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Message-ID: <1360205438.13550.11.camel@ThinkPad-T5421.cn.ibm.com> Date: Thu, 07 Feb 2013 10:50:38 +0800 From: Li Zhong <zhong@...ux.vnet.ibm.com> To: Sasha Levin <sasha.levin@...cle.com> Cc: Michel Lespinasse <walken@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 3/3] mm: accelerate munlock() treatment of THP pages On Wed, 2013-02-06 at 18:44 -0500, Sasha Levin wrote: > On 02/04/2013 02:17 AM, Michel Lespinasse wrote: > > munlock_vma_pages_range() was always incrementing addresses by PAGE_SIZE > > at a time. When munlocking THP pages (or the huge zero page), this resulted > > in taking the mm->page_table_lock 512 times in a row. > > > > We can do better by making use of the page_mask returned by follow_page_mask > > (for the huge zero page case), or the size of the page munlock_vma_page() > > operated on (for the true THP page case). > > > > Note - I am sending this as RFC only for now as I can't currently put > > my finger on what if anything prevents split_huge_page() from operating > > concurrently on the same page as munlock_vma_page(), which would mess > > up our NR_MLOCK statistics. Is this a latent bug or is there a subtle > > point I missed here ? > > > > Signed-off-by: Michel Lespinasse <walken@...gle.com> > > Hi Michel, > > Fuzzing with trinity inside a KVM tools guest produces a steady stream of: > > > [ 51.823275] ------------[ cut here ]------------ > [ 51.823302] kernel BUG at include/linux/page-flags.h:421! > [ 51.823307] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > [ 51.823307] Dumping ftrace buffer: > [ 51.823314] (ftrace buffer empty) > [ 51.823314] Modules linked in: > [ 51.823314] CPU 2 > [ 51.823314] Pid: 7116, comm: trinity Tainted: G W 3.8.0-rc6-next-20130206-sasha-00027-g3b5963c-dirty #273 > [ 51.823316] RIP: 0010:[<ffffffff81242792>] [<ffffffff81242792>] munlock_vma_page+0x12/0xf0 > [ 51.823317] RSP: 0018:ffff880009641bb8 EFLAGS: 00010282 > [ 51.823319] RAX: 011ffc0000008001 RBX: ffffea0000410040 RCX: 0000000000000000 > [ 51.823320] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0000410040 > [ 51.823321] RBP: ffff880009641bc8 R08: 0000000000000000 R09: 0000000000000000 > [ 51.823322] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880009633958 > [ 51.823324] R13: 0000000001252000 R14: ffffea0000410040 R15: 00000000000000ff > [ 51.823326] FS: 00007fe7a9046700(0000) GS:ffff88000ba00000(0000) knlGS:0000000000000000 > [ 51.823327] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 51.823328] CR2: 00007fc583b90fcb CR3: 0000000009bc8000 CR4: 00000000000406e0 > [ 51.823334] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 51.823338] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > [ 51.823340] Process trinity (pid: 7116, threadinfo ffff880009640000, task ffff880009638000) > [ 51.823341] Stack: > [ 51.823344] 0000000000a01000 ffff880009633958 ffff880009641c08 ffffffff812429bd > [ 51.823373] ffff880009638000 000001ff09638000 ffff880009ade000 ffff880009633958 > [ 51.823373] ffff880009638810 ffff880009ade098 ffff880009641cb8 ffffffff81246d81 > [ 51.823373] Call Trace: > [ 51.823373] [<ffffffff812429bd>] munlock_vma_pages_range+0x8d/0xf0 > [ 51.823373] [<ffffffff81246d81>] exit_mmap+0x51/0x170 > [ 51.823373] [<ffffffff81278b4a>] ? __khugepaged_exit+0x8a/0xf0 > [ 51.823373] [<ffffffff8126a09f>] ? kmem_cache_free+0x22f/0x3b0 > [ 51.823373] [<ffffffff81278b4a>] ? __khugepaged_exit+0x8a/0xf0 > [ 51.823373] [<ffffffff8110af97>] mmput+0x77/0xe0 > [ 51.823377] [<ffffffff81114403>] exit_mm+0x113/0x120 > [ 51.823381] [<ffffffff83d727f1>] ? _raw_spin_unlock_irq+0x51/0x80 > [ 51.823384] [<ffffffff8111465a>] do_exit+0x24a/0x590 > [ 51.823387] [<ffffffff81114a6a>] do_group_exit+0x8a/0xc0 > [ 51.823390] [<ffffffff81128591>] get_signal_to_deliver+0x501/0x5b0 > [ 51.823394] [<ffffffff8106dd42>] do_signal+0x42/0x110 > [ 51.823399] [<ffffffff811d8ea4>] ? rcu_eqs_exit_common+0x64/0x340 > [ 51.823404] [<ffffffff81184a0d>] ? trace_hardirqs_on+0xd/0x10 > [ 51.823407] [<ffffffff811849c8>] ? trace_hardirqs_on_caller+0x128/0x160 > [ 51.823409] [<ffffffff81184a0d>] ? trace_hardirqs_on+0xd/0x10 > [ 51.823412] [<ffffffff8106de58>] do_notify_resume+0x48/0xa0 > [ 51.823415] [<ffffffff83d732fb>] retint_signal+0x4d/0x92 > [ 51.823449] Code: 85 c0 75 0d 48 89 df e8 0d 30 fe ff 0f 1f 44 00 00 48 83 c4 08 5b 5d c3 90 55 48 89 e5 41 54 53 48 89 fb 48 > 8b 07 f6 c4 80 74 06 <0f> 0b 0f 1f 40 00 48 8b 07 48 c1 e8 0e 83 e0 01 83 f8 01 48 8b > [ 51.823449] RIP [<ffffffff81242792>] munlock_vma_page+0x12/0xf0 > [ 51.823450] RSP <ffff880009641bb8> > [ 51.826846] ---[ end trace a7919e7f17c0a72a ]--- > The similar warning prevents my system from booting. And it seems to me that in munlock_vma_pages_range(), the page_mask needs be the page number returned from munlock_vma_page() minus 1. And the following fix solved my problem. Would you please have a try? Thanks, Zhong ================ diff --git a/mm/mlock.c b/mm/mlock.c index af1d115..1e3d794 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -255,7 +255,7 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, unlock_page(page); put_page(page); } - page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); + page_increm = 1 + (~(start >> PAGE_SHIFT) & (page_mask-1)); start += page_increm * PAGE_SIZE; cond_resched(); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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