From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 25 Sep 2000 18:02:18 +0200 (CEST) From: Ingo Molnar Reply-To: mingo@elte.hu Subject: Re: the new VMt In-Reply-To: <20000925174138.D25814@athlon.random> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: Alan Cox , Marcelo Tosatti , Linus Torvalds , Rik van Riel , Roger Larsson , MM mailing list , linux-kernel@vger.kernel.org List-ID: On Mon, 25 Sep 2000, Andrea Arcangeli wrote: > Ingo's point is that the underlined line won't ever happen in the > first place please dont misinterpret my point ... Frankly, how often do we allocate multi-order pages? I've just made quick statistics wrt. how allocation orders are distributed on a more or less typical system: (ALLOC ORDER) 0: 167081 1: 850 2: 16 3: 25 4: 0 5: 1 6: 0 7: 2 8: 13 9: 5 ie. 99.45% of all allocations are single-page! 0.50% is the 8kb task-structure. The rest is 0.05%. i'm not talking about 4MB contiguous physical allocations having to succeed on a 8MB box. I'm talking about 99% of the simple allocation points not having to worry about a NULL pointer. (not checking for NULL is one of the most common allocation-related bug that beats low-RAM systems.) Ingo -- 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.eu.org/Linux-MM/