Re: kern/45718: processes sometimes get stuck and spin in vm_map

[David Laight <david%l8s.co.uk@localhost>]

The following reply was made to PR kern/45718; it has been noted by GNATS.

From: David Laight <david%l8s.co.uk@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
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
 > Cc: 
 > 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
 
 -- 
 David Laight: david%l8s.co.uk@localhost