linux-kernel - Re: [PATCH] NOMMU: Separate out VMAs

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Message-ID: <46C58B4E.4080803@t-online.de>
Date:	Fri, 17 Aug 2007 13:49:34 +0200
From:	Bernd Schmidt <bernds_cb1@...nline.de>
To:	David Howells <dhowells@...hat.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Wu, Bryan" <Bryan.Wu@...log.com>
Subject: Re: [PATCH] NOMMU: Separate out VMAs

David Howells wrote:
> David Howells <dhowells@...hat.com> wrote:
> 
>> Yes.  I found the major leak this morning.  There may be a minor leak, but I'm
>> not convinced it's in the mmap stuff.  See revised patch.
> 
> Oops.  That was the old patch.  Try this one instead.
> 

Here are some changes to make it more stable on my system.  In 
do_mmap_private, I've commented out the logic to free excess pages, as 
it fragments terribly and causes a simple
  while true; do cat /proc/buddyinfo; done
loop to go oom.  Also, I think you're freeing high-order pages unaligned 
to their order?
In shrink_vma, we must save the mm across calls to remove_vma_from_mm 
(oops when telnetting into the box).
In do_munmap, we can deal with freeing more than one vma.  I've not 
touched the rb-tree logic in the shared file case, as I have no idea 
what it's trying to do given that only exact matches are allowed.

It still does not survive my mmap stress-tester, so I'll keep looking.

Why do we need vm_regions for anonymous memory?  Wouldn't it be enough 
to just have a VMA?

Bernd
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