Subject: Re: kernel map entry merging and PR 24039
To: YAMAMOTO Takashi <>
From: Andrew Brown <>
List: tech-kern
Date: 12/02/2004 09:04:49
On Thu, Dec 02, 2004 at 03:22:22PM +0900, YAMAMOTO Takashi wrote:
>> >> >i still think disabling entry merging (or, not to free memory for
>> >> >merged entries, at least) is a "real" fix because it's a design flaw
>> >> >to require memory allocation to free memory.
>> >> 
>> >> you can call it a design flaw if you want to, but imho it's more of a
>> >> flaw to consume more memory up front simply so that you don't have to
>> >> allocate it later.
>> >
>> >reserving memory for later use is a common practice.
>> >it's far better than relying upon pure luck.
>> reserving memory is fine.
>> rampantly allocating map entries (which happens when merging is
>> disabled) so that you'll never need to allocate a new one in order to
>> free is not quite the same thing.
>can you explain what's an important difference?  thanks.

using up memory is simply not the same as reserving it.  reserved
memory can be used for something at a later point in time.  used
memory cannot.

imho, using 2000 instead of 200 (or even 20) map entries cannot be
considered a reaonable solution to any problem.  unless the problem is
that you have too much ram.  :)

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