[PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Aneesh Kumar K.V]

For ppc64, we want to call this function when we are not running as guest.
Also, if we failed to allocate hugepages, let the user know.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 include/linux/hugetlb.h | 1 +
 mm/hugetlb.c            | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0ed8e41aaf11..8bbbd37ab105 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -358,6 +358,7 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
 			pgoff_t idx);
 
 /* arch callback */
+int __init __alloc_bootmem_huge_page(struct hstate *h);
 int __init alloc_bootmem_huge_page(struct hstate *h);
 
 void __init hugetlb_bad_size(void);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bc48ee783dd9..a3a7a7e6339e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
 	return page;
 }
 
-int __weak alloc_bootmem_huge_page(struct hstate *h)
+int alloc_bootmem_huge_page(struct hstate *h)
+	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
+int __alloc_bootmem_huge_page(struct hstate *h)
 {
 	struct huge_bootmem_page *m;
 	int nr_nodes, node;
@@ -2104,6 +2106,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
 			goto found;
 		}
 	}
+	pr_info("Failed to allocate hugepage of size %ld\n", huge_page_size(h));
 	return 0;
 
 found:
-- 
2.13.3

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[PATCH v3 2/3] powerpc/mm/hugetlb: Add support for reserving gigantic huge pages via kernel command line

[Aneesh Kumar K.V]

With commit aa888a74977a8 ("hugetlb: support larger than MAX_ORDER") we added
support for allocating gigantic hugepages via kernel command line. Switch
ppc64 arch specific code to use that.

W.r.t FSL support, we now limit our allocation range using BOOTMEM_ALLOC_ACCESSIBLE.

We use the kernel command line to do reservation of hugetlb pages on powernv
platforms. On pseries hash mmu mode the supported gigantic huge page size is
16GB and that can only be allocated with hypervisor assist. For pseries the
command line option doesn't do the allocation. Instead pseries does gigantic
hugepage allocation based on hypervisor hint that is specified via
"ibm,expected#pages" property of the memory node.

Cc: Scott Wood <oss@buserror.net>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/mmu-hash.h |   2 +-
 arch/powerpc/include/asm/hugetlb.h            |  14 --
 arch/powerpc/kernel/setup-common.c            |   7 -
 arch/powerpc/mm/hash_utils_64.c               |   2 +-
 arch/powerpc/mm/hugetlbpage.c                 | 177 +++-----------------------
 arch/powerpc/mm/init_32.c                     |   2 -
 6 files changed, 22 insertions(+), 182 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
index 6981a52b3887..f28d21c69f79 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
@@ -468,7 +468,7 @@ extern int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
 			     int psize, int ssize);
 int htab_remove_mapping(unsigned long vstart, unsigned long vend,
 			int psize, int ssize);
-extern void add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages);
+extern void pseries_add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages);
 extern void demote_segment_4k(struct mm_struct *mm, unsigned long addr);
 
 #ifdef CONFIG_PPC_PSERIES
diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
index 7f4025a6c69e..b8a0fb442c64 100644
--- a/arch/powerpc/include/asm/hugetlb.h
+++ b/arch/powerpc/include/asm/hugetlb.h
@@ -218,18 +218,4 @@ static inline pte_t *hugepte_offset(hugepd_t hpd, unsigned long addr,
 }
 #endif /* CONFIG_HUGETLB_PAGE */
 
-/*
- * FSL Book3E platforms require special gpage handling - the gpages
- * are reserved early in the boot process by memblock instead of via
- * the .dts as on IBM platforms.
- */
-#if defined(CONFIG_HUGETLB_PAGE) && (defined(CONFIG_PPC_FSL_BOOK3E) || \
-    defined(CONFIG_PPC_8xx))
-extern void __init reserve_hugetlb_gpages(void);
-#else
-static inline void reserve_hugetlb_gpages(void)
-{
-}
-#endif
-
 #endif /* _ASM_POWERPC_HUGETLB_H */
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 94a948207cd2..0f896f17d5ab 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -916,13 +916,6 @@ void __init setup_arch(char **cmdline_p)
 	/* Reserve large chunks of memory for use by CMA for KVM. */
 	kvm_cma_reserve();
 
-	/*
-	 * Reserve any gigantic pages requested on the command line.
-	 * memblock needs to have been initialized by the time this is
-	 * called since this will reserve memory.
-	 */
-	reserve_hugetlb_gpages();
-
 	klp_init_thread_info(&init_thread_info);
 
 	init_mm.start_code = (unsigned long)_stext;
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 7a20669c19e7..2f1f6bc04012 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -509,7 +509,7 @@ static int __init htab_dt_scan_hugepage_blocks(unsigned long node,
 			phys_addr, block_size, expected_pages);
 	if (phys_addr + (16 * GB) <= memblock_end_of_DRAM()) {
 		memblock_reserve(phys_addr, block_size * expected_pages);
-		add_gpage(phys_addr, block_size, expected_pages);
+		pseries_add_gpage(phys_addr, block_size, expected_pages);
 	}
 	return 0;
 }
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index e1bf5ca397fe..a0271d738a30 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -36,26 +36,6 @@
 unsigned int HPAGE_SHIFT;
 EXPORT_SYMBOL(HPAGE_SHIFT);
 
-/*
- * Tracks gpages after the device tree is scanned and before the
- * huge_boot_pages list is ready.  On non-Freescale implementations, this is
- * just used to track 16G pages and so is a single array.  FSL-based
- * implementations may have more than one gpage size, so we need multiple
- * arrays
- */
-#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
-#define MAX_NUMBER_GPAGES	128
-struct psize_gpages {
-	u64 gpage_list[MAX_NUMBER_GPAGES];
-	unsigned int nr_gpages;
-};
-static struct psize_gpages gpage_freearray[MMU_PAGE_COUNT];
-#else
-#define MAX_NUMBER_GPAGES	1024
-static u64 gpage_freearray[MAX_NUMBER_GPAGES];
-static unsigned nr_gpages;
-#endif
-
 #define hugepd_none(hpd)	(hpd_val(hpd) == 0)
 
 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz)
@@ -210,145 +190,20 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
 	return hugepte_offset(*hpdp, addr, pdshift);
 }
 
-#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
-/* Build list of addresses of gigantic pages.  This function is used in early
- * boot before the buddy allocator is setup.
- */
-void add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
-{
-	unsigned int idx = shift_to_mmu_psize(__ffs(page_size));
-	int i;
-
-	if (addr == 0)
-		return;
-
-	gpage_freearray[idx].nr_gpages = number_of_pages;
-
-	for (i = 0; i < number_of_pages; i++) {
-		gpage_freearray[idx].gpage_list[i] = addr;
-		addr += page_size;
-	}
-}
-
-/*
- * Moves the gigantic page addresses from the temporary list to the
- * huge_boot_pages list.
- */
-int alloc_bootmem_huge_page(struct hstate *hstate)
-{
-	struct huge_bootmem_page *m;
-	int idx = shift_to_mmu_psize(huge_page_shift(hstate));
-	int nr_gpages = gpage_freearray[idx].nr_gpages;
-
-	if (nr_gpages == 0)
-		return 0;
-
-#ifdef CONFIG_HIGHMEM
-	/*
-	 * If gpages can be in highmem we can't use the trick of storing the
-	 * data structure in the page; allocate space for this
-	 */
-	m = memblock_virt_alloc(sizeof(struct huge_bootmem_page), 0);
-	m->phys = gpage_freearray[idx].gpage_list[--nr_gpages];
-#else
-	m = phys_to_virt(gpage_freearray[idx].gpage_list[--nr_gpages]);
-#endif
-
-	list_add(&m->list, &huge_boot_pages);
-	gpage_freearray[idx].nr_gpages = nr_gpages;
-	gpage_freearray[idx].gpage_list[nr_gpages] = 0;
-	m->hstate = hstate;
-
-	return 1;
-}
+#ifdef CONFIG_PPC_BOOK3S_64
 /*
- * Scan the command line hugepagesz= options for gigantic pages; store those in
- * a list that we use to allocate the memory once all options are parsed.
+ * Tracks gpages after the device tree is scanned and before the
+ * huge_boot_pages list is ready on pSeries.
  */
-
-unsigned long gpage_npages[MMU_PAGE_COUNT];
-
-static int __init do_gpage_early_setup(char *param, char *val,
-				       const char *unused, void *arg)
-{
-	static phys_addr_t size;
-	unsigned long npages;
-
-	/*
-	 * The hugepagesz and hugepages cmdline options are interleaved.  We
-	 * use the size variable to keep track of whether or not this was done
-	 * properly and skip over instances where it is incorrect.  Other
-	 * command-line parsing code will issue warnings, so we don't need to.
-	 *
-	 */
-	if ((strcmp(param, "default_hugepagesz") == 0) ||
-	    (strcmp(param, "hugepagesz") == 0)) {
-		size = memparse(val, NULL);
-	} else if (strcmp(param, "hugepages") == 0) {
-		if (size != 0) {
-			if (sscanf(val, "%lu", &npages) <= 0)
-				npages = 0;
-			if (npages > MAX_NUMBER_GPAGES) {
-				pr_warn("MMU: %lu pages requested for page "
-#ifdef CONFIG_PHYS_ADDR_T_64BIT
-					"size %llu KB, limiting to "
-#else
-					"size %u KB, limiting to "
-#endif
-					__stringify(MAX_NUMBER_GPAGES) "\n",
-					npages, size / 1024);
-				npages = MAX_NUMBER_GPAGES;
-			}
-			gpage_npages[shift_to_mmu_psize(__ffs(size))] = npages;
-			size = 0;
-		}
-	}
-	return 0;
-}
-
+#define MAX_NUMBER_GPAGES	1024
+__initdata static u64 gpage_freearray[MAX_NUMBER_GPAGES];
+__initdata static unsigned nr_gpages;
 
 /*
- * This function allocates physical space for pages that are larger than the
- * buddy allocator can handle.  We want to allocate these in highmem because
- * the amount of lowmem is limited.  This means that this function MUST be
- * called before lowmem_end_addr is set up in MMU_init() in order for the lmb
- * allocate to grab highmem.
- */
-void __init reserve_hugetlb_gpages(void)
-{
-	static __initdata char cmdline[COMMAND_LINE_SIZE];
-	phys_addr_t size, base;
-	int i;
-
-	strlcpy(cmdline, boot_command_line, COMMAND_LINE_SIZE);
-	parse_args("hugetlb gpages", cmdline, NULL, 0, 0, 0,
-			NULL, &do_gpage_early_setup);
-
-	/*
-	 * Walk gpage list in reverse, allocating larger page sizes first.
-	 * Skip over unsupported sizes, or sizes that have 0 gpages allocated.
-	 * When we reach the point in the list where pages are no longer
-	 * considered gpages, we're done.
-	 */
-	for (i = MMU_PAGE_COUNT-1; i >= 0; i--) {
-		if (mmu_psize_defs[i].shift == 0 || gpage_npages[i] == 0)
-			continue;
-		else if (mmu_psize_to_shift(i) < (MAX_ORDER + PAGE_SHIFT))
-			break;
-
-		size = (phys_addr_t)(1ULL << mmu_psize_to_shift(i));
-		base = memblock_alloc_base(size * gpage_npages[i], size,
-					   MEMBLOCK_ALLOC_ANYWHERE);
-		add_gpage(base, size, gpage_npages[i]);
-	}
-}
-
-#else /* !PPC_FSL_BOOK3E */
-
-/* Build list of addresses of gigantic pages.  This function is used in early
+ * Build list of addresses of gigantic pages.  This function is used in early
  * boot before the buddy allocator is setup.
  */
-void add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
+void __init pseries_add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
 {
 	if (!addr)
 		return;
@@ -360,10 +215,7 @@ void add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
 	}
 }
 
-/* Moves the gigantic page addresses from the temporary list to the
- * huge_boot_pages list.
- */
-int alloc_bootmem_huge_page(struct hstate *hstate)
+int __init pseries_alloc_bootmem_huge_page(struct hstate *hstate)
 {
 	struct huge_bootmem_page *m;
 	if (nr_gpages == 0)
@@ -376,6 +228,17 @@ int alloc_bootmem_huge_page(struct hstate *hstate)
 }
 #endif
 
+
+int __init alloc_bootmem_huge_page(struct hstate *h)
+{
+
+#ifdef CONFIG_PPC_BOOK3S_64
+	if (firmware_has_feature(FW_FEATURE_LPAR) && !radix_enabled())
+		return pseries_alloc_bootmem_huge_page(h);
+#endif
+	return __alloc_bootmem_huge_page(h);
+}
+
 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
 #define HUGEPD_FREELIST_SIZE \
 	((PAGE_SIZE - sizeof(struct hugepd_freelist)) / sizeof(pte_t))
diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 8a7c38b8d335..436d9721ab63 100644
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -132,8 +132,6 @@ void __init MMU_init(void)
 	 * Reserve gigantic pages for hugetlb.  This MUST occur before
 	 * lowmem_end_addr is initialized below.
 	 */
-	reserve_hugetlb_gpages();
-
 	if (memblock.memory.cnt > 1) {
 #ifndef CONFIG_WII
 		memblock_enforce_memory_limit(memblock.memory.regions[0].size);
-- 
2.13.3

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[PATCH v3 3/3] powerpc/mm/hugetlb: Allow runtime allocation of 16G.

[Aneesh Kumar K.V]

We now have GIGANTIC_PAGE on powerpc. Currently this is enabled only on
radix with 1G as gigantic hugepage size. Enable this with hash translation mode
too (ie, with 16G hugepage size). Depending on the total system memory we may
be able to allocate 16G hugepage size. This bring parity between radix and hash
translation mode. Also reduce the confusion of the user with respect to
hugetlbfs usage.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/hugetlb.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h b/arch/powerpc/include/asm/book3s/64/hugetlb.h
index 5c28bd6f2ae1..2d1ca488ca44 100644
--- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
+++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
@@ -54,9 +54,7 @@ static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
 #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
 static inline bool gigantic_page_supported(void)
 {
-	if (radix_enabled())
-		return true;
-	return false;
+	return true;
 }
 #endif
 
-- 
2.13.3

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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Michal Hocko]

On Thu 27-07-17 11:48:26, Aneesh Kumar K.V wrote:
> For ppc64, we want to call this function when we are not running as guest.

What does this mean?

> Also, if we failed to allocate hugepages, let the user know.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  include/linux/hugetlb.h | 1 +
>  mm/hugetlb.c            | 5 ++++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 0ed8e41aaf11..8bbbd37ab105 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -358,6 +358,7 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
>  			pgoff_t idx);
>  
>  /* arch callback */
> +int __init __alloc_bootmem_huge_page(struct hstate *h);
>  int __init alloc_bootmem_huge_page(struct hstate *h);
>  
>  void __init hugetlb_bad_size(void);
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bc48ee783dd9..a3a7a7e6339e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
>  	return page;
>  }
>  
> -int __weak alloc_bootmem_huge_page(struct hstate *h)
> +int alloc_bootmem_huge_page(struct hstate *h)
> +	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
> +int __alloc_bootmem_huge_page(struct hstate *h)
>  {
>  	struct huge_bootmem_page *m;
>  	int nr_nodes, node;
> @@ -2104,6 +2106,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
>  			goto found;
>  		}
>  	}
> +	pr_info("Failed to allocate hugepage of size %ld\n", huge_page_size(h));
>  	return 0;
>  
>  found:
> -- 
> 2.13.3
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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-- 
Michal Hocko
SUSE Labs

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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Liam R. Howlett]

* Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> [170727 02:18]:
> For ppc64, we want to call this function when we are not running as guest.
> Also, if we failed to allocate hugepages, let the user know.
> 
[...]
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bc48ee783dd9..a3a7a7e6339e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
>  	return page;
>  }
>  
> -int __weak alloc_bootmem_huge_page(struct hstate *h)
> +int alloc_bootmem_huge_page(struct hstate *h)
> +	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
> +int __alloc_bootmem_huge_page(struct hstate *h)
>  {
>  	struct huge_bootmem_page *m;
>  	int nr_nodes, node;
> @@ -2104,6 +2106,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
>  			goto found;
>  		}
>  	}
> +	pr_info("Failed to allocate hugepage of size %ld\n", huge_page_size(h));
>  	return 0;
>  
>  found:

There is already a call to warn the user in the
hugetlb_hstate_alloc_pages function.  If you look there, you will see
that the huge_page_size was translated into a more user friendly format
and the count prior to the failure is included.  What call path are you
trying to cover?  Also, you may want your print to be a pr_warn since it
is a failure?

Thanks,
Liam


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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Aneesh Kumar K.V]

On 07/27/2017 08:55 PM, Liam R. Howlett wrote:
> * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> [170727 02:18]:
>> For ppc64, we want to call this function when we are not running as guest.
>> Also, if we failed to allocate hugepages, let the user know.
>>
> [...]
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index bc48ee783dd9..a3a7a7e6339e 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
>>   	return page;
>>   }
>>   
>> -int __weak alloc_bootmem_huge_page(struct hstate *h)
>> +int alloc_bootmem_huge_page(struct hstate *h)
>> +	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
>> +int __alloc_bootmem_huge_page(struct hstate *h)
>>   {
>>   	struct huge_bootmem_page *m;
>>   	int nr_nodes, node;
>> @@ -2104,6 +2106,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
>>   			goto found;
>>   		}
>>   	}
>> +	pr_info("Failed to allocate hugepage of size %ld\n", huge_page_size(h));
>>   	return 0;
>>   
>>   found:
> 
> There is already a call to warn the user in the
> hugetlb_hstate_alloc_pages function.  If you look there, you will see
> that the huge_page_size was translated into a more user friendly format
> and the count prior to the failure is included.  What call path are you
> trying to cover?  Also, you may want your print to be a pr_warn since it
> is a failure?
> 

Sorry I missed that in the recent kernel. I wrote the above before the 
mentioned changes was done. I will drop the pr_info from the patch.

Thanks
-aneesh

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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Aneesh Kumar K.V]

On 07/27/2017 06:31 PM, Michal Hocko wrote:
> On Thu 27-07-17 11:48:26, Aneesh Kumar K.V wrote:
>> For ppc64, we want to call this function when we are not running as guest.
> 
> What does this mean?
> 

ppc64 guest (aka LPAR) support a different mechanism for hugetlb 
allocation/reservation. The LPAR management application called HMC can 
be used to reserve a set of hugepages and we pass the details of 
reserved pages via device tree to the guest. You can find the details in
htab_dt_scan_hugepage_blocks() . We do the memblock_reserve of the range 
and later in the boot sequence, we just add the reserved range to
huge_boot_pages.

For baremetal config (when we are not running as guest) we want to 
follow what other architecture does, that is look at the command line 
and do memblock allocation. Hence the need to call generic function 
__alloc_bootmem_huge_page() in that case.

I can add all these details in to the commit message if that makes it easy ?

-aneesh

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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Liam R. Howlett]

* Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> [170727 12:12]:
> 
> 
> On 07/27/2017 08:55 PM, Liam R. Howlett wrote:
> > * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> [170727 02:18]:
> > > For ppc64, we want to call this function when we are not running as guest.
> > > Also, if we failed to allocate hugepages, let the user know.
> > > 
> > [...]
> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > index bc48ee783dd9..a3a7a7e6339e 100644
> > > --- a/mm/hugetlb.c
> > > +++ b/mm/hugetlb.c
> > > @@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
> > >   	return page;
> > >   }
> > > -int __weak alloc_bootmem_huge_page(struct hstate *h)
> > > +int alloc_bootmem_huge_page(struct hstate *h)
> > > +	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
> > > +int __alloc_bootmem_huge_page(struct hstate *h)
> > >   {
> > >   	struct huge_bootmem_page *m;
> > >   	int nr_nodes, node;
> > > @@ -2104,6 +2106,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
> > >   			goto found;
> > >   		}
> > >   	}
> > > +	pr_info("Failed to allocate hugepage of size %ld\n", huge_page_size(h));
> > >   	return 0;
> > >   found:
> > 
> > There is already a call to warn the user in the
> > hugetlb_hstate_alloc_pages function.  If you look there, you will see
> > that the huge_page_size was translated into a more user friendly format
> > and the count prior to the failure is included.  What call path are you
> > trying to cover?  Also, you may want your print to be a pr_warn since it
> > is a failure?
> > 
> 
> Sorry I missed that in the recent kernel. I wrote the above before the
> mentioned changes was done. I will drop the pr_info from the patch.

Okay, thanks.  I didn't think there was a code path that was missed on
boot.

Cheers,
Liam

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Re: [PATCH v3 1/3] mm/hugetlb: Allow arch to override and call the weak function

[Michal Hocko]

On Thu 27-07-17 21:50:35, Aneesh Kumar K.V wrote:
> 
> 
> On 07/27/2017 06:31 PM, Michal Hocko wrote:
> >On Thu 27-07-17 11:48:26, Aneesh Kumar K.V wrote:
> >>For ppc64, we want to call this function when we are not running as guest.
> >
> >What does this mean?
> >
> 
> ppc64 guest (aka LPAR) support a different mechanism for hugetlb
> allocation/reservation. The LPAR management application called HMC can be
> used to reserve a set of hugepages and we pass the details of reserved pages
> via device tree to the guest. You can find the details in
> htab_dt_scan_hugepage_blocks() . We do the memblock_reserve of the range and
> later in the boot sequence, we just add the reserved range to
> huge_boot_pages.
> 
> For baremetal config (when we are not running as guest) we want to follow
> what other architecture does, that is look at the command line and do
> memblock allocation. Hence the need to call generic function
> __alloc_bootmem_huge_page() in that case.
> 
> I can add all these details in to the commit message if that makes it easy ?

It certainly helped me to understand the context much better. Thanks! As
you are patching a generic code this would be appropriate IMHO.
-- 
Michal Hocko
SUSE Labs

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