From: Madhavan Srinivasan <maddy@linux•vnet.ibm.com>
To: "Kirill A. Shutemov" <kirill@shutemov•name>
Cc: linux-arch@vger•kernel.org, riel@redhat•com,
rusty@rustcorp•com.au, peterz@infradead•org, x86@kernel•org,
linux-kernel@vger•kernel.org, linux-mm@kvack•org,
ak@linux•intel.com, paulus@samba•org, mgorman@suse•de,
akpm@linux-foundation•org, linuxppc-dev@lists•ozlabs.org,
mingo@kernel•org, kirill.shutemov@linux•intel.com
Subject: Re: [PATCH 1/1] mm: move FAULT_AROUND_ORDER to arch/
Date: Thu, 27 Mar 2014 11:50:05 +0530 [thread overview]
Message-ID: <5333C315.3000405@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140325173605.GA21411@node.dhcp.inet.fi>
On Tuesday 25 March 2014 11:06 PM, Kirill A. Shutemov wrote:
> On Tue, Mar 25, 2014 at 12:20:15PM +0530, Madhavan Srinivasan wrote:
>> Kirill A. Shutemov with the commit 96bacfe542 introduced
>> vm_ops->map_pages() for mapping easy accessible pages around
>> fault address in hope to reduce number of minor page faults.
>> Based on his workload runs, suggested FAULT_AROUND_ORDER
>> (knob to control the numbers of pages to map) is 4.
>>
>> This patch moves the FAULT_AROUND_ORDER macro to arch/ for
>> architecture maintainers to decide on suitable FAULT_AROUND_ORDER
>> value based on performance data for that architecture.
>>
>> Signed-off-by: Madhavan Srinivasan <maddy@linux•vnet.ibm.com>
>> ---
>> arch/powerpc/include/asm/pgtable.h | 6 ++++++
>> arch/x86/include/asm/pgtable.h | 5 +++++
>> include/asm-generic/pgtable.h | 10 ++++++++++
>> mm/memory.c | 2 --
>> 4 files changed, 21 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
>> index 3ebb188..9fcbd48 100644
>> --- a/arch/powerpc/include/asm/pgtable.h
>> +++ b/arch/powerpc/include/asm/pgtable.h
>> @@ -19,6 +19,12 @@ struct mm_struct;
>> #endif
>>
>> /*
>> + * With a few real world workloads that were run,
>> + * the performance data showed that a value of 3 is more advantageous.
>> + */
>> +#define FAULT_AROUND_ORDER 3
>> +
>> +/*
>> * We save the slot number & secondary bit in the second half of the
>> * PTE page. We use the 8 bytes per each pte entry.
>> */
>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
>> index 938ef1d..8387a65 100644
>> --- a/arch/x86/include/asm/pgtable.h
>> +++ b/arch/x86/include/asm/pgtable.h
>> @@ -7,6 +7,11 @@
>> #include <asm/pgtable_types.h>
>>
>> /*
>> + * Based on Kirill's test results, fault around order is set to 4
>> + */
>> +#define FAULT_AROUND_ORDER 4
>> +
>> +/*
>> * Macro to mark a page protection value as UC-
>> */
>> #define pgprot_noncached(prot) \
>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>> index 1ec08c1..62f7f07 100644
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -7,6 +7,16 @@
>> #include <linux/mm_types.h>
>> #include <linux/bug.h>
>>
>> +
>> +/*
>> + * Fault around order is a control knob to decide the fault around pages.
>> + * Default value is set to 0UL (disabled), but the arch can override it as
>> + * desired.
>> + */
>> +#ifndef FAULT_AROUND_ORDER
>> +#define FAULT_AROUND_ORDER 0UL
>> +#endif
>
> FAULT_AROUND_ORDER == 0 case should be handled separately in
> do_read_fault(): no reason to go to do_fault_around() if we are going to
> fault in only one page.
>
ok agreed. I am thinking of adding FAULT_AROUND_ORDER check with
map_pages check in the do_read_fault. Kindly share your thoughts.
With regards
Maddy
next prev parent reply other threads:[~2014-03-27 6:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-25 6:50 [PATCH 0/1] mm: FAULT_AROUND_ORDER patchset performance data for powerpc Madhavan Srinivasan
2014-03-25 6:50 ` [PATCH 1/1] mm: move FAULT_AROUND_ORDER to arch/ Madhavan Srinivasan
2014-03-25 17:36 ` Kirill A. Shutemov
2014-03-25 17:50 ` Dave Hansen
2014-04-02 4:45 ` Madhavan Srinivasan
2014-03-27 6:20 ` Madhavan Srinivasan [this message]
2014-03-25 8:11 ` [PATCH 0/1] mm: FAULT_AROUND_ORDER patchset performance data for powerpc Ingo Molnar
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