From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f177.google.com (mail-pf0-f177.google.com [209.85.192.177]) by kanga.kvack.org (Postfix) with ESMTP id DE0A86B0005 for ; Tue, 26 Jan 2016 17:49:27 -0500 (EST) Received: by mail-pf0-f177.google.com with SMTP id x125so643467pfb.0 for ; Tue, 26 Jan 2016 14:49:27 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id by6si3627703pad.69.2016.01.26.14.49.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jan 2016 14:49:27 -0800 (PST) Date: Tue, 26 Jan 2016 14:49:26 -0800 From: Andrew Morton Subject: Re: [PATCH v3] mm: warn about VmData over RLIMIT_DATA Message-Id: <20160126144926.21d854fe53b76bd03e34b0d1@linux-foundation.org> In-Reply-To: <145358234948.18573.2681359119037889087.stgit@zurg> References: <145358234948.18573.2681359119037889087.stgit@zurg> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov Cc: Cyrill Gorcunov , linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Vegard Nossum , Peter Zijlstra , Vladimir Davydov , Andy Lutomirski , Quentin Casasnovas , Kees Cook , Willy Tarreau , Pavel Emelyanov On Sat, 23 Jan 2016 23:52:29 +0300 Konstantin Khlebnikov wrote: > This patch fixes 84638335900f ("mm: rework virtual memory accounting") uh, I think I'll rewrite this to : This patch provides a way of working around a slight regression introduced : by 84638335900f ("mm: rework virtual memory accounting"). > Before that commit RLIMIT_DATA have control only over size of the brk region. > But that change have caused problems with all existing versions of valgrind, > because it set RLIMIT_DATA to zero. > > This patch fixes rlimit check (limit actually in bytes, not pages) > and by default turns it into warning which prints at first VmData misuse: > "mmap: top (795): VmData 516096 exceed data ulimit 512000. Will be forbidden soon." > > Behavior is controlled by boot param ignore_rlimit_data=y/n and by sysfs > /sys/module/kernel/parameters/ignore_rlimit_data. For now it set to "y". > > > ... > > +static inline bool is_data_mapping(vm_flags_t flags) > +{ > + return (flags & ((VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)) | > + VM_WRITE | VM_SHARED)) == VM_WRITE; > +} This (copied from existing code) hurts my brain. We're saying "if it isn't stack and it's unshared and writable, it's data", yes? hm. I guess that's because with a shared mapping we don't know who to blame for the memory consumption so we blame nobody. But what about non-shared read-only mappings? Can we please have a comment here fully explaining the thinking? -- 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