Re: [PATCH v12 4/7] mm: introduce compaction and migration for ballooned pages

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 <redacted>
Acked-by: Mel Gorman <redacted>
---

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

On Sat, Nov 17, 2012 at 01:01:30PM -0500, Sasha Levin wrote:

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

My guess is that we see those because of a race during the check in
isolate_migratepages_range().


Thanks,
Sasha

Sasha, could you share your .config and steps you did used with trinity? So I
can attempt to reproduce this issue you reported.

Thanks, 
Rafael