From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 17 Nov 2008 13:31:37 -0800 From: Andrew Morton Subject: Re: Large stack usage in fs code (especially for PPC64) Message-Id: <20081117133137.616cf287.akpm@linux-foundation.org> In-Reply-To: References: <20081117130856.92e41cd3.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: rostedt@goodmis.org, linux-kernel@vger.kernel.org, paulus@samba.org, benh@kernel.crashing.org, linuxppc-dev@ozlabs.org, mingo@elte.hu, tglx@linutronix.de, linux-mm@kvack.org List-ID: On Mon, 17 Nov 2008 13:23:23 -0800 (PST) Linus Torvalds wrote: > > > On Mon, 17 Nov 2008, Andrew Morton wrote: > > > > Far be it from me to apportion blame, but THIS IS ALL LINUS'S FAULT!!!!! :) > > > > I fixed this six years ago. See http://lkml.org/lkml/2002/6/17/68 > > Btw, in that thread I also said: > > "If we have 64kB pages, such architectures will have to have a bigger > kernel stack. Which they will have, simply by virtue of having the very > same bigger page. So that problem kind of solves itself." > > and that may still be the "right" solution - if somebody is so insane that > they want 64kB pages, then they might as well have a 64kB kernel stack as > well. I'd have thought so, but I'm sure we're about to hear how important an optimisation the smaller stacks are ;) > Trust me, the kernel stack isn't where you blow your memory with a 64kB > page. You blow all your memory on the memory fragmentation of your page > cache. I did the stats for the kernel source tree a long time ago, and I > think you wasted something like 4GB of RAM with a 64kB page size. > Yup. That being said, the younger me did assert that "this is a neater implementation anyway". If we can implement those loops without needing those on-stack temporary arrays then things probably are better overall. -- 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