On 6 January 2017 at 01:07, Hanjun Guo <hanjun.guo@xxxxxxxxxx> wrote: > On 2017/1/5 10:03, Hanjun Guo wrote: >> >> On 2017/1/4 21:56, Ard Biesheuvel wrote: >>> >>> On 16 December 2016 at 16:54, Robert Richter <rrichter@xxxxxxxxxx> wrote: >>>> >>>> On ThunderX systems with certain memory configurations we see the >>>> following BUG_ON(): >>>> >>>> kernel BUG at mm/page_alloc.c:1848! >>>> >>>> This happens for some configs with 64k page size enabled. The BUG_ON() >>>> checks if start and end page of a memmap range belongs to the same >>>> zone. >>>> >>>> The BUG_ON() check fails if a memory zone contains NOMAP regions. In >>>> this case the node information of those pages is not initialized. This >>>> causes an inconsistency of the page links with wrong zone and node >>>> information for that pages. NOMAP pages from node 1 still point to the >>>> mem zone from node 0 and have the wrong nid assigned. >>>> >>>> The reason for the mis-configuration is a change in pfn_valid() which >>>> reports pages marked NOMAP as invalid: >>>> >>>> 68709f45385a arm64: only consider memblocks with NOMAP cleared for >>>> linear mapping >>>> >>>> This causes pages marked as nomap being no longer reassigned to the >>>> new zone in memmap_init_zone() by calling __init_single_pfn(). >>>> >>>> Fixing this by implementing an arm64 specific early_pfn_valid(). This >>>> causes all pages of sections with memory including NOMAP ranges to be >>>> initialized by __init_single_page() and ensures consistency of page >>>> links to zone, node and section. >>>> >>> >>> I like this solution a lot better than the first one, but I am still >>> somewhat uneasy about having the kernel reason about attributes of >>> pages it should not touch in the first place. But the fact that >>> early_pfn_valid() is only used a single time in the whole kernel does >>> give some confidence that we are not simply moving the problem >>> elsewhere. >>> >>> Given that you are touching arch/arm/ as well as arch/arm64, could you >>> explain why only arm64 needs this treatment? Is it simply because we >>> don't have NUMA support there? >>> >>> Considering that Hisilicon D05 suffered from the same issue, I would >>> like to get some coverage there as well. Hanjun, is this something you >>> can arrange? Thanks >> >> >> Sure, we will test this patch with LTP MM stress test (which triggers >> the bug on D05), and give the feedback. > > > a update here, tested on 4.9, > > - Applied Ard's two patches only > - Applied Robert's patch only > > Both of them can work fine on D05 with NUMA enabled, which means > boot ok and LTP MM stress test is passed. > Thanks a lot Hanjun. Any comments on the performance impact (including boot time) ? -- 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>