Not a problem, atm I'm happy about any review and comment :-)
Briefly - We had discussed non desktop scenarios where like a day load
that builds up the working set to 50% and a nightly backup job which
then is unable to use that protected 50% when sequentially reading a lot
of disks and due to that doesn't finish before morning.
The knob should help those people that know their system would suffer
from this or similar cases to e.g. set the protected ratio smaller or
even to zero if wanted.
As mentioned before, being able to gain back those protected 50% would
be even better - if it can be done in a way not hurting the original
intention of protecting them.
I personally just don't feel too good knowing that 50% of my memory
might hang around unused for many hours while they could be of some use.
I absolutely agree with the old intention and see how the patch helped
with the latency issue Elladan brought up in the past - but it just
looks way too aggressive to protect it "forever" for some server use cases.
The discussion ends at http://lkml.org/lkml/2010/4/22/38 - feel free to
click through it.
--
Grüsse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
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