Hi guys, On 11/11/2012 02:01 PM, Rafael Aquini wrote: > Memory fragmentation introduced by ballooning might reduce significantly > the number of 2MB contiguous memory blocks that can be used within a guest, > thus imposing performance penalties associated with the reduced number of > transparent huge pages that could be used by the guest workload. > > This patch introduces the helper functions as well as the necessary changes > to teach compaction and migration bits how to cope with pages which are > part of a guest memory balloon, in order to make them movable by memory > compaction procedures. > > Signed-off-by: Rafael Aquini <aquini@xxxxxxxxxx> > Acked-by: Mel Gorman <mel@xxxxxxxxx> > --- I'm getting the following while fuzzing using trinity inside a KVM tools guest, on latest -next: [ 1642.783728] BUG: unable to handle kernel NULL pointer dereference at 0000000000000194 [ 1642.785083] IP: [<ffffffff8122b354>] isolate_migratepages_range+0x344/0x7b0 [ 1642.786061] PGD 39e80067 PUD 39f6d067 PMD 0 [ 1642.786766] Oops: 0000 [#3] PREEMPT SMP DEBUG_PAGEALLOC [ 1642.787587] CPU 0 [ 1642.787884] Pid: 8522, comm: trinity-child5 Tainted: G D W 3.7.0-rc5-next-20121115-sasha-00013-g37271d3 #154 [ 1642.789483] RIP: 0010:[<ffffffff8122b354>] [<ffffffff8122b354>] isolate_migratepages_range+0x344/0x7b0 [ 1642.790016] RSP: 0018:ffff880039d998d8 EFLAGS: 00010202 [ 1642.790016] RAX: 0000000000000054 RBX: ffffea0000fd5480 RCX: 00000000000001fa [ 1642.790016] RDX: 0000000080490049 RSI: 0000000000000004 RDI: ffff880039d99a20 [ 1642.790016] RBP: ffff880039d99978 R08: 0000000000000001 R09: 0000000000000000 [ 1642.790016] R10: ffff88003bfcefc0 R11: 0000000000000001 R12: 000000000003f552 [ 1642.790016] R13: 0000000000000153 R14: 0000000000000000 R15: ffff88004ffd2000 [ 1642.790016] FS: 00007ff799de5700(0000) GS:ffff880013600000(0000) knlGS:0000000000000000 [ 1642.790016] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1642.790016] CR2: 0000000000000194 CR3: 00000000369ef000 CR4: 00000000000406f0 [ 1642.790016] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1642.790016] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 1642.790016] Process trinity-child5 (pid: 8522, threadinfo ffff880039d98000, task ffff8800298e8000) [ 1642.790016] Stack: [ 1642.790016] 00000000000001fa ffff880039d99a78 ffff8800298e8000 ffff880039d99a30 [ 1642.790016] 0000000000000000 0000000000000000 0000000000000000 ffff880039d99fd8 [ 1642.790016] ffff880039d99a20 ffffea0000fd0000 ffff880039d99a60 000000000003f600 [ 1642.790016] Call Trace: [ 1642.790016] [<ffffffff8122ae10>] ? isolate_freepages+0x1f0/0x1f0 [ 1642.790016] [<ffffffff8122bc3e>] compact_zone+0x3ce/0x490 [ 1642.790016] [<ffffffff81185afb>] ? __lock_acquired+0x3b/0x360 [ 1642.790016] [<ffffffff8122bfee>] compact_zone_order+0xde/0x120 [ 1642.790016] [<ffffffff819f4bb8>] ? do_raw_spin_unlock+0xc8/0xe0 [ 1642.790016] [<ffffffff8122c0ee>] try_to_compact_pages+0xbe/0x110 [ 1642.790016] [<ffffffff83b53b4d>] __alloc_pages_direct_compact+0xba/0x206 [ 1642.790016] [<ffffffff8118f059>] ? on_each_cpu_mask+0xd9/0x110 [ 1642.790016] [<ffffffff8120e3ef>] __alloc_pages_nodemask+0x92f/0xbc0 [ 1642.790016] [<ffffffff8125284c>] alloc_pages_vma+0xfc/0x150 [ 1642.790016] [<ffffffff812699c1>] do_huge_pmd_anonymous_page+0x191/0x2b0 [ 1642.790016] [<ffffffff81137394>] ? __rcu_read_unlock+0x44/0xb0 [ 1642.790016] [<ffffffff812339f9>] handle_mm_fault+0x1c9/0x350 [ 1642.790016] [<ffffffff81234068>] __get_user_pages+0x418/0x5f0 [ 1642.790016] [<ffffffff81235bdc>] ? do_mlock_pages+0x8c/0x160 [ 1642.790016] [<ffffffff81235b43>] __mlock_vma_pages_range+0xb3/0xc0 [ 1642.790016] [<ffffffff81235c39>] do_mlock_pages+0xe9/0x160 [ 1642.790016] [<ffffffff812366e0>] sys_mlockall+0x160/0x1a0 [ 1642.790016] [<ffffffff83c1abd8>] tracesys+0xe1/0xe6 [ 1642.790016] Code: a9 00 00 01 00 0f 85 6c 02 00 00 48 8b 43 08 a8 01 0f 85 60 02 00 00 8b 53 18 85 d2 0f 89 55 02 00 00 48 85 c0 0f 84 4c 02 00 00 <48> 8b 80 40 01 00 00 a9 00 00 00 20 0f 84 3a 02 00 00 45 84 f6 [ 1642.790016] RIP [<ffffffff8122b354>] isolate_migratepages_range+0x344/0x7b0 [ 1642.790016] RSP <ffff880039d998d8> [ 1642.790016] CR2: 0000000000000194 [ 1643.398013] ---[ end trace 0ad6459aa62f5d72 ]--- My guess is that we see those because of a race during the check in isolate_migratepages_range(). 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>