From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f180.google.com (mail-pd0-f180.google.com [209.85.192.180]) by kanga.kvack.org (Postfix) with ESMTP id 6F9726B0038 for ; Wed, 18 Mar 2015 20:46:51 -0400 (EDT) Received: by pdbcz9 with SMTP id cz9so58736642pdb.3 for ; Wed, 18 Mar 2015 17:46:51 -0700 (PDT) Received: from mail-pa0-x235.google.com (mail-pa0-x235.google.com. [2607:f8b0:400e:c03::235]) by mx.google.com with ESMTPS id r4si39265793pdf.25.2015.03.18.17.46.50 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Mar 2015 17:46:50 -0700 (PDT) Received: by padcy3 with SMTP id cy3so58186415pad.3 for ; Wed, 18 Mar 2015 17:46:50 -0700 (PDT) Date: Thu, 19 Mar 2015 09:46:41 +0900 From: Minchan Kim Subject: Re: [PATCH 1/4] mm: free swp_entry in madvise_free Message-ID: <20150319004641.GC9153@blaptop> References: <1426036838-18154-1-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <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 Bump up. On Wed, Mar 11, 2015 at 10:20:35AM +0900, Minchan Kim wrote: > 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 > -- Kind regards, Minchan Kim -- 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