From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="iso-8859-1" From: Hubertus Franke Reply-To: frankeh@watson.ibm.com Subject: Re: [PATCH] recognize MAP_LOCKED in mmap() call Date: Wed, 25 Sep 2002 11:36:08 -0400 References: In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <200209251136.08559.frankeh@watson.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Mark_H_Johnson@raytheon.com, Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, owner-linux-mm@kvack.org List-ID: On Wednesday 18 September 2002 03:18 pm, Mark_H_Johnson@raytheon.com wrote: > Andrew Morton wrote: > >(SuS really only anticipates that mmap needs to look at prior mlocks > >in force against the address range. It also says > > > > Process memory locking does apply to shared memory regions, > > > >and we don't do that either. I think we should; can't see why SuS > >requires this.) > > Let me make sure I read what you said correctly. Does this mean that Linux > 2.4 (or 2.5) kernels do not lock shared memory regions if a process uses > mlockall? > > If not, that is *really bad* for our real time applications. We don't want > to take a page fault while running some 80hz task, just because some > non-real time application tried to use what little physical memory we allow > for the kernel and all other applications. > > I asked a related question about a week ago on linux-mm and didn't get a > response. Basically, I was concerned that top did not show RSS == Size when > mlockall(MCL_CURRENT|MCL_FUTURE) was called. Could this explain the > difference or is there something else that I'm missing here? > > Thanks. > --Mark H Johnson > Sorry for the lengthy delay. mlock() and mlockall() do the right thing.. however, mmap(MAP_LOCKED) should behave like a mmap | mlock operation according to the manpages. This however was not implemented as the transformation from the mmap_flags to vm_flags never checked for MAP_LOCKED but only for mm->def_flags which only covers a previous mlockall() call. Hope this clarifies it . -- -- Hubertus Franke (frankeh@watson.ibm.com) -- 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/