From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx190.postini.com [74.125.245.190]) by kanga.kvack.org (Postfix) with SMTP id 1F02A6B0034 for ; Thu, 20 Jun 2013 10:48:58 -0400 (EDT) Date: Thu, 20 Jun 2013 14:48:56 +0000 From: Christoph Lameter Subject: Re: [PATCH] mm: Revert pinned_vm braindamage In-Reply-To: <20130620114943.GB12125@gmail.com> Message-ID: <0000013f620f4699-f484f28e-3d12-4560-adfe-3b00af995fd9-000000@email.amazonses.com> References: <20130606124351.GZ27176@twins.programming.kicks-ass.net> <0000013f1ad00ec0-9574a936-3a75-4ccc-a84c-4a12a7ea106e-000000@email.amazonses.com> <20130607110344.GA27176@twins.programming.kicks-ass.net> <0000013f1f1f79d1-2cf8cb8c-7e63-4e83-9f2b-7acc0e0638a1-000000@email.amazonses.com> <20130617110832.GP3204@twins.programming.kicks-ass.net> <0000013f536c60ee-9a1ca9da-b798-416a-a32e-c896813d3bac-000000@email.amazonses.com> <20130620114943.GB12125@gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: Peter Zijlstra , akpm@linux-foundation.org, torvalds@linux-foundation.org, roland@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 On Thu, 20 Jun 2013, Ingo Molnar wrote: > Peter clearly pointed it out that in the perf case it's user-space that > initiates the pinned memory mapping which is resource-controlled via > RLIMIT_MEMLOCK - and this was implemented that way before your commit > broke the code. There is no way that user space can initiate a page pin right now. Perf is pinning the page from the kernel. Similarly the IB subsystem pins memory meeded for device I/O. > You seem to be hell bent on defining 'memory pinning' only as "the thing > done via the mlock*() system calls", but that is a nonsensical distinction > that actively and incorrectly ignores other system calls that can and do > pin memory legitimately. Nope. I have said that Memory pinning is done by increasing the refcount which is different from mlock which sets a page flag. I have consistently argued that these are two different things. And I am a bit surprised that this point has not been understood after all these repetitions. Memory pinning these days is done as a side effect of kernel / driver needs. I.e. the memory registration done through the IB subsystem and elsewhere. > int can_do_mlock(void) > { > if (capable(CAP_IPC_LOCK)) > return 1; > if (rlimit(RLIMIT_MEMLOCK) != 0) > return 1; > return 0; > } > EXPORT_SYMBOL(can_do_mlock); > > Q.E.D. Argh. Just checked the apps. True. They did set the rlimit to 0 at some point in order to make this work. Then they monitor the number of locked pages and create alerts so that action can be taking if a system uses too many mlocked pages. -- 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