A MMAP observation

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From
Jaye Mathisen <mrcpu@cdsnet.net>
Date
16 May 1996 16:48:00
Subject
A MMAP observation
Message-ID
Pine.NEB.3.92.960516164342.24704t-100000@schizo.cdsnet.net


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I've been using MSQL a bit to play around with some stuff, and w/o
question, *disabling* mmap() in MSQL lets the application run much faster
than *with* mmap.

The DB is about 20MB's, and with MMAP (on a 64MB box), it pages a fair
amount, and the process gets way up there. W/o mmap, running the same
queries and such, the CPU time is way up there, but hardly any paging
activity.

It also seems to reach a steady state much quicker, where the
Wired/Cache/Buf/Free numbers hardly change.


I guess w/o more empirical evidence, what it says to me is that at first
run, the FreeBSD VM system is doing a darn good job, especially caching.

The same app run on BSD/OS just kills it. I don't know why, but there are
a few machine differences that may be coming in to play as well.

Of course, if somebody would make ODBC clients for FreeBSD so I could let
it talk to my NT SQL server, then I wouldn't have to mess with this at
all. :)



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