From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: Non-Contiguous Memory Allocation Tests Message-ID: From: Mark_H_Johnson@Raytheon.com Date: Wed, 10 Dec 2003 08:42:15 -0600 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Ruthiano Simioni Munaretti Cc: linux-mm@kvack.org, owner-linux-mm@kvack.org, sisopiii-l@cscience.org List-ID: >In VGNCA, the main idea is enable/disable interrupts only one time, reducing >this overhead. Also, VGNCA allocation/deallocation functions are a little >more simple, because elimination of unnecessary test conditions in size >allocation. > >Our patch is intended to be a test to check if this could bring enough >benefits to deserve a more careful implementation. We also included some code >to benchmark allocations and deallocations, using the RDTSC instruction. My only comment about this (and similar "optimizations") is a general concern about latency. Let's say I have an interactive (or real time) program running and some other application does one of these non contiguous memory allocations. Is the time to complete the allocation bounded? Not apparently since "numpages" is an input to the allocation routine. There also does not appear to be any code to allow a reschedule to occur if scheduling is needed. If you are serious about pursuing something like this, I suggest you review the lock break / preemption code in the kernel (or in Andrew Morton's low latency patches) for examples of the required coding style. --Mark H Johnson -- 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: aart@kvack.org