open() speed (was Blocking for disk I/O)

[Chris Torek]

>>Article <8295 at june.cs.washington.edu>, from ka at june.cs.washington.edu:
[1000 open() calls]
>>>	17.3 real    0.0 user    3.2 sys

In article <17643 at mimsy.UUCP> I wrote:
>>	% time ./t
>>	0.1u 0.9s 0:01 84% 1+3k 0+0io 2pf+0w
>>
>>4.3BSD > Ultrix ... ?

In article <2491 at shlump.dec.com> thomas at mipsbx.nac.dec.com (Matt Thomas)
replies:
>Hard to say, as no clue was given to the type of machine and/or disks.

True.

>    VAX 6220 (Ultrix V3.0, RA82):  0.0u 1.1s 0:00 120% 1+5k 0+1io 0pf+0w
>    DS3100 (Ultrix V3.1, RZ23):    0.0u 0.2s 0:00 100% 10+21k 0+0io 0pf+0w
>    uVAX II (Ultrix V3.0, RA81):   0.0u 2.8s 0:02 100% 1+5k 0+0io 0pf+0w
>    VAX 8700 (Ultrix V3.1, RA81):  0.0u 0.5s 0:00 83% 1+5k 0+0io 0pf+0w
>
>Which are rougly equivalent to the BSD 4.3 numbers.  When running over NFS,
>things really slow down.   
>
> VAX 8700 (Ultrix V3.1, RA81+NFS): 0.0u 1.8s 0:07 26% 2+6k 0+0io 0pf+0w

To fill in the missing details:

   VAX 11/785 (4.3BSD-tahoe, RA81): 0.1u 0.9s 0:01 84% 1+3k 0+0io 2pf+0w

An 11/780 is supposed to be `pretty close' to a MicroVAX II, and
an 11/785 is supposed to be `about' 50% faster.  Scaling the Ultrix
`1+5k' by 1/1.5 gives an expected sys (`s') time of 1.86..., not the
0.9 observed.  Apparently name lookups in 4.3BSD-tahoe have somewhat
less overhead than those in Ultrix 3.0.  (The cost may go up again
in 4.4 as a consequence of GVFS.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris