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Re: kern/45718: processes sometimes get stuck and spin in vm_map
The following reply was made to PR kern/45718; it has been noted by GNATS.
From: David Laight <david%l8s.co.uk@localhost>
Subject: Re: kern/45718: processes sometimes get stuck and spin in vm_map
Date: Sun, 9 Dec 2012 18:22:22 +0000
On Sun, Dec 09, 2012 at 08:45:03AM +0000, Taylor R Campbell wrote:
> The following reply was made to PR kern/45718; it has been noted by GNATS.
> From: Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
> To: gnats-bugs%NetBSD.org@localhost
> Subject: Re: kern/45718: processes sometimes get stuck and spin in vm_map
> Date: Sun, 9 Dec 2012 08:43:58 +0000
> pmap(8) on the kernel_map (`pmap -V 0x87654321' with the address of
> kernel_map as shown by crash(8)) shows that kva is fragmented enough
> that there is indeed no empty space of at least #x40000 bytes, and
> that every request to exec_pool requiring a new kva allocation is
> guaranteed to fail.
Allocating 256k blocks has to be sub-optimal!
Especially for something that is going to be chopped into pieces
(which is what I suspect is happening here).
Personally I've no idea why we have this large proliferation of
memory 'pools' - rather than just allocating items as-needed from
general free lists.
There might be some mileage in keeping stats for some uses - and
predetermining the correct list for fixed size items - but not
big private memory free lists.
David Laight: david%l8s.co.uk@localhost
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