Re: pre6 VM issues

Date: Tue Oct 09 2001 - 09:37:19 EST

Marcelo Tosatti wrote:

>On Tue, 9 Oct 2001, BALBIR SINGH wrote:
>>Most of the traditional unices maintained a pool for each subsystem
>>(this is really useful when u have the memory to spare), so not matter
>>what they use memory only from their pool (and if needed peek outside),
>>but nobody else used the memory from the pool.
>>I have seen cases where, I have run out of physical memory on my system,
>>so I try to log in using the serial console, but since the serial driver
>>does get_free_page (this most likely fails) and the driver complains back.
>>So, I had suggested a while back that important subsystems should maintain
>>their own pool (it will take a new thread to discuss the right size of
>>each pool).
>>Why can't Linux follow the same approach? especially on systems with a lot
>>of memory.
>There is nothing which avoids us from doing that (there is one reserved
>pool I remeber right now: the highmem bounce buffering pool, but that one
>is a special case due to the way Linux does IO in high memory and its only
>needed on _real_ emergencies --- it will be removed in 2.5, I hope).
>In general, its a better approach to share the memory and have a unified
>pool. If a given subsystem is not using its own "reversed" memory, another
>subsystems can use it.
>The problem we are seeing now can be fixed even without the reserved
I agree that is the fair and nice thing to do, but I was talking about reserving
memory for device vs sharing it with a user process, user processes can wait,
their pages can even be swapped out if needed. But for a device that is not willing
to wait (GFP_ATOMIC) say in an interrupt context, this might be a issue.

Anyway, how do you plan to solve this ?

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