linux-kernel - Re: [PATCH v2 00/12] THP support for ARC

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Date:	Fri, 9 Oct 2015 14:43:36 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	Minchan Kim <minchan@...nel.org>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 00/12] THP support for ARC

On Fri, Oct 09, 2015 at 04:59:43PM +0530, Vineet Gupta wrote:
> On Friday 09 October 2015 03:40 PM, Kirill A. Shutemov wrote:
> > On Fri, Oct 09, 2015 at 03:03:26PM +0530, Vineet Gupta wrote:
> >> On Thursday 01 October 2015 11:32 AM, Vineet Gupta wrote:
> >>> On Tuesday 22 September 2015 04:04 PM, Vineet Gupta wrote:
> >>>>> Hi,
> >>>>>
> >>>>> This series brings THP support to ARC. It also introduces an optional new
> >>>>> thp hook for arches to possibly optimize the TLB flush in thp regime.
> >>>>>
> >>>>> Please review !
> >>>>>
> >>>>> Changes Since v1 [*]
> >>>>>    - Rebased against v4.3-rc2
> >>>>>    - Switched ARC pgtable_t to pte_t * 		(Kiril)
> >>>>>    - Removed stub implementations for		(Andrew)
> >>>>> 	pmdp_set_access_flags, pmdp_test_and_clear_young, pmdp_set_wrprotect,
> >>>>> 	pmdp_collapse_flush, pmd_same
> >>>>>
> >>>>> [*] http://lkml.kernel.org/r/1440666194-21478-1-git-send-email-vgupta@synopsys.com
> >>>>>
> >>>>> Vineet Gupta (12):
> >>>>>   ARC: mm: switch pgtable_to to pte_t *
> >>>>>   ARC: mm: pte flags comsetic cleanups, comments
> >>>>>   ARC: mm: Introduce PTE_SPECIAL
> >>>>>   Documentation/features/vm: pte_special now supported by ARC
> >>>>>   ARCv2: mm: THP support
> >>>>>   ARCv2: mm: THP: boot validation/reporting
> >>>>>   Documentation/features/vm: THP now supported by ARC
> >>>>>   mm: move some code around
> >>>>>   mm,thp: reduce ifdef'ery for THP in generic code
> >>>>>   mm,thp: introduce flush_pmd_tlb_range
> >>>>>   ARCv2: mm: THP: Implement flush_pmd_tlb_range() optimization
> >>>>>   ARCv2: Add a DT which enables THP
> >>>>>
> >>>>>  Documentation/features/vm/THP/arch-support.txt     |  2 +-
> >>>>>  .../features/vm/pte_special/arch-support.txt       |  2 +-
> >>>>>  arch/arc/Kconfig                                   |  4 +
> >>>>>  arch/arc/boot/dts/hs_thp.dts                       | 59 +++++++++++++
> >>>>>  arch/arc/include/asm/hugepage.h                    | 82 ++++++++++++++++++
> >>>>>  arch/arc/include/asm/page.h                        |  5 +-
> >>>>>  arch/arc/include/asm/pgalloc.h                     |  6 +-
> >>>>>  arch/arc/include/asm/pgtable.h                     | 60 +++++++------
> >>>>>  arch/arc/mm/tlb.c                                  | 76 ++++++++++++++++-
> >>>>>  arch/arc/mm/tlbex.S                                | 21 +++--
> >>>>>  include/asm-generic/pgtable.h                      | 49 ++++-------
> >>>>>  mm/huge_memory.c                                   |  2 +-
> >>>>>  mm/pgtable-generic.c                               | 99 ++++++++++------------
> >>>>>  13 files changed, 345 insertions(+), 122 deletions(-)
> >>>>>  create mode 100644 arch/arc/boot/dts/hs_thp.dts
> >>>>>  create mode 100644 arch/arc/include/asm/hugepage.h
> >>> Andrew, Kirill, could you please review/ack the generic mm bits atleast so I can
> >>> proceed with moving the stuff into linux-next !
> >>
> >> Ping 2 !
> > 
> > Sorry.
> > 
> >> Can I please get some acks on the generic mm bits. Some of the changes
> >> will likely collide Kirill's THP rework !
> > 
> > Could you check if it acctually collides?
> 
> I rebased my changes on top of your v12 branch. As expected I get two merge
> conflicts as my patches update code which u have removed. But looks straight
> forward to resolve. Meaning we can carry respective patches and give Linus a heads
> up abt the merge conflict.
> 
> There's also a fixup needed for ARC to remove the pmdp splitting assuming ARC THP
> makes it into mainline first.

Okay. Let's see what hits upstream first.

Side question: I was surprised by your patchset. I didn't think about ARC
as an architecture which would benefit from THP. How big ARC systems
nowadays? How big benefit did you measured there from THP? 

-- 
 Kirill A. Shutemov
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