From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx155.postini.com [74.125.245.155]) by kanga.kvack.org (Postfix) with SMTP id 193C06B004D for ; Thu, 29 Dec 2011 22:39:23 -0500 (EST) Received: by qcsd17 with SMTP id d17so9987196qcs.14 for ; Thu, 29 Dec 2011 19:39:22 -0800 (PST) Message-ID: <4EFD3266.4080701@gmail.com> Date: Thu, 29 Dec 2011 22:39:18 -0500 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH 1/4] pagemap: avoid splitting thp when reading /proc/pid/pagemap References: <1324506228-18327-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1324506228-18327-2-git-send-email-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1324506228-18327-2-git-send-email-n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: linux-mm@kvack.org, Andrew Morton , David Rientjes , Andi Kleen , Wu Fengguang , Andrea Arcangeli , KOSAKI Motohiro , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org (12/21/11 5:23 PM), Naoya Horiguchi wrote: > Thp split is not necessary if we explicitly check whether pmds are > mapping thps or not. This patch introduces the check and the code > to generate pagemap entries for pmds mapping thps, which results in > less performance impact of pagemap on thp. > > Signed-off-by: Naoya Horiguchi > Reviewed-by: Andi Kleen > > Changes since v1: > - move pfn declaration to the beginning of pagemap_pte_range() > --- > fs/proc/task_mmu.c | 49 +++++++++++++++++++++++++++++++++++++++++++------ > 1 files changed, 43 insertions(+), 6 deletions(-) > > diff --git 3.2-rc5.orig/fs/proc/task_mmu.c 3.2-rc5/fs/proc/task_mmu.c > index e418c5a..0df61ab 100644 > --- 3.2-rc5.orig/fs/proc/task_mmu.c > +++ 3.2-rc5/fs/proc/task_mmu.c > @@ -600,6 +600,9 @@ struct pagemapread { > u64 *buffer; > }; > > +#define PAGEMAP_WALK_SIZE (PMD_SIZE) > +#define PAGEMAP_WALK_MASK (PMD_MASK) > + > #define PM_ENTRY_BYTES sizeof(u64) > #define PM_STATUS_BITS 3 > #define PM_STATUS_OFFSET (64 - PM_STATUS_BITS) > @@ -658,6 +661,22 @@ static u64 pte_to_pagemap_entry(pte_t pte) > return pme; > } > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +static u64 thp_pte_to_pagemap_entry(pte_t pte, int offset) > +{ > + u64 pme = 0; > + if (pte_present(pte)) When does pte_present() return 0? > + pme = PM_PFRAME(pte_pfn(pte) + offset) > + | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT; > + return pme; > +} > +#else > +static inline u64 thp_pte_to_pagemap_entry(pte_t pte, int offset) > +{ > + return 0; > +} > +#endif > + > static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > struct mm_walk *walk) > { > @@ -665,14 +684,34 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > struct pagemapread *pm = walk->private; > pte_t *pte; > int err = 0; > - > - split_huge_page_pmd(walk->mm, pmd); > + u64 pfn = PM_NOT_PRESENT; > > /* find the first VMA at or above 'addr' */ > vma = find_vma(walk->mm, addr); > - for (; addr != end; addr += PAGE_SIZE) { > - u64 pfn = PM_NOT_PRESENT; > > + spin_lock(&walk->mm->page_table_lock); > + if (pmd_trans_huge(*pmd)) { > + if (pmd_trans_splitting(*pmd)) { > + spin_unlock(&walk->mm->page_table_lock); > + wait_split_huge_page(vma->anon_vma, pmd); > + } else { > + for (; addr != end; addr += PAGE_SIZE) { > + int offset = (addr& ~PAGEMAP_WALK_MASK) > + >> PAGE_SHIFT; implicit narrowing conversion. offset should be unsigned long. > + pfn = thp_pte_to_pagemap_entry(*(pte_t *)pmd, > + offset); This (pte_t*) cast looks introduce new implicit assumption. Please don't put x86 assumption here directly. > + err = add_to_pagemap(addr, pfn, pm); > + if (err) > + break; > + } > + spin_unlock(&walk->mm->page_table_lock); > + return err; > + } > + } else { > + spin_unlock(&walk->mm->page_table_lock); > + } coding standard violation. plz run check_patch.pl. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org