From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx110.postini.com [74.125.245.110]) by kanga.kvack.org (Postfix) with SMTP id E15116B0033 for ; Thu, 13 Jun 2013 17:06:34 -0400 (EDT) Date: Thu, 13 Jun 2013 14:06:32 -0700 From: Andrew Morton Subject: Re: [PATCH] mm: Revert pinned_vm braindamage Message-Id: <20130613140632.15982af2ebc443b24bfff86a@linux-foundation.org> In-Reply-To: <20130606124351.GZ27176@twins.programming.kicks-ass.net> References: <20130606124351.GZ27176@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: torvalds@linux-foundation.org, roland@kernel.org, mingo@kernel.org, tglx@linutronix.de, kosaki.motohiro@gmail.com, penberg@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org, Mike Marciniszyn Let's try to get this wrapped up? On Thu, 6 Jun 2013 14:43:51 +0200 Peter Zijlstra wrote: > > Patch bc3e53f682 ("mm: distinguish between mlocked and pinned pages") > broke RLIMIT_MEMLOCK. I rather like what bc3e53f682 did, actually. RLIMIT_MEMLOCK limits the amount of memory you can mlock(). Nice and simple. This pinning thing which infiniband/perf are doing is conceptually different and if we care at all, perhaps we should be looking at adding RLIMIT_PINNED. > Before that patch: mm_struct::locked_vm < RLIMIT_MEMLOCK; after that > patch we have: mm_struct::locked_vm < RLIMIT_MEMLOCK && > mm_struct::pinned_vm < RLIMIT_MEMLOCK. But this is a policy decision which was implemented in perf_mmap() and perf can alter that decision. How bad would it be if perf just ignored RLIMIT_MEMLOCK? drivers/infiniband/hw/qib/qib_user_pages.c has issues, btw. It compares the amount-to-be-pinned with rlimit(RLIMIT_MEMLOCK), but forgets to also look at current->mm->pinned_vm. Duh. It also does the pinned accounting in __qib_get_user_pages() but in __qib_release_user_pages(), the caller is supposed to do it, which is rather awkward. Longer-term I don't think that inifinband or perf should be dinking around with rlimit(RLIMIT_MEMLOCK) or ->pinned_vm. Those policy decisions should be hoisted into a core mm helper where we can do it uniformly (and more correctly than infiniband's attempt!). -- 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