Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> writes: >> >> > Conceptually it would be cleaner, if expensive, to calculate the real >> > memblock reserves if HASH_EARLY and ditch the dma_reserve, memory_reserve >> > and nr_kernel_pages entirely. >> >> Why is it expensive? memblock tracks the totals for all memory and >> reserved memory AFAIK, so it should just be a case of subtracting one >> from the other? > > Are you suggesting that we use something like > memblock_phys_mem_size() but one which returns > memblock.reserved.total_size ? Maybe a new function like > memblock_reserved_mem_size()? Yeah, something like that. I'm not sure if it actually needs a function, AFAIK you can just look at the structure directly. >> > Unfortuantely, aside from the calculation, >> > there is a potential cost due to a smaller hash table that affects everyone, >> > not just ppc64. >> >> Yeah OK. We could make it an arch hook, or controlled by a CONFIG. > > If its based on memblock.reserved.total_size, then should it be arch > specific? Yes I think so. Otherwise you have to test it on every architecture :) >> > However, if the hash table is meant to be sized on the >> > number of available pages then it really should be based on that and not >> > just a made-up number. >> >> Yeah that seems to make sense. >> >> The one complication I think is that we may have memory that's marked >> reserved in memblock, but is later freed to the page allocator (eg. >> initrd). > > Yes, this is a possibility, for example lets say we want fadump to > continue to run instead of rebooting to a new kernel as it does today. But that's a bad idea and no one should ever do it. For starters all your caches will be undersized, and anything that is allocated per-node early in boot will not be allocated on the nodes which were reserved, so the system's performance will potentially differ from a normal boot in weird and unpredictable ways. cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>