svn commit: r251586 - head/sys/arm/ti

[Olivier Houchard]

On Mon, Jun 10, 2013 at 10:37:36PM +0300, Konstantin Belousov wrote:
> On Mon, Jun 10, 2013 at 12:02:20PM -0500, Alan Cox wrote:
> > On 06/10/2013 06:08, Olivier Houchard wrote:
> > > On Mon, Jun 10, 2013 at 06:55:47AM +0300, Konstantin Belousov wrote:
> > >> On Sun, Jun 09, 2013 at 10:51:12PM +0000, Olivier Houchard wrote:
> > >>> Author: cognet
> > >>> Date: Sun Jun  9 22:51:11 2013
> > >>> New Revision: 251586
> > >>> URL: http://svnweb.freebsd.org/changeset/base/251586
> > >>>
> > >>> Log:
> > >>>   Increase the maximum KVM available on TI chips. Not sure why we suddenly need
> > >>>   that much, but that lets me boot with 1GB of RAM.
> > >> I suspect that the cause is the combination of limited KVA and
> > >> lack of any limitation for the buffer map. I noted that ARM lacks
> > >> VM_BCACHE_SIZE_MAX after a report from mav about similar (?) problem a
> > >> day ago.
> > >>
> > >> In essence, the buffer map is allowed to take up to ~330MB when no
> > >> upper limit from VM_BCACHE_SIZE_MAX is specified.
> > >
> > > Hi Konstantin,
> > >
> > > Thanks for the hint !
> > > It seems only i386 and sparc64 sets it, what would be a good value, 200M, as
> > > it is on i386 ?
> > >
> > 
> > Since there are many arm platforms with less than 1 GB of kernel virtual
> > address (KVA) space, VM_BCACHE_SIZE_MAX should be made to scale down
> > from 200 MB with the available KVA space.  See how VM_KMEM_SIZE_MAX is
> > currently defined on arm.
> 
> In fact, Ithink it does not make much sense to scale the buffer cache up.
> It is mostly wasted space now.  As I measured it, on typical load you
> have only 10-20% of instantiated buffers mapped.
> 
> Alexander Motin reported that he tested the equivalent of the following
> change.  With it committed, I think that r251586 could be reverted.
> 
> diff --git a/sys/arm/include/param.h b/sys/arm/include/param.h
> index 9ffb118..5c738c2 100644
> --- a/sys/arm/include/param.h
> +++ b/sys/arm/include/param.h
> @@ -128,6 +128,11 @@
>  #define USPACE_SVC_STACK_BOTTOM		(USPACE_SVC_STACK_TOP - 0x1000)
>  #define USPACE_UNDEF_STACK_TOP		(USPACE_SVC_STACK_BOTTOM - 0x10)
>  #define USPACE_UNDEF_STACK_BOTTOM	(FPCONTEXTSIZE + 10)
> +
> +#ifndef VM_BCACHE_SIZE_MAX
> +#define	VM_BCACHE_SIZE_MAX	(128 * 1024 * 1024)
> +#endif
> +
>  /*
>   * Mach derived conversion macros
>   */


I tested it with my changes reverted and it works indeed, so I'm fine with
this being committed and my changes being reverted.

Regards,

Olivier