svn commit: r243631 - in head/sys: kern sys

[Andre Oppermann]

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;