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Re: I/O permission bitmap patch for oskit-mach

From: Roland McGrath
Subject: Re: I/O permission bitmap patch for oskit-mach
Date: Sun, 10 Mar 2002 22:07:32 -0500 (EST)

> Do you think the performance increase is worth the memory overhead of a
> zone, esp if you preallocate iopb's (each being 8192 bytes huge)?

What memory overhead are you talking about?  The zone_t data structure is
just a few words.  The question is basically whether or not you have a free
list for fast allocation.  There is no unnecessary extra memory used,
because the free list is returned when memory is tight (ZONE_COLLECTABLE).
I'm not sure what you mean by "preallocate".  Yes, iopb's are allocated
whole or not at all, but tasks can come and go fast (hence struct task et al
have zones).

> New patch, for now without a zone for iopb's, at
> http://www.debian.org/~brinkmd/iopb-2002-03-11.patch

Go ahead and put it in if that exact code is tested and working.
You could change it to use zones first if you want to test that now,
or put it in first and add that later (but I still think we should do it).

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