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SubjectRe: Since no one else has stepped forward: 'ZeroD' patch
   From: Jes Degn Soerensen <>
Date: 09 Jan 1997 13:30:28 +0100

Zerod may also be a bad idea for other small-cache architectures
such as the sun4c - but I'm not sure about this, guess one of the
Sparc hackers will be better to answer this one.

Sun4c has 64k pure virtual cache, it gets flushed so frequently just
do to the fact that it is pure virtual that zerod cannot make things
any worse. Most of the sun4m caches are either 8k to 16k a piece of
split I/D pure physical caches, most have some huge 1MB of so
L2 cache sitting underneath.

Therefore I think it might be a good idea to make zerod a
config-option or at least an option to disable it?

If this is truly idle time in which zerod is running, and as you
mention you have the 256byte caches, anyone doing quick sleeps and the
processing for the device driver performing the "event" it is waiting
for is going to blow the tasks resident set anyways (I see this on
MicroSparc's with 4k data caches as well, any sleep loses your
resident set in the cache completely no matter how small the data
being touched by the processing is for the sleep nor how short the
time you go to sleep is)

Yow! 11.26 MB/s remote host TCP bandwidth & ////
199 usec remote TCP latency over 100Mb/s ////
ethernet. Beat that! ////
-----------------------------------------////__________ o
David S. Miller, /_____________/ / // /_/ ><

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