Date: Fri, 7 Apr 1995 20:51:32 +0800 (CST) From: Brian Tao <taob@gate.sinica.edu.tw> To: FREEBSD-CURRENT-L <freebsd-current@FreeBSD.org> Subject: Re: Label/slices : how to add a disk ? Message-ID: <Pine.BSI.3.91.950407202857.20266D-100000@aries.ibms.sinica.edu.tw> In-Reply-To: <199504070923.CAA07043@gndrsh.aac.dev.com>
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On Fri, 7 Apr 1995, Rodney W. Grimes wrote:
>
> This is on a 16MB machine, P54C-90, NCR810 controller iozone 2.01: The
> buffer cache become ineffective at 8MB transfer size, but still skewed
> the numbers some (~200K/sec).
[...]
> Writing the 128 Megabyte file, 'iozone.tmp'...53.343750 seconds
> Reading the file...51.906250 seconds
>
> IOZONE performance measurements:
> 2516090 bytes/second for writing the file
> 2585772 bytes/second for reading the file
How much CPU is being eaten on your machine while performing the
benchmark? My machine is a PCI 486DX4/100 machine (16 megs) with the
NCR53810 controller and a Quantum Empire 1080. iozone 2.01:
IOZONE writes a 128 Megabyte sequential file consisting of
16384 records which are each 8192 bytes in length.
It then reads the file. It prints the bytes-per-second
rate at which the computer can read and write files.
Writing the 128 Megabyte file, 'iozone.tmp'...44.750000 seconds
Reading the file...43.953125 seconds
IOZONE performance measurements:
2999278 bytes/second for writing the file
3053656 bytes/second for reading the file
'top' shows this (sometime during the latter half of the run):
PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
20444 root 48 0 244K 424K run 0:41 51.76% 50.35% iozone
Is this a reasonable figure? At 3000000 bytes/sec using 8192-byte
blocks, the CPU is shuttling about 366 I/O operations a second or
about 2.7 ms per operation. That sounds like "a lot of time" from a
CPU's viewpoint, most of it spent waiting for the disk (I assume?).
BTW, out of curiosity, if I do something like this:
% time dd if=/dev/zero of=/dev/null bs=102400 count=10240
10240+0 records in
10240+0 records out
1048576000 bytes transferred in 30 secs (34952533 bytes/sec)
0.171u 28.688s 0:29.33 98.3% 56+529k 0+1io 0pf+0w
... just what am I measuring? CPU-to-RAM bandwidth? CPU-to-cache
speed? Or nothing at all useful? :)
--
Brian ("Though this be madness, yet there is method in't") Tao
taob@gate.sinica.edu.tw <-- work ........ play --> taob@io.org
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