On 10/20/2015 03:53 PM, Dave Hansen wrote: > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > I have a hugetlbfs user which is never explicitly allocating huge pages > with 'nr_hugepages'. They only set 'nr_overcommit_hugepages' and then let > the pages be allocated from the buddy allocator at fault time. > > This works, but they noticed that mbind() was not doing them any good and > the pages were being allocated without respect for the policy they > specified. > > The code in question is this: > >> > struct page *alloc_huge_page(struct vm_area_struct *vma, > ... >> > page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg); >> > if (!page) { >> > page = alloc_buddy_huge_page(h, NUMA_NO_NODE); > dequeue_huge_page_vma() is smart and will respect the VMA's memory policy. > But, it only grabs _existing_ huge pages from the huge page pool. If the > pool is empty, we fall back to alloc_buddy_huge_page() which obviously > can't do anything with the VMA's policy because it isn't even passed the > VMA. > > Almost everybody preallocates huge pages. That's probably why nobody has > ever noticed this. Looking back at the git history, I don't think this > _ever_ worked from when alloc_buddy_huge_page() was introduced in 7893d1d5, > 8 years ago. > > The fix is to pass vma/addr down in to the places where we actually call in > to the buddy allocator. It's fairly straightforward plumbing. This has > been lightly tested. > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Hey Dave, Trinity seems to be able to hit the newly added warnings pretty easily: [ 339.282065] WARNING: CPU: 4 PID: 10181 at mm/hugetlb.c:1520 __alloc_buddy_huge_page+0xff/0xa80() [ 339.360228] Modules linked in: [ 339.360838] CPU: 4 PID: 10181 Comm: trinity-c291 Not tainted 4.3.0-rc6-next-20151022-sasha-00040-g5ecc711-dirty #2608 [ 339.362629] ffff88015e59c000 00000000e6475701 ffff88015e61f9a0 ffffffff9dd3ef48 [ 339.363896] 0000000000000000 ffff88015e61f9e0 ffffffff9c32d1ca ffffffff9c7175bf [ 339.365167] ffffffffabddc0c8 ffff88015e61faf0 0000000000000000 ffffffffffffffff [ 339.366387] Call Trace: [ 339.366831] [<ffffffff9dd3ef48>] dump_stack+0x4e/0x86 [ 339.367648] [<ffffffff9c32d1ca>] warn_slowpath_common+0xfa/0x120 [ 339.368635] [<ffffffff9c7175bf>] ? __alloc_buddy_huge_page+0xff/0xa80 [ 339.369631] [<ffffffff9c32d3ca>] warn_slowpath_null+0x1a/0x20 [ 339.370574] [<ffffffff9c7175bf>] __alloc_buddy_huge_page+0xff/0xa80 [ 339.371551] [<ffffffff9c7174c0>] ? return_unused_surplus_pages+0x120/0x120 [ 339.372698] [<ffffffff9dda0327>] ? debug_smp_processor_id+0x17/0x20 [ 339.373683] [<ffffffff9c41574b>] ? get_lock_stats+0x1b/0x80 [ 339.374551] [<ffffffff9c42e901>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20 [ 339.375744] [<ffffffff9c433870>] ? do_raw_spin_unlock+0x1d0/0x1e0 [ 339.376728] [<ffffffff9c718333>] hugetlb_acct_memory+0x193/0x990 [ 339.377663] [<ffffffff9c7181a0>] ? dequeue_huge_page_node+0x260/0x260 [ 339.378658] [<ffffffff9c41c970>] ? trace_hardirqs_on_caller+0x540/0x5e0 [ 339.379671] [<ffffffff9c71e469>] hugetlb_reserve_pages+0x229/0x330 [ 339.380738] [<ffffffff9cba273b>] hugetlb_file_setup+0x54b/0x810 [ 339.381689] [<ffffffff9cba21f0>] ? hugetlbfs_fallocate+0x9e0/0x9e0 [ 339.382653] [<ffffffff9dd669f0>] ? scnprintf+0x100/0x100 [ 339.383526] [<ffffffff9da638af>] newseg+0x49f/0xa70 [ 339.384371] [<ffffffff9dda0327>] ? debug_smp_processor_id+0x17/0x20 [ 339.385345] [<ffffffff9da63410>] ? shm_try_destroy_orphaned+0x190/0x190 [ 339.386365] [<ffffffff9da52cf0>] ? ipcget+0x60/0x510 [ 339.387139] [<ffffffff9da52d1f>] ipcget+0x8f/0x510 [ 339.387902] [<ffffffff9c0046f0>] ? do_audit_syscall_entry+0x2b0/0x2b0 [ 339.388931] [<ffffffff9da64e1a>] SyS_shmget+0x11a/0x160 [ 339.389737] [<ffffffff9da64d00>] ? is_file_shm_hugepages+0x40/0x40 [ 339.393268] [<ffffffff9c006ac2>] ? syscall_trace_enter_phase2+0x462/0x5f0 [ 339.395643] [<ffffffffa55ce0f8>] tracesys_phase2+0x88/0x8d Thanks, Sasha -- 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>