Requirement for shm align maybe larger than 4KB (e.g. some number of MBytes). Another config for that ODP_CONFIG_SHM_ALIGN_MAX ?
-Petri From: ext Bill Fischofer [mailto:[email protected]] Sent: Tuesday, December 09, 2014 3:07 PM To: Savolainen, Petri (NSN - FI/Espoo) Cc: lng-odp-forward Subject: Re: [lng-odp] Alignment question The APIs that currently support alignment are odp_buffer_pool_create() and odp_shm_reserve() On Tue, Dec 9, 2014 at 7:03 AM, Bill Fischofer <[email protected]<mailto:[email protected]>> wrote: That makes sense. I'll add those additional CONFIG vars to the v3 patch. I don't see a use case for alignments above 4K for RAW buffers so that's a reasonable upper limit, however I suspect some implementations may have problems with that. If a platform has a HW buffer manager that uses 512 byte blocks, they are going to be 512-byte aligned and it's meaningless to try to ask for a higher alignment. On Tue, Dec 9, 2014 at 6:54 AM, Savolainen, Petri (NSN - FI/Espoo) <[email protected]<mailto:[email protected]>> wrote: From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of ext Bill Fischofer Sent: Tuesday, December 09, 2014 1:08 PM To: lng-odp-forward Subject: [lng-odp] Alignment question A number of APIs support a buf_align parameter but we haven't been terribly precise about limits on this, so some questions for Petri. I think only buffer_pool_create has alignment parameter. With buf_align being defined as uint32_t in theory we can specify alignments up to 2GB. 1. MAY implementations impose a lower upper limit on the alignments they support? ODP_CONFIG_BUFFER_ALIGN_MAX (4*1024) ? 2. If so, what is the minimum acceptable upper alignment limit? We've specified that buffers MUST be at minimum 8 byte aligned but is that sufficient? ODP_CONFIG_BUFFER_ALIGN_MIN 8 ? 3. If implementations MAY impose an upper alignment limit below 2GB, what SHOULD happen if an application requests an alignment above this limit? Fail the request? Saturate at the implementation-defined max alignment? It should fail. User requests minimum alignment, implementation can round up. -Petri
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