Messages in this thread | | | Date | Fri, 15 May 2015 15:39:54 -0700 | From | Leonid Yegoshin <> | Subject | Re: [PATCH v2] MIPS64: Support of at least 48 bits of SEGBITS |
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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.
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