From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx107.postini.com [74.125.245.107]) by kanga.kvack.org (Postfix) with SMTP id BF7446B0095 for ; Mon, 12 Dec 2011 08:26:19 -0500 (EST) Date: Mon, 12 Dec 2011 14:26:16 +0100 From: Michal Hocko Subject: Re: [PATCH v3] mm: simplify find_vma_prev Message-ID: <20111212132616.GB15249@tiehlicka.suse.cz> References: <1323466526.27746.29.camel@joe2Laptop> <1323470921-12931-1-git-send-email-kosaki.motohiro@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1323470921-12931-1-git-send-email-kosaki.motohiro@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: kosaki.motohiro@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, KOSAKI Motohiro , Andrew Morton , Hugh Dickins , Peter Zijlstra , Shaohua Li On Fri 09-12-11 17:48:40, kosaki.motohiro@gmail.com wrote: > From: KOSAKI Motohiro > > commit 297c5eee37 (mm: make the vma list be doubly linked) added > vm_prev member into vm_area_struct. Therefore we can simplify > find_vma_prev() by using it. Also, this change help to improve > page fault performance because it has strong locality of reference. > > Signed-off-by: KOSAKI Motohiro > --- > mm/mmap.c | 36 ++++++++---------------------------- > 1 files changed, 8 insertions(+), 28 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index eae90af..b9c0241 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1603,39 +1603,19 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) > > EXPORT_SYMBOL(find_vma); > > -/* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */ > +/* > + * Same as find_vma, but also return a pointer to the previous VMA in *pprev. > + * Note: pprev is set to NULL when return value is NULL. > + */ > struct vm_area_struct * > find_vma_prev(struct mm_struct *mm, unsigned long addr, > struct vm_area_struct **pprev) > { > - struct vm_area_struct *vma = NULL, *prev = NULL; > - struct rb_node *rb_node; > - if (!mm) > - goto out; > - > - /* Guard against addr being lower than the first VMA */ > - vma = mm->mmap; Why have you removed this guard? Previously we had pprev==NULL and returned mm->mmap. This seems like a semantic change without any explanation. Could you clarify? > - > - /* Go through the RB tree quickly. */ > - rb_node = mm->mm_rb.rb_node; > - > - while (rb_node) { > - struct vm_area_struct *vma_tmp; > - vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb); > - > - if (addr < vma_tmp->vm_end) { > - rb_node = rb_node->rb_left; > - } else { > - prev = vma_tmp; > - if (!prev->vm_next || (addr < prev->vm_next->vm_end)) > - break; > - rb_node = rb_node->rb_right; > - } > - } > + struct vm_area_struct *vma; > > -out: > - *pprev = prev; > - return prev ? prev->vm_next : vma; > + vma = find_vma(mm, addr); > + *pprev = vma ? vma->vm_prev : NULL; > + return vma; > } > > /* > -- > 1.7.1 > > -- > 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 -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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