_page(page); - } else { + if (!PageAnon(page)) { out_putpage: put_page(page); out: @@ -2378,7 +2375,12 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite mmap_read_unlock(mm); return; } + + /* flush page contents before calculate checksum */ + flush_anon_page(vma, page, rmap_item->address); + flush_dcache_page(page); checksum = calc_checksum(page); + if (rmap_item->oldchecksum != checksum) { rmap_item->oldchecksum = checksum; mmap_read_unlock(mm); @@ -2662,8 +2664,6 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) if (is_zone_device_page(*page)) goto next_page; if (PageAnon(*page)) { - flush_anon_page(vma, *page, ksm_scan.address); - flush_dcache_page(*page); rmap_item = get_next_rmap_item(mm_slot, ksm_scan.rmap_list, ksm_scan.address); if (rmap_item) {