Re: [PATCH] Recent VM fiasco - fixed

From: Simon Kirby (
Date: Wed May 10 2000 - 20:53:01 EST

On Thu, May 11, 2000 at 03:04:37AM +0200, Juan J. Quintela wrote:

> >>>>> "linus" == Linus Torvalds <> writes:
> linus> Which makes the whole process much more streamlined, and makes the numbers
> linus> more repeatable. It also fixes the problem with dirty buffer cache data
> linus> much more efficiently than the kflushd approach, and mmap002 is not a
> linus> problem any more. At least for me.
> I have done my normal mmap002 test and this goes slower than
> ever, it takes something like 3m50 seconds to complete, (pre7-8 2m50,
> andrea classzone 2m8, and 2.2.15 1m55 for reference). I have no more
> time now to do more testing, I will continue tomorrow late. My
> findings are:
> real 3m41.403s
> user 0m16.010s
> sys 0m36.890s
> It takes the same user time than anterior versions, but the system
> time has aumented a lot, it was ~10/12 seconds in pre7-8 and around 8
> in classzone and 2.2.15.

I, too, see unbelievably slow writing now when uncompressing large data
files. 128 MB, dual processor, IDE drive. It seems to syncronously be
writing out data as it's dirty, not grouping it into blocks at all like
it used to. This would probably increase seeking, no?

Trying now with Andrea's classzone-27 against pre7-8, the results are
much better.

I attached vmstat-1.txt (2.3.99pre7-8+classzone-27) and vmstat-2.txt
(2.3.99pre7-9), which are outputs from "vmstat 1" when uncompressing the
same thing. 2.3.99pre7-9 seems to be taking about twice as long (real
time). This is from and to a 4K EXT2 filesystem. Both seem to swap out
some, which I guess is arguably good or bad...

Is Andrea taking a too dangerous approach for the current kernel version,
or are you trying to get something extremely simple working instead?


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