From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id 813496B0388 for ; Mon, 13 Feb 2017 09:40:56 -0500 (EST) Received: by mail-it0-f71.google.com with SMTP id e137so151322699itc.0 for ; Mon, 13 Feb 2017 06:40:56 -0800 (PST) Received: from EUR01-DB5-obe.outbound.protection.outlook.com (mail-db5eur01on0130.outbound.protection.outlook.com. [104.47.2.130]) by mx.google.com with ESMTPS id k140si10866847ioe.44.2017.02.13.06.40.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 13 Feb 2017 06:40:55 -0800 (PST) Subject: Re: [PATCHv4 2/5] x86/mm: introduce mmap{,_legacy}_base References: <20170130120432.6716-1-dsafonov@virtuozzo.com> <20170130120432.6716-3-dsafonov@virtuozzo.com> From: Dmitry Safonov Message-ID: Date: Mon, 13 Feb 2017 17:37:09 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, 0x7f454c46@gmail.com, Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov , x86@kernel.org, linux-mm@kvack.org On 02/11/2017 05:13 PM, Thomas Gleixner wrote: >> -static unsigned long mmap_base(unsigned long rnd) >> +static unsigned long mmap_base(unsigned long rnd, unsigned long task_size) >> { >> unsigned long gap = rlimit(RLIMIT_STACK); > unsigned long gap_min, gap_max; > > /* Add comment what this means */ > gap_min = SIZE_128M + stack_maxrandom_size(task_size); > /* Explain that ' /6 * 5' magic */ > gap_max = (task_size / 6) * 5; So, I can't find about those limits on a gap size: They were introduced by commit 8913d55b6c58 ("i386 virtual memory layout rework"). All I could find is that 128Mb limit was more limit on virtual adress space than on a memory available those days. And 5/6 of task_size looks like heuristic value. So I'm not sure, what to write in comments: that rlimit on stack can't be bigger than 5/6 of task_size? That looks obvious from the code. -- Dmitry -- 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