Re: [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece

From: "Huang\, Ying" <ying.huang@intel.com>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
	<linux-kernel@vger.kernel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Shaohua Li <shli@kernel.org>, Hugh Dickins <hughd@google.com>,
	Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Zi Yan <zi.yan@cs.rutgers.edu>
Subject: Re: [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece
Date: Thu, 25 Oct 2018 08:42:51 +0800	[thread overview]
Message-ID: <87ftwuvotw.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20181024172410.a3pibijoc2u2awwo@ca-dmjordan1.us.oracle.com> (Daniel Jordan's message of "Wed, 24 Oct 2018 10:24:10 -0700")

Daniel Jordan <daniel.m.jordan@oracle.com> writes:

> On Wed, Oct 24, 2018 at 11:31:42AM +0800, Huang, Ying wrote:
>> Hi, Daniel,
>> 
>> Daniel Jordan <daniel.m.jordan@oracle.com> writes:
>> 
>> > On Wed, Oct 10, 2018 at 03:19:03PM +0800, Huang Ying wrote:
>> >> And for all, Any comment is welcome!
>> >> 
>> >> This patchset is based on the 2018-10-3 head of mmotm/master.
>> >
>> > There seems to be some infrequent memory corruption with THPs that have been
>> > swapped out: page contents differ after swapin.
>> 
>> Thanks a lot for testing this!  I know there were big effort behind this
>> and it definitely will improve the quality of the patchset greatly!
>
> You're welcome!  Hopefully I'll have more results and tests to share in the
> next two weeks.
>
>> 
>> > Reproducer at the bottom.  Part of some tests I'm writing, had to separate it a
>> > little hack-ily.  Basically it writes the word offset _at_ each word offset in
>> > a memory blob, tries to push it to swap, and verifies the offset is the same
>> > after swapin.
>> >
>> > I ran with THP enabled=always.  THP swapin_enabled could be always or never, it
>> > happened with both.  Every time swapping occurred, a single THP-sized chunk in
>> > the middle of the blob had different offsets.  Example:
>> >
>> > ** > word corruption gap
>> > ** corruption detected 14929920 bytes in (got 15179776, expected 14929920) **
>> > ** corruption detected 14929928 bytes in (got 15179784, expected 14929928) **
>> > ** corruption detected 14929936 bytes in (got 15179792, expected 14929936) **
>> > ...pattern continues...
>> > ** corruption detected 17027048 bytes in (got 15179752, expected 17027048) **
>> > ** corruption detected 17027056 bytes in (got 15179760, expected 17027056) **
>> > ** corruption detected 17027064 bytes in (got 15179768, expected 17027064) **
>> 
>> 15179776 < 15179xxx <= 17027064
>> 
>> 15179776 % 4096 = 0
>> 
>> And 15179776 = 15179768 + 8
>> 
>> So I guess we have some alignment bug.  Could you try the patches
>> attached?  It deal with some alignment issue.
>
> That fixed it.  And removed three lines of code.  Nice :)

Thanks!  I will merge the fixes into the patchset.

Best Regards,
Huang, Ying