On Mon, Jun 23, 2014 at 02:17:03PM +0100, Mark Salter wrote: > On Mon, 2014-06-23 at 12:09 +0100, Catalin Marinas wrote: > > My proposal (in the absence of any kind of description) is to still > > create a ZONE_DMA if we have DMA memory below 32-bit, otherwise just add > > everything (>32-bit) to ZONE_DMA. Basically an extension from your CMA > > patch, make dma_phys_limit static in that file and set it to > > memblock_end_of_DRAM() if no 32-bit DMA. Re-use it in the > > zone_sizes_init() function for ZONE_DMA (maybe with a pr_info for no > > 32-bit only DMA zone). > > There's a performance issue with all memory being in ZONE_DMA. It means > all normal allocations will fail on ZONE_NORMAL and then have to fall > back to ZONE_DMA. It would be better to put some percentage of memory > in ZONE_DMA.
Is the performance penalty real or just theoretical? I haven't run any benchmarks myself. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
