Re: [PATCH v2] MIPS64: Support of at least 48 bits of SEGBITS

[Leonid Yegoshin]

On 05/15/2015 02:53 PM, Ralf Baechle wrote:
> On Thu, May 14, 2015 at 06:34:43PM -0700, Leonid Yegoshin wrote:
>
> The order 1 allocation for the PGD are concerning me a little.  On a
> system under even moderate memory pressure that might become a bit of
> a reliability or performance issue.
>
> With 4kB pages we already need order 1 or even 2 allocations for the
> allocation of the stack and some folks have reported that to be an issue
> so we may have to start using the PUD for very large VA spaces.
>
>    Ralf

I don't think it is an issue here - people, who wants to exercise 256 
TERABAIT of memory PER PROCESS may even doesn't note that they have PGD 
= 2 pages. It is definitely not for systems with 4GB physmemory.

I also recommend for low memory to look into CONFIG_COMPACTION, it may 
be a great help for them here, look into mm/vmscan.c, 
in_reclaim_compaction().

Besides that, I defined this feature for 16KB and 64KB pages only, not 
for 4KB.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/