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From: "Luck, Tony" <tony.luck@intel.com>
To: Jane Chu <jane.chu@oracle.com>, Matthew Wilcox <willy@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>,
	Naoya Horiguchi <naoya.horiguchi@nec.com>,
	"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	David Rientjes <rientjes@google.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	Peter Xu <peterx@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>
Subject: RE: [RFC] Make the memory failure blast radius more precise
Date: Thu, 25 Jun 2020 00:13:43 +0000
Message-ID: <3908561D78D1C84285E8C5FCA982C28F7F67BB29@ORSMSX115.amr.corp.intel.com> (raw)
In-Reply-To: <24367ca1-ecb0-de96-b9e5-f94747838c74@oracle.com>

> Both the RFC patch and the above 5-step recovery plan look neat, step 4) 
> is nice to carry forward on icelake when a single instruction to clear
> poison is available.

Jane,

Clearing poison has some challenges.

On persistent memory it probably works (as the DIMM is going to remap that address to a different
part of the media to avoid the bad spot).

On DDR memory you'd need to decide whether the problem was transient, so that a simple
overwrite fixes the problem. Or persistent ... in which case the problem will likely come back
with the right data pattern.  To tell that you may need to run some memory test on the affected
area.

If the error was just in a 4K page, I'd be inclined to copy the good data to a new page and
map that in instead. Throwing away one 4K page isn't likely to be painful.

If it is in a 2M/1G page ... perhaps it is worth the effort and risk of trying to clear the poison
in place to avoid the pain of breaking up a large page.

-Tony

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 20:17 Matthew Wilcox
2020-06-23 21:48 ` Dan Williams
2020-06-23 22:04 ` Luck, Tony
2020-06-23 22:17   ` Matthew Wilcox
2020-06-23 22:26     ` Luck, Tony
2020-06-23 22:40       ` Matthew Wilcox
2020-06-24  0:01         ` Darrick J. Wong
2020-06-24 12:10           ` Matthew Wilcox
2020-06-24 23:21             ` Dan Williams
2020-06-25  0:17               ` Matthew Wilcox
2020-06-25  1:18                 ` Dan Williams
2020-06-24 21:22         ` Jane Chu
2020-06-25  0:13           ` Luck, Tony [this message]
2020-06-25 16:23             ` Jane Chu
2020-06-24  4:32   ` David Rientjes
2020-06-24 20:57     ` Jane Chu
2020-06-24 22:01       ` David Rientjes
2020-06-25  2:16     ` HORIGUCHI NAOYA(堀口 直也)

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