linux-kernel - Re: [PATCH v3 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn

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Message-ID: <55b15841-bac7-7576-6da8-edff0fe0e9b2@gmail.com>
Date:   Wed, 28 Mar 2018 10:10:25 +0800
From:   Jia He <hejianet@...il.com>
To:     Daniel Vacek <neelx@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mel Gorman <mgorman@...e.de>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Steven Sistare <steven.sistare@...cle.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        open list <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        James Morse <james.morse@....com>,
        Steve Capper <steve.capper@....com>, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Kemi Wang <kemi.wang@...el.com>,
        Petr Tesarik <ptesarik@...e.com>,
        YASUAKI ISHIMATSU <yasu.isimatu@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Jia He <jia.he@...-semitech.com>
Subject: Re: [PATCH v3 5/5] mm: page_alloc: reduce unnecessary binary search
 in early_pfn_valid()



On 3/28/2018 1:51 AM, Daniel Vacek Wrote:
> On Mon, Mar 26, 2018 at 5:02 AM, Jia He <hejianet@...il.com> wrote:
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") optimized the loop in memmap_init_zone(). But there is
>> still some room for improvement. E.g. in early_pfn_valid(), if pfn and
>> pfn+1 are in the same memblock region, we can record the last returned
>> memblock region index and check check pfn++ is still in the same region.
>>
>> Currently it only improve the performance on arm64 and will have no
>> impact on other arches.
>>
>> Signed-off-by: Jia He <jia.he@...-semitech.com>
>> ---
>>   arch/x86/include/asm/mmzone_32.h |  2 +-
>>   include/linux/mmzone.h           | 12 +++++++++---
>>   mm/page_alloc.c                  |  2 +-
>>   3 files changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
>> index 73d8dd1..329d3ba 100644
>> --- a/arch/x86/include/asm/mmzone_32.h
>> +++ b/arch/x86/include/asm/mmzone_32.h
>> @@ -49,7 +49,7 @@ static inline int pfn_valid(int pfn)
>>          return 0;
>>   }
>>
>> -#define early_pfn_valid(pfn)   pfn_valid((pfn))
>> +#define early_pfn_valid(pfn, last_region_idx)  pfn_valid((pfn))
>>
>>   #endif /* CONFIG_DISCONTIGMEM */
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index d797716..3a686af 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -1267,9 +1267,15 @@ static inline int pfn_present(unsigned long pfn)
>>   })
>>   #else
>>   #define pfn_to_nid(pfn)                (0)
>> -#endif
>> +#endif /*CONFIG_NUMA*/
>> +
>> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +#define early_pfn_valid(pfn, last_region_idx) \
>> +                               pfn_valid_region(pfn, last_region_idx)
>> +#else
>> +#define early_pfn_valid(pfn, last_region_idx)  pfn_valid(pfn)
>> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>>
>> -#define early_pfn_valid(pfn)   pfn_valid(pfn)
>>   void sparse_init(void);
>>   #else
>>   #define sparse_init()  do {} while (0)
>> @@ -1288,7 +1294,7 @@ struct mminit_pfnnid_cache {
>>   };
>>
>>   #ifndef early_pfn_valid
>> -#define early_pfn_valid(pfn)   (1)
>> +#define early_pfn_valid(pfn, last_region_idx)  (1)
>>   #endif
>>
>>   void memory_present(int nid, unsigned long start, unsigned long end);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 0bb0274..debccf3 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5484,7 +5484,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>                  if (context != MEMMAP_EARLY)
>>                          goto not_early;
>>
>> -               if (!early_pfn_valid(pfn)) {
>> +               if (!early_pfn_valid(pfn, &idx)) {
>>   #if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID)
>>                          /*
>>                           * Skip to the pfn preceding the next valid one (or
>> --
>> 2.7.4
>>
> Hmm, what about making index global variable instead of changing all
> the prototypes? Similar to early_pfnnid_cache for example. Something
> like:
>
> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
> extern int early_region_idx __meminitdata;
> #define early_pfn_valid(pfn) \
>                                 pfn_valid_region(pfn, &early_region_idx)
> #else
> #define early_pfn_valid(pfn)  pfn_valid(pfn)
> #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>
> And move this to arch/arm64/include/asm/page.h ?
>
> --nX
>
Yes. ok with me

-- 
Cheers,
Jia