From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 18 Aug 2001 06:00:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 18 Aug 2001 06:00:11 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:41595 "EHLO flinx.biederman.org") by vger.kernel.org with ESMTP id ; Sat, 18 Aug 2001 06:00:03 -0400 To: Dan Hollis Cc: , David Christensen , Holger Lubitz , Subject: Re: Encrypted Swap In-Reply-To: From: ebiederm@xmission.com (Eric W. Biederman) Date: 18 Aug 2001 03:52:53 -0600 In-Reply-To: Message-ID: User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.5 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Dan Hollis writes: > On 17 Aug 2001, Eric W. Biederman wrote: > > Clearing memory on most machines takes a 1s or less. Think of memory > > fill rates at the 800MB/s level. Most BIOS's seem to clear some of > > the memory but I haven't read their code to see what they are doing. > > Ive measured rates far lower than that, at least for SDRAM. Hmm. The numbers were off the top of my head and I've been messing with DDR SDRAM quite a bit so I may have doubled it. Hmm. Nope. I was remember something close to the typical streams numbers on an Athlon with DDR SDRAM. Since those are read-modify-write numbers they should be close to the write numbers for normal SDRAM. With a PII/PIII and PC100 SDRAM I have measured about 640 MB/s writes. > http://bani.anime.net/memspeed/ However just looking at your numbers, I would guess that there is something off. Read numbers should almost always be worse then write numbers on SDRAM, because reads have a latency between the command and the first data cycle. Writes do not have that delay. Compare what you have to streams. But those numbers from Memtest.c don't look correct at all. Eric