Messages in this thread | | | Subject | Re: [PATCH 1/6] sparc64: Add FORCE_MAX_ZONEORDER and default to 13 | From | tndave <> | Date | Mon, 24 Oct 2016 11:31:14 -0700 |
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On 10/24/2016 10:45 AM, David Miller wrote: > From: Tushar Dave <tushar.n.dave@oracle.com> > Date: Mon, 10 Oct 2016 11:12:02 -0700 > >> From: Dave Kleikamp <dave.kleikamp@oracle.com> >> >> This change allows ATU (new IOMMU) in SPARC systems to request >> large (32M) contiguous memory during boot for creating IOTSB backing >> store. >> >> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> >> Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com> > > If you need 32MB allocations, wouldn't a max zone order of 12 be > sufficient? (8K << 12 == 32MB) Yes, but config FORCE_MAX_ZONEORDER is actually maximum order plus one. For example, a value of 13 means that the largest free memory block is 2^12 pages. For 32MB we need 2^12 8K pages, hence FORCE_MAX_ZONEORDER must be MAX_ORDER + 1 i.e. 13.
Thanks.
-Tushar
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