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Date: Wed, 28 Mar 2018 17:26:20 +0800
From: Wei Yang <richard.weiyang@...il.com>
To: Jia He <hejianet@...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 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
>+ if (*last_idx != -1) {
>+ start_pfn = PFN_DOWN(type->regions[*last_idx].base);
To me, it should be PFN_UP().
>+ 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.
>+ 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
--
Wei Yang
Help you, Help me
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