From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 5883790002E for ; Tue, 10 Mar 2015 21:20:50 -0400 (EDT) Received: by padfa1 with SMTP id fa1so6792233pad.9 for ; Tue, 10 Mar 2015 18:20:50 -0700 (PDT) Received: from lgemrelse7q.lge.com (LGEMRELSE7Q.lge.com. [156.147.1.151]) by mx.google.com with ESMTP id fe5si4178215pdb.39.2015.03.10.18.20.45 for ; Tue, 10 Mar 2015 18:20:47 -0700 (PDT) From: Minchan Kim Subject: [PATCH 1/4] mm: free swp_entry in madvise_free Date: Wed, 11 Mar 2015 10:20:35 +0900 Message-Id: <1426036838-18154-1-git-send-email-minchan@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Johannes Weiner , Mel Gorman , Rik van Riel , Shaohua Li , Yalin.Wang@sonymobile.com, Minchan Kim When I test below piece of code with 12 processes(ie, 512M * 12 = 6G consume) on my (3G ram + 12 cpu + 8G swap, the madvise_free is siginficat slower (ie, 2x times) than madvise_dontneed. loop = 5; mmap(512M); while (loop--) { memset(512M); madvise(MADV_FREE or MADV_DONTNEED); } The reason is lots of swapin. 1) dontneed: 1,612 swapin 2) madvfree: 879,585 swapin If we find hinted pages were already swapped out when syscall is called, it's pointless to keep the swapped-out pages in pte. Instead, let's free the cold page because swapin is more expensive than (alloc page + zeroing). With this patch, it reduced swapin from 879,585 to 1,878 so elapsed time 1) dontneed: 6.10user 233.50system 0:50.44elapsed 2) madvfree: 6.03user 401.17system 1:30.67elapsed 2) madvfree + below patch: 6.70user 339.14system 1:04.45elapsed Signed-off-by: Minchan Kim --- mm/madvise.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 6d0fcb8..ebe692e 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -274,7 +274,9 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, spinlock_t *ptl; pte_t *pte, ptent; struct page *page; + swp_entry_t entry; unsigned long next; + int nr_swap = 0; next = pmd_addr_end(addr, end); if (pmd_trans_huge(*pmd)) { @@ -293,8 +295,22 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, for (; addr != end; pte++, addr += PAGE_SIZE) { ptent = *pte; - if (!pte_present(ptent)) + if (pte_none(ptent)) continue; + /* + * If the pte has swp_entry, just clear page table to + * prevent swap-in which is more expensive rather than + * (page allocation + zeroing). + */ + if (!pte_present(ptent)) { + entry = pte_to_swp_entry(ptent); + if (non_swap_entry(entry)) + continue; + nr_swap--; + free_swap_and_cache(entry); + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); + continue; + } page = vm_normal_page(vma, addr, ptent); if (!page) @@ -326,6 +342,14 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, set_pte_at(mm, addr, pte, ptent); tlb_remove_tlb_entry(tlb, pte, addr); } + + if (nr_swap) { + if (current->mm == mm) + sync_mm_rss(mm); + + add_mm_counter(mm, MM_SWAPENTS, nr_swap); + } + arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte - 1, ptl); next: -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org