From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 1/1] MM: virtual address debug Date: Wed, 18 Jun 2008 22:51:02 +1000 References: <1213271800-1556-1-git-send-email-jirislaby@gmail.com> In-Reply-To: <1213271800-1556-1-git-send-email-jirislaby@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200806182251.02486.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Jiri Slaby Cc: Ingo Molnar , tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andi Kleen List-ID: On Thursday 12 June 2008 21:56, Jiri Slaby wrote: > Add some (configurable) expensive sanity checking to catch wrong address > translations on x86. > > - create linux/mmdebug.h file to be able include this file in > asm headers to not get unsolvable loops in header files > - __phys_addr on x86_32 became a function in ioremap.c since > PAGE_OFFSET, is_vmalloc_addr and VMALLOC_* non-constasts are undefined > if declared in page_32.h Uh, I have to disagree with this. __phys_addr is used in some really performance critical parts of the kernel, and the function calls are free mindset is just wrong. Even for modern x86 CPUs, the function call return might take 10 cycles or more when you include all costs. And for something like this #define __phys_addr(x) ((x) - PAGE_OFFSET) the code to call the function is probably bigger than inline generated code anyway. -- 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