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From: Aristeu Rozanski <>
To: Oscar Salvador <>,
Subject: Re: [PATCH v3 0/5] HWpoison: further fixes and cleanups
Date: Tue, 15 Sep 2020 17:22:22 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Oscar, Naoya,

On Mon, Sep 14, 2020 at 12:15:54PM +0200, Oscar Salvador wrote:
> The important bit of this patchset is patch#1, which is a fix to take off
> HWPoison pages off a buddy freelist since it can lead us to having HWPoison
> pages back in the game without no one noticing it.
> So fix it (we did that already for soft_offline_page [1]).
> The other patches are clean-ups and not that important, so if anything,
> consider patch#1 for inclusion.
> [1]

I found something strange with your and Naoya's hwpoison rework. We have a
customer with a testcase that basically does:


	madvise(p1, size, MADV_MERGEABLE);
	madvise(p2, size, MADV_MERGEABLE);

	memset(p1, 'a', size);
	memset(p2, 'a', size);

	madvise(p1, size, MADV_SOFT_OFFLINE);

	madvise(p1, size, MADV_UNMERGEABLE);
	madvise(p2, size, MADV_UNMERGEABLE);

where size is about 200,000 pages. It works on a x86_64 box (with and without the
hwpoison rework). On ppc64 boxes (tested 3 different ones with at least 250GB memory)
it fails to take a page off the buddy list (page_handle_poison()/take_page_off_buddy())
(madvise MADV_SOFT_OFFLINE returns -EBUSY). Without the hwpoison rework the test passes.

Possibly related is that ppc64 takes a long time to run this test and according
perf, it spends most of the time clearing pages:

	  17.15%  ksm_poison  [kernel.kallsyms]  [k] copypage_power7
	  13.39%  ksm_poison  [kernel.kallsyms]  [k] clear_user_page
	   8.70%  ksm_poison       [.] __memset_power8
	   8.63%  ksm_poison  [kernel.kallsyms]  [k] opal_return
	   6.04%  ksm_poison  [kernel.kallsyms]  [k] __opal_call
	   2.67%  ksm_poison  [kernel.kallsyms]  [k] opal_call
	   1.52%  ksm_poison  [kernel.kallsyms]  [k] _raw_spin_lock
	   1.45%  ksm_poison  [kernel.kallsyms]  [k] opal_flush_console
	   1.43%  ksm_poison  [unknown]          [k] 0x0000000030005138
	   1.43%  ksm_poison  [kernel.kallsyms]  [k] opal_console_write_buffer_space
	   1.26%  ksm_poison  [kernel.kallsyms]  [k] hvc_console_print

I've run these tests using mmotm and mmotm with this patchset on top.

Do you know what might be happening here?


  parent reply	other threads:[~2020-09-15 22:01 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 10:15 [PATCH v3 0/5] HWpoison: further fixes and cleanups Oscar Salvador
2020-09-14 10:15 ` [PATCH v3 1/5] mm,hwpoison: take free pages off the buddy freelists Oscar Salvador
2020-09-14 10:15 ` [PATCH v3 2/5] mm,hwpoison: refactor madvise_inject_error Oscar Salvador
2020-09-14 10:15 ` [PATCH v3 3/5] mm,hwpoison: drain pcplists before bailing out for non-buddy zero-refcount page Oscar Salvador
2020-09-14 10:15 ` [PATCH v3 4/5] mm,hwpoison: drop unneeded pcplist draining Oscar Salvador
2020-09-14 10:15 ` [PATCH v3 5/5] mm,hwpoison: remove stale code Oscar Salvador
2020-09-15 21:22 ` Aristeu Rozanski [this message]
2020-09-16  7:27   ` [PATCH v3 0/5] HWpoison: further fixes and cleanups Oscar Salvador
2020-09-16 13:53     ` Aristeu Rozanski
2020-09-16 14:09       ` Oscar Salvador
2020-09-16 14:46         ` Aristeu Rozanski
2020-09-16 16:30           ` osalvador
2020-09-16 16:34             ` osalvador
2020-09-16 17:58               ` Aristeu Rozanski
2020-09-16 18:12                 ` osalvador
2020-09-16 13:42   ` HORIGUCHI NAOYA(堀口 直也)
2020-09-16 14:06     ` Oscar Salvador

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