Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755292AbZG0WTu (ORCPT ); Mon, 27 Jul 2009 18:19:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752668AbZG0WTt (ORCPT ); Mon, 27 Jul 2009 18:19:49 -0400 Received: from fg-out-1718.google.com ([72.14.220.154]:1048 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752649AbZG0WTs convert rfc822-to-8bit (ORCPT ); Mon, 27 Jul 2009 18:19:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=hkUdbgQHhZfQj58ZuK07BgAmkTmhnNfVkJD3FKTPhY3x8flvHVwAMZIAGPQgWVJ2yr u2mB8P+HyDvA8DOcDi0zqB0lW+c6RxPGKn5eAyzsKrmsdS4QyQDmhrHdqVHUl698DO7O l3U/51s1NEIqk76W/N3uelNz9kvRoT288oT2M= MIME-Version: 1.0 In-Reply-To: References: <4A693122.6060503@gmail.com> <20090724083926.GA6372@cr0.nay.redhat.com> <4A6E0BD6.50102@gmail.com> Date: Mon, 27 Jul 2009 15:14:30 -0700 Message-ID: <7928e7bd0907271514y699d1de4j54f9c562b94ef0cc@mail.gmail.com> Subject: Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or mapped vma clearing From: Moussa Ba To: David Rientjes Cc: linux-kernel@vger.kernel.org, xiyou.wangcong@gmail.com, Andrew Morton , Alexey Dobriyan , Matt Mackall , Mel Gorman , Ying Han , Nick Piggin , jaredeh@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7369 Lines: 205 On Mon, Jul 27, 2009 at 1:57 PM, David Rientjes wrote: > On Mon, 27 Jul 2009, Moussa A. Ba wrote: > >> This patch makes the clear_refs proc interface a bit more versatile. >> It adds support ?for clearing anonymous pages, file mapped pages or both. >> > > It already has support for clearing both, so you're only adding anonymous > and file-backed filters. > >> The clear_refs entry is used to reset the Referenced bits on virtual and >> physical pages associated with a process. >> echo 1 > /proc/PID/clear_refs clears all pages associated with the process >> echo 2 > /proc/PID/clear_refs clears anonymous pages only >> echo 3 > /proc/PID/clear_refs clears file mapped pages only >> Any other value written to the proc entry will clear all pages. >> > > clear_refs currently accepts any non-zero value, so it's possible that > this will break user scripts that, for whatever reason, write '2' or '3'. > I think that's acceptable, but it would be helpful to make all other > values a no-op similar to drop_caches at this point to avoid the potential > for breakage if this is ever extended any further. > >> Selective clearing the pages has a measurable impact on performance as it >> limits the number of page walks. ?We have been using this interface and ?this >> adds flexibility to the user user space application implementing the reference >> clearing. >> >> Signed-off-by: Jared Hulbert (jaredeh@gmail.com) >> Signed-off-by: Moussa A. Ba (moussa.a.ba@gmail.com) > > Email addresses in < > braces, please. > > The first sign-off line normally indicates who wrote the patch, but your > submission lacks a From: line, so git would indicate you wrote it. ?If > that's incorrect, please add a From: line as described in > Documentation/SubmittingPatches. ?If it's correct, please reorder your > sign-off lines. > I will reorder the sign-off lines >> ------- >> Documentation/filesystems/proc.txt | ? ?7 +++++++ >> fs/proc/task_mmu.c ? ? ? ? ? ? ? ? | ? 29 +++++++++++++++++++++++++---- >> 2 files changed, 32 insertions(+), 4 deletions(-) >> >> --- a/fs/proc/task_mmu.c ? ? ?2009-07-21 14:30:01.000000000 -0700 >> +++ b/fs/proc/task_mmu.c ? ? ?2009-07-27 11:46:05.000000000 -0700 >> @@ -462,6 +462,27 @@ >> ? ? ? return 0; >> ?} >> >> +static void walk_vma_area(struct mm_walk *this_walk, >> + ? ? ? ? ? ? ? ? ? ? ? struct vm_area_struct *vma, int type) >> +{ > > This is a very generic name for something that is only applicable to > clear_refs, so please name it accordingly. ?This will also avoid having to > pass the struct mm_walk * in since its only user is clear_refs_walk. > Done. >> + >> + ? ? /* Writing 2 to /proc/pid/clear_refs will clear all Anonymous >> + ? ? ?* pages. >> + ? ? ?* >> + ? ? ?* Writing 3 to /proc/pid/clear_refs will clear all file mapped >> + ? ? ?* pages. >> + ? ? ?* >> + ? ? ?* Writing any other value including 1 will clear all pages >> + ? ? ?*/ > > Documentation/CodingStyle would suggest this format: > > ? ? ? ?/* > ? ? ? ? * Multi-line kernel comments always start .. > ? ? ? ? * with an empty first line. > ? ? ? ? */ > Done. >> + ? ? if (is_vm_hugetlb_page(vma)) >> + ? ? ? ? ? ? return; >> + ? ? if (type == 2 && vma->vm_file) >> + ? ? ? ? ? ? return; >> + ? ? if (type == 3 && !vma->vm_file) >> + ? ? ? ? ? ? return; >> + ? ? walk_page_range(vma->vm_start, vma->vm_end, this_walk); >> +} > > K&R would suggest #define's (or enums) for those hard-coded values. ?I > think that's already been suggested for this patch, actually. > Would this be acceptable? enum clear_refs_walk_type { CLEAR_REFS_ALL = 1, CLEAR_REFS_ANON = 2, CLEAR_REFS_MAPPED = 3 }; static void clear_refs_walk_vma_area(struct mm_walk *this_walk, struct vm_area_struct *vma, enum clear_refs_walk_type type) { /* * Writing 1 to /proc/pid/clear_refs clears all pages. * Writing 2 to /proc/pid/clear_refs clears Anonymous pages. * Writing 3 to /proc/pid/clear_refs clears file mapped pages. */ if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED) return; if (is_vm_hugetlb_page(vma)) return; if (type == CLEAR_REFS_ANON && vma->vm_file) return; if (type == CLEAR_REFS_MAPPED && !vma->vm_file) return; walk_page_range(vma->vm_start, vma->vm_end, this_walk); } >> + >> ?static ssize_t clear_refs_write(struct file *file, const char __user * buf, >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? size_t count, loff_t * ppos) >> ?{ >> @@ -469,13 +490,15 @@ >> ? ? ? char buffer[PROC_NUMBUF], *end; >> ? ? ? struct mm_struct *mm; >> ? ? ? struct vm_area_struct *vma; >> + ? ? int type; >> >> ? ? ? memset(buffer, 0, sizeof(buffer)); >> ? ? ? if (count > sizeof(buffer) - 1) >> ? ? ? ? ? ? ? count = sizeof(buffer) - 1; >> ? ? ? if (copy_from_user(buffer, buf, count)) >> ? ? ? ? ? ? ? return -EFAULT; >> - ? ? if (!simple_strtol(buffer, &end, 0)) >> + ? ? type = strict_strtol(buffer, &end, 0); >> + ? ? if (!type) >> ? ? ? ? ? ? ? return -EINVAL; >> ? ? ? if (*end == '\n') >> ? ? ? ? ? ? ? end++; >> @@ -491,9 +514,7 @@ >> ? ? ? ? ? ? ? down_read(&mm->mmap_sem); >> ? ? ? ? ? ? ? for (vma = mm->mmap; vma; vma = vma->vm_next) { >> ? ? ? ? ? ? ? ? ? ? ? clear_refs_walk.private = vma; >> - ? ? ? ? ? ? ? ? ? ? if (!is_vm_hugetlb_page(vma)) >> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? walk_page_range(vma->vm_start, vma->vm_end, >> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? &clear_refs_walk); >> + ? ? ? ? ? ? ? ? ? ? walk_vma_area(&clear_refs_walk, vma, type); >> ? ? ? ? ? ? ? } >> ? ? ? ? ? ? ? flush_tlb_mm(mm); >> ? ? ? ? ? ? ? up_read(&mm->mmap_sem); >> --- a/Documentation/filesystems/proc.txt ? ? ?2009-07-20 17:29:11.000000000 >> -0700 >> +++ b/Documentation/filesystems/proc.txt ? ? ?2009-07-27 12:08:34.000000000 >> -0700 >> @@ -375,6 +375,13 @@ >> ?This file is only present if the CONFIG_MMU kernel configuration option is >> ?enabled. >> >> +The clear_refs entry is used to reset the Referenced bits on virtual and physical >> +pages associated with a process. >> +echo 1 > /proc/PID/clear_refs clears all pages associated with the process >> +echo 2 > /proc/PID/clear_refs clears anonymous pages only >> +echo 3 > /proc/PID/clear_refs clears file mapped pages only >> +Any other value written to the proc entry will clear all pages. >> + > > Please follow the format in this document for how other /proc/PID/* > entries are described. > > That format could really be improved here, perhaps you could clean > proc.txt up a little bit while you're here? > > I am not sure what you mean by "clean" proc.txt, I did not detect much formatting in the PID proc enries description, beyond what I rewrote below: The /proc/PID/clear_refs is used to reset the Referenced bits on virtual and physical pages associated with a process. To clear all pages associated with the process > echo 1 > /proc/PID/clear_refs To clear all anonymous pages associated with the process > echo 2 > /proc/PID/clear_refs To clear all file mapped pages associated with the process > echo 3 > /proc/PID/clear_refs Any other value written to /proc/PID/clear_refs will have no effect. > Also, as the author of clear_refs, please cc me on future revisions of > this patch. > I shall. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/