On 2015/10/9 17:24, Kamezawa Hiroyuki wrote: > On 2015/10/09 15:46, Xishi Qiu wrote: >> On 2015/10/9 22:56, Taku Izumi wrote: >> >>> Xeon E7 v3 based systems supports Address Range Mirroring >>> and UEFI BIOS complied with UEFI spec 2.5 can notify which >>> ranges are reliable (mirrored) via EFI memory map. >>> Now Linux kernel utilize its information and allocates >>> boot time memory from reliable region. >>> >>> My requirement is: >>> - allocate kernel memory from reliable region >>> - allocate user memory from non-reliable region >>> >>> In order to meet my requirement, ZONE_MOVABLE is useful. >>> By arranging non-reliable range into ZONE_MOVABLE, >>> reliable memory is only used for kernel allocations. >>> >> >> Hi Taku, >> >> You mean set non-mirrored memory to movable zone, and set >> mirrored memory to normal zone, right? So kernel allocations >> will use mirrored memory in normal zone, and user allocations >> will use non-mirrored memory in movable zone. >> >> My question is: >> 1) do we need to change the fallback function? > > For *our* requirement, it's not required. But if someone want to prevent > user's memory allocation from NORMAL_ZONE, we need some change in zonelist > walking. > Hi Kame, So we assume kernel will only use normal zone(mirrored), and users use movable zone(non-mirrored) first if the memory is not enough, then use normal zone too. >> 2) the mirrored region should locate at the start of normal >> zone, right? > > Precisely, "not-reliable" range of memory are handled by ZONE_MOVABLE. > This patch does only that. I mean the mirrored region can not at the middle or end of the zone, BIOS should report the memory like this, e.g. BIOS node0: 0-4G mirrored, 4-8G mirrored, 8-16G non-mirrored node1: 16-24G mirrored, 24-32G non-mirrored OS node0: DMA DMA32 are both mirrored, NORMAL(4-8G), MOVABLE(8-16G) node1: NORMAL(16-24G), MOVABLE(24-32G) > >> >> I remember Kame has already suggested this idea. In my opinion, >> I still think it's better to add a new migratetype or a new zone, >> so both user and kernel could use mirrored memory. > > Hi, Xishi. > > I and Izumi-san discussed the implementation much and found using "zone" > is better approach. > > The biggest reason is that zone is a unit of vmscan and all statistics and > handling the range of memory for a purpose. We can reuse all vmscan and > information codes by making use of zones. Introdcing other structure will be messy. Yes, add a new zone is better, but it will change much code, so reuse ZONE_MOVABLE is simpler and easier, right? > His patch is very simple. > The following plan sounds good to me. Shall we rename the zone name when it is used for mirrored memory, "movable" is a little confusion. > For your requirements. I and Izumi-san are discussing following plan. > > - Add a flag to show the zone is reliable or not, then, mark ZONE_MOVABLE as not-reliable. > - Add __GFP_RELIABLE. This will allow alloc_pages() to skip not-reliable zone. > - Add madivse() MADV_RELIABLE and modify page fault code's gfp flag with that flag. > like this? user: madvise()/mmap()/or others -> add vma_reliable flag -> add gfp_reliable flag -> alloc_pages kernel: use __GFP_RELIABLE flag in buddy allocation/slab/vmalloc... Also we can introduce some interfaces in procfs or sysfs, right? Thanks, Xishi Qiu > > Thanks, > -Kame > > > > > > > > > > > > > > > > > > > > > > > . > -- 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>