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Date: Thu, 29 Mar 2018 16:06:38 +0800
From: Jia He <hejianet@...il.com>
To: Wei Yang <richard.weiyang@...il.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>,
Daniel Vacek <neelx@...hat.com>,
Eugeniu Rosca <erosca@...adit-jv.com>,
Vlastimil Babka <vbabka@...e.cz>, 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 2/5] mm: page_alloc: reduce unnecessary binary search
in memblock_next_valid_pfn()
On 3/28/2018 5:26 PM, Wei Yang Wrote:
> On Sun, Mar 25, 2018 at 08:02:16PM -0700, Jia He 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. if pfn and pfn+1 are in the same
>> memblock region, we can simply pfn++ instead of doing the binary search
>> in memblock_next_valid_pfn. This patch only works when
>> CONFIG_HAVE_ARCH_PFN_VALID is enable.
>>
>> Signed-off-by: Jia He <jia.he@...-semitech.com>
>> ---
>> include/linux/memblock.h | 2 +-
>> mm/memblock.c | 73 +++++++++++++++++++++++++++++-------------------
>> mm/page_alloc.c | 3 +-
>> 3 files changed, 47 insertions(+), 31 deletions(-)
>>
>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> index efbbe4b..a8fb2ab 100644
>> --- a/include/linux/memblock.h
>> +++ b/include/linux/memblock.h
>> @@ -204,7 +204,7 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
>> #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>>
>> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> -unsigned long memblock_next_valid_pfn(unsigned long pfn);
>> +unsigned long memblock_next_valid_pfn(unsigned long pfn, int *idx);
>> #endif
>>
>> /**
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index bea5a9c..06c1a08 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -1102,35 +1102,6 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
>> *out_nid = r->nid;
>> }
>>
>> -#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> -unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
>> -{
>> - struct memblock_type *type = &memblock.memory;
>> - unsigned int right = type->cnt;
>> - unsigned int mid, left = 0;
>> - phys_addr_t addr = PFN_PHYS(++pfn);
>> -
>> - do {
>> - mid = (right + left) / 2;
>> -
>> - if (addr < type->regions[mid].base)
>> - right = mid;
>> - else if (addr >= (type->regions[mid].base +
>> - type->regions[mid].size))
>> - left = mid + 1;
>> - else {
>> - /* addr is within the region, so pfn is valid */
>> - return pfn;
>> - }
>> - } while (left < right);
>> -
>> - if (right == type->cnt)
>> - return -1UL;
>> - else
>> - return PHYS_PFN(type->regions[right].base);
>> -}
>> -#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>> -
>> /**
>> * memblock_set_node - set node ID on memblock regions
>> * @base: base of area to set node ID for
>> @@ -1162,6 +1133,50 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
>> }
>> #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>>
>> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
>> + int *last_idx)
>> +{
>> + struct memblock_type *type = &memblock.memory;
>> + unsigned int right = type->cnt;
>> + unsigned int mid, left = 0;
>> + unsigned long start_pfn, end_pfn;
>> + phys_addr_t addr = PFN_PHYS(++pfn);
>> +
>> + /* fast path, return pfh+1 if next pfn is in the same region */
> ^^^ pfn
Thanks
>> + if (*last_idx != -1) {
>> + start_pfn = PFN_DOWN(type->regions[*last_idx].base);
> To me, it should be PFN_UP().
hmm.., seems all the base of memory region is pfn aligned (0x10000
aligned). So
PFN_UP is the same as PFN_DOWN here?
I got this logic from memblock_search_pfn_nid()
Cheers,
Jia
>
>> + end_pfn = PFN_DOWN(type->regions[*last_idx].base +
>> + type->regions[*last_idx].size);
>> +
>> + if (pfn < end_pfn && pfn > start_pfn)
> Could be (pfn < end_pfn && pfn >= start_pfn)?
>
> pfn == start_pfn is also a valid address.
No, pfn=pfn+1 at the beginning, so pfn != start_pfn
>
>> + return pfn;
>> + }
>> +
>> + /* slow path, do the binary searching */
>> + do {
>> + mid = (right + left) / 2;
>> +
>> + if (addr < type->regions[mid].base)
>> + right = mid;
>> + else if (addr >= (type->regions[mid].base +
>> + type->regions[mid].size))
>> + left = mid + 1;
>> + else {
>> + *last_idx = mid;
>> + return pfn;
>> + }
>> + } while (left < right);
>> +
>> + if (right == type->cnt)
>> + return -1UL;
>> +
>> + *last_idx = right;
>> +
>> + return PHYS_PFN(type->regions[*last_idx].base);
>> +}
>> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
> The same comment as Daniel, you are moving the function out of
> CONFIG_HAVE_MEMBLOCK_NODE_MAP.
>> +
>> static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
>> phys_addr_t align, phys_addr_t start,
>> phys_addr_t end, int nid, ulong flags)
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 2a967f7..0bb0274 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5459,6 +5459,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>> unsigned long end_pfn = start_pfn + size;
>> pg_data_t *pgdat = NODE_DATA(nid);
>> unsigned long pfn;
>> + int idx = -1;
>> unsigned long nr_initialised = 0;
>> struct page *page;
>> #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
>> @@ -5490,7 +5491,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>> * end_pfn), such that we hit a valid pfn (or end_pfn)
>> * on our next iteration of the loop.
>> */
>> - pfn = memblock_next_valid_pfn(pfn) - 1;
>> + pfn = memblock_next_valid_pfn(pfn, &idx) - 1;
>> #endif
>> continue;
>> }
>> --
>> 2.7.4
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