From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f173.google.com (mail-io0-f173.google.com [209.85.223.173]) by kanga.kvack.org (Postfix) with ESMTP id 523406B0038 for ; Mon, 14 Dec 2015 12:54:50 -0500 (EST) Received: by iofo67 with SMTP id o67so51988883iof.3 for ; Mon, 14 Dec 2015 09:54:50 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id m81si3444779iom.134.2015.12.14.09.54.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Dec 2015 09:54:49 -0800 (PST) Date: Mon, 14 Dec 2015 18:55:09 +0100 From: Oleg Nesterov Subject: Re: [RFC] mm: change find_vma() function Message-ID: <20151214175509.GA25681@redhat.com> References: <1450090945-4020-1-git-send-email-yalin.wang2010@gmail.com> <20151214121107.GB4201@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151214121107.GB4201@node.shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: yalin wang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, gang.chen.5i5j@gmail.com, mhocko@suse.com, kwapulinski.piotr@gmail.com, aarcange@redhat.com, dcashman@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 12/14, Kirill A. Shutemov wrote: > > On Mon, Dec 14, 2015 at 07:02:25PM +0800, yalin wang wrote: > > change find_vma() to break ealier when found the adderss > > is not in any vma, don't need loop to search all vma. > > > > Signed-off-by: yalin wang > > --- > > mm/mmap.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index b513f20..8294c9b 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -2064,6 +2064,9 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) > > vma = tmp; > > if (tmp->vm_start <= addr) > > break; > > + if (!tmp->vm_prev || tmp->vm_prev->vm_end <= addr) > > + break; > > + > > This 'break' would return 'tmp' as found vma. But this would be right? Not that I think this optimization makes sense, I simply do not know, but to me this change looks technically correct at first glance... But the changelog is wrong or I missed something. This change can stop the main loop earlier; if "tmp" is the first vma, or if the previous one is below the address. Or perhaps I just misread that "not in any vma" note in the changelog. No? Oleg. -- 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