Date: Thu, 11 Nov 1999 23:15:00 -0500 From: Simon Shapiro <shimon@simon-shapiro.org> To: "Kenneth D. Merry" <ken@kdm.org> Cc: Randell Jesup <rjesup@wgate.com>, freebsd-arch@freebsd.org Subject: Re: I/O Evaluation Questions (Long but interesting!) Message-ID: <382B9444.44600C3@simon-shapiro.org> References: <199911120400.VAA31700@panzer.kdm.org>
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"Kenneth D. Merry" wrote:
>
> Simon Shapiro wrote...
> > "Kenneth D. Merry" wrote:
> > >
> > > [ Simon: the "charset = " (i.e. nothing) line your mail makes my mailer
> > > barf. You may want to adjust your character set. ]
> > [ Am using Netscape Messenger. Know not how to do that
> > (no relevant preference found :-( ]
>
> My best guess is, go to:
>
> Edit -> Preferences -> Navigator -> Languages
>
> And make sure you at least have English defined there. Also, go to:
>
> View -> Character Set
>
> And make sure you've got Western (ISO-8559-1) defined.
How's that? (sorry for the spam...)
> > > Simon Shapiro wrote...
> > > > Randell Jesup wrote:
> > > > > 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.
> > >
> > > How can you get speeds like that with just a 32-bit PCI bus? The specs for
> > > the PowerEdge 1300 say it has 5 32-bit PCI slots:
> >
> > These numbers are for block devices. The kernel obviously
> > caches some of this. I should look next time at emory usage;
> > The machine has 1GB of memory. The dataset is about 15GB per
> > array.
>
> Is that for random or sequential I/O? With sequential I/O, you would
> probably blow away any caching effects. With random I/O, though, you might
> get significant help from the cache, especially with that much RAM.
Random, of course.
To stay architectually minded, please consider these thoughts:
Increasing the workers load in this test increases measured
throughput (which is to be expected). However, past about
400 concurrent workers, performance declines rapidly.
At about 600 the system simply goes nuts. Processes exit
or hang solidly without any warnings.
Must be some resources to be increased. How is the
ftp.cdrom.com kernel configured? This may help me.
> > I am getting about 120MB/Sec form the PCI
> > bus.
>
> I can believe that.
>
> > Raw disks perfromance is totally throttled by physics;
> > We are running at about 200% of Seagate specs.
>
> How can you run at 200% of the spec? Most of the time disk manufacturers
> are even a little optimistic about their high end performance.
I suspect caching on the disk. I also know the DPT
firmware, while claiming not to do READ caching, does some
very interesting things with sorting, queuing, tagging, etc.
This is worth the difference. More or less.
BTW, I am not looking at claimed benchmarks from the mfgs.
I am looking at what tends to be accurately reported;
Sek times, internal transfer rates, data sheets timing
specs, etc.
> > I am running into some strange situations. Perhaps some
> > light can be shed;
>
> Sorry, no clue there.
:-( Holds me and a bunch others back.
> Ken
> --
> Kenneth Merry
> ken@kdm.org
--
Sincerely Yours, Shimon@Simon-Shapiro.ORG
404.664.6401
Simon Shapiro
Unwritten code has no bugs and executes at twice the speed of mouth
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