linux-kernel - Re: [RESEND PATCH v10 3/6] mm: page_alloc: reduce unnecessary binary search in memblock_next_valid

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Date:   Tue, 21 Aug 2018 14:08:29 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Jia He <hejianet@...il.com>
Cc:     Pasha Tatashin <Pavel.Tatashin@...rosoft.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Michal Hocko <mhocko@...e.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Philip Derrin <philip@....systems>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        James Morse <james.morse@....com>,
        Steve Capper <steve.capper@....com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        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>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Daniel Vacek <neelx@...hat.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Jia He <jia.he@...-semitech.com>
Subject: Re: [RESEND PATCH v10 3/6] mm: page_alloc: reduce unnecessary
 binary search in memblock_next_valid_pfn()

On Tue, 21 Aug 2018 14:14:30 +0800 Jia He <hejianet@...il.com> wrote:

> Hi Pasha
> 
> On 8/17/2018 9:08 AM, Pasha Tatashin Wrote:
> > 
> >> Signed-off-by: Jia He <jia.he@...-semitech.com>
> >> ---
> >>  mm/memblock.c | 37 +++++++++++++++++++++++++++++--------
> >>  1 file changed, 29 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/mm/memblock.c b/mm/memblock.c
> >> index ccad225..84f7fa7 100644
> >> --- a/mm/memblock.c
> >> +++ b/mm/memblock.c
> >> @@ -1140,31 +1140,52 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
> >>  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
> >>  
> >>  #ifdef CONFIG_HAVE_MEMBLOCK_PFN_VALID
> >> +static int early_region_idx __init_memblock = -1;
> > 
> > One comment:
> > 
> > This should be __initdata, but even better bring it inside the function
> > as local static variable.
> > 
> Seems it should be __initdata_memblock instead of __initdata?
> 

Eh, it's 4 bytes.

It should however be local to the sole function which uses it.

And what's this "ulong" thing?  mm/ uses unsigned long.

--- a/mm/memblock.c~mm-page_alloc-reduce-unnecessary-binary-search-in-memblock_next_valid_pfn-fix
+++ a/mm/memblock.c
@@ -1232,15 +1232,15 @@ int __init_memblock memblock_set_node(ph
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
 #ifdef CONFIG_HAVE_MEMBLOCK_PFN_VALID
-static int early_region_idx __init_memblock = -1;
-ulong __init_memblock memblock_next_valid_pfn(ulong pfn)
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
 {
 	struct memblock_type *type = &memblock.memory;
 	struct memblock_region *regions = type->regions;
 	uint right = type->cnt;
 	uint mid, left = 0;
-	ulong start_pfn, end_pfn, next_start_pfn;
+	unsigned long start_pfn, end_pfn, next_start_pfn;
 	phys_addr_t addr = PFN_PHYS(++pfn);
+	static int early_region_idx __initdata_memblock = -1;
 
 	/* fast path, return pfn+1 if next pfn is in the same region */
 	if (early_region_idx != -1) {
--- a/include/linux/mmzone.h~mm-page_alloc-reduce-unnecessary-binary-search-in-memblock_next_valid_pfn-fix
+++ a/include/linux/mmzone.h
@@ -1269,7 +1269,7 @@ static inline int pfn_present(unsigned l
 
 #define early_pfn_valid(pfn)	pfn_valid(pfn)
 #ifdef CONFIG_HAVE_MEMBLOCK_PFN_VALID
-extern ulong memblock_next_valid_pfn(ulong pfn);
+extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
 #define next_valid_pfn(pfn)	memblock_next_valid_pfn(pfn)
 #endif
 void sparse_init(void);
_