From owner-freebsd-arch Thu Nov 11 15:36:48 1999 Delivered-To: freebsd-arch@freebsd.org Received: from ns1.yes.no (ns1.yes.no [195.204.136.10]) by hub.freebsd.org (Postfix) with ESMTP id 2E85214F70 for ; Thu, 11 Nov 1999 15:36:39 -0800 (PST) (envelope-from eivind@bitbox.follo.net) Received: from bitbox.follo.net (bitbox.follo.net [195.204.143.218]) by ns1.yes.no (8.9.3/8.9.3) with ESMTP id AAA02836 for ; Fri, 12 Nov 1999 00:36:37 +0100 (CET) Received: (from eivind@localhost) by bitbox.follo.net (8.8.8/8.8.6) id AAA14368 for freebsd-arch@freebsd.org; Fri, 12 Nov 1999 00:36:36 +0100 (MET) Received: from nomis.simon-shapiro.org (nomis.simon-shapiro.org [209.86.126.163]) by hub.freebsd.org (Postfix) with SMTP id 9D02F14F4D for ; Thu, 11 Nov 1999 15:36:26 -0800 (PST) (envelope-from shimon@simon-shapiro.org) Received: (qmail 38325 invoked from network); 11 Nov 1999 23:36:25 -0000 Received: from localhost.simon-shapiro.org (HELO simon-shapiro.org) (127.0.0.1) by localhost.simon-shapiro.org with SMTP; 11 Nov 1999 23:36:25 -0000 Message-ID: <382B52F9.2C6D1E00@simon-shapiro.org> Date: Thu, 11 Nov 1999 18:36:25 -0500 From: Simon Shapiro Organization: Simon's Garage X-Mailer: Mozilla 4.6 [en] (X11; I; FreeBSD 3.3-STABLE i386) X-Accept-Language: en MIME-Version: 1.0 To: Randell Jesup Cc: freebsd-arch@freebsd.org Subject: Re: I/O Evaluation Questions (Long but interesting!) References: Content-Type: text/plain; charset= Content-Transfer-Encoding: 7bit Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Randell Jesup wrote: > > Simon Shapiro writes: > >> > We run circles around NT in the Random I/O department, > >> > but take a beating in the sequential I/O arena; > >> > For about the same hardware, they do 98 MB/Sec, > >> > I cannot get more than 45. > >> > >> I've always though FreeBSD has the opposite problem. > > > >Nope. I am getting 167MB/Sec for random block device. > >We are almost nine times faster on random WRITE (and I > >am comparing RAW I/O here to buffered there), twice as > >fast on random READ (again our RAW vs. their buffered. > > > >If you compare our block perfromance to theirs, we are > >almost fourty times faster. > > > >We are on-par on sequential WRITEs; we get 10MB/Sec RAW and > >14 block, they report under 20. > > > >There must be some nasty trick to their sequential READ; > >It is 5 times as fast as their sequential WRITE. > > It's really hard to comment without knowing exactly what > you were testing on each, and whether they really were equivalent tests. Of course you are right, but, at times, I come across info that is not to be quoted at the source. > First, are you certain they're not caching the data, even > if they're not supposed to be? This would be my #1 guess. AKAIK, you really have to be an NT kernel hacker to get raw i/o. > Second, could they be (for large IO's) transferring directly > into user memory, bypassing all buffers (I haven't really been following > the discussion; a good trick is to do direct DMA into the destination > buffer - it also allows you to use large commands to the drive (less > command overhead). Saving a memory-to-memory copy counts at those speeds. This happens in FreeBSD on raw I/O. I belive some work was done to do that on block i.o too (something to do with zero copy in vm... > Third, they could be doing some severe page table magic and not > actually reading most of the data into physical memory until it's accessed. Hard to do with the i2o protocol, as you give the IOP a S/G list and have no control from that point on... > Unlikely, though, and very tricky. (Interesting idea, though - > pseudo-mmap.) They also could set up the DMA, and mark the pages in the > page table so that you'll fault if you try to access them, and then undo > the mark when the IO is done (or as each N pages of the IO is done make > those N pages accessible). There are many cute tricks here... > > What hardware do you have that gives 100MB/s or more??? (bragging corner: 167 read, 138 write :-) DPT PM3755U2B with 256MB of ECC cache in a Dell PowerEdge 1300/600. FreeBSD RELENG_3, single CPU running. > -- > Randell Jesup, Worldgate Communications, ex-Scala, ex-Amiga OS team ('88-94) > rjesup@wgate.com > CDA II has been passed and signed, sigh. The lawsuit has been filed. Please > support the organizations fighting it - ACLU, EFF, CDT, etc. > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-arch" in the body of the message -- Sincerely Yours, Shimon@Simon-Shapiro.ORG 404.664.6401 Simon Shapiro Unwritten code has no bugs and executes at twice the speed of mouth To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message