Date: Thu, 29 Nov 2012 00:15:46 +0100 From: Andre Oppermann <andre@freebsd.org> To: Bruce Evans <brde@optusnet.com.au> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Alan Cox <alc@rice.edu> Subject: Re: svn commit: r243631 - in head/sys: kern sys Message-ID: <50B69B22.80706@freebsd.org> In-Reply-To: <20121129072617.T1123@besplex.bde.org> References: <201211272119.qARLJxXV061083@svn.freebsd.org> <50B64BE8.3040708@rice.edu> <20121129072617.T1123@besplex.bde.org>
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On 28.11.2012 22:45, Bruce Evans wrote:
> On Wed, 28 Nov 2012, Alan Cox wrote:
>
>> I'm pretty sure that the "realmem" calculation is going to overflow on
>> i386/PAE, where the number of bytes of physical memory is greater than
>> the type long can represent.
>
> It overflows on i386 even without PAE, where the number of bytes of
> physical memory is greater than the type long can represent (2GB). This is the usual case for new
> hardware.
Please have a look at the attached patch. Is quad_t the appropriate
type to use? If not, which is the right one?
> I think it changes the defaults for machines with small amounts of
> memory (say 32MB) in dangerous ways.
>
> Reserving half of kva for mbufs is network-centric. I reserve more
> than half of kva for the buffer cache in some configurations
> (VM_BCACHE_SIZE_MAX defaults too 200 MB, but I use 512 MB), and in the
> old scheme where the default for mbufs was under-sized, this may even
> have fitted without separate tuning for mbufs.
Please note that NO *reservations* are made for mbufs. It's only *limits*
that are enforced. For example stand-alone mbufs were not limited at all
previously and could completely exhaust all available kernel memory.
> The code has lots of style bugs.
Thank you for your detailed input. I'll handle that after the "long"
overflow issue is solved.
--
Andre
Index: kern/subr_param.c
===================================================================
--- kern/subr_param.c (revision 243631)
+++ kern/subr_param.c (working copy)
@@ -271,7 +271,7 @@
void
init_param2(long physpages)
{
- long realmem;
+ quad_t realmem;
/* Base parameters */
maxusers = MAXUSERS;
@@ -332,10 +332,10 @@
* available kernel memory (physical or kmem).
* At most it can be 3/4 of available kernel memory.
*/
- realmem = lmin(physpages * PAGE_SIZE,
+ realmem = qmin(physpages * PAGE_SIZE,
VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS);
maxmbufmem = realmem / 2;
- TUNABLE_LONG_FETCH("kern.maxmbufmem", &maxmbufmem);
+ TUNABLE_QUAD_FETCH("kern.maxmbufmem", &maxmbufmem);
if (maxmbufmem > (realmem / 4) * 3)
maxmbufmem = (realmem / 4) * 3;
Index: sys/mbuf.h
===================================================================
--- sys/mbuf.h (revision 243631)
+++ sys/mbuf.h (working copy)
@@ -395,7 +395,7 @@
*
* The rest of it is defined in kern/kern_mbuf.c
*/
-extern long maxmbufmem;
+extern quad_t maxmbufmem;
extern uma_zone_t zone_mbuf;
extern uma_zone_t zone_clust;
extern uma_zone_t zone_pack;
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