4.2 scheduler

[Stanley Friesen]

In article <1360 at wanginst.UUCP> tupper at wanginst.UUCP (John Tupper) writes:
>
>We (not Wang Institute, a different we) recently switched from BSD 4.1 to
>BSD 4.2. We have found 4.2 to be SLOWER than 4.1 by alot!
>
>As far as I know we have the original 4.2 (have there been updates?).
>
>Any help on the following questions would be appreciated.
>
>	Has anyone else experienced the same thing (and what did
>	you do about it).

	Yes, it happened here too, and there is little that can be
done except hope that 4.3 becomes available soon, since 4.3 is
essentially 4.2 with *significant* speed improvements.
>
>	Are the different releases (updates) of 4.2?

	As far as i know the only "update" is to 4.3, which is only in
Beta testing right now.
>
>	Is there any tuning we can perform to the kernel to speed
>	things up?
>
	I doubt it, at least not significantly. The problem is *not*
the scheduler, it is a rather inefficient implementation of a number
of system services. The critical routine 'namei' is quite slow, due to
the need to recognise and correctly handle sockets. Also pipes now
have a few more layers of software to run them. Some of the
bookkeeping operations for the new Fast File System are rather CPU
intensive. The net result is that a 4.2 system spends 30 to 50% of
its time in the kernel(verify this by running vmstat)!! This is quite
high. As I understand it 4.3 has corrected many of these problems.

-- 

				Sarima (Stanley Friesen)

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