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SubjectRe: [v2 0/6] mm/memblock: Skip prep and initialization of struct pages freed later by HVO
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On 30/07/2023 16:16, Usama Arif wrote:
> If the region is for gigantic hugepages and if HVO is enabled, then those
> struct pages which will be freed later by HVO don't need to be prepared and
> initialized. This can save significant time when a large number of hugepages
> are allocated at boot time.
>
> For a 1G hugepage, this series avoid initialization and preparation of
> 262144 - 64 = 262080 struct pages per hugepage.
>
> When tested on a 512G system (which can allocate max 500 1G hugepages), the
> kexec-boot time with HVO and DEFERRED_STRUCT_PAGE_INIT enabled without this
> patchseries to running init is 3.9 seconds. With this patch it is 1.2 seconds.
> This represents an approximately 70% reduction in boot time and will
> significantly reduce server downtime when using a large number of
> gigantic pages.
>
> Thanks,
> Usama
>

There were build errors reported by kernel-bot when
CONFIG_HUGETLBFS/CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is disabled due to
patches 5 and 6 which should be fixed by below diff. Will wait for
review and include it in next revision as its a trivial diff

diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index 3fff6f611c19..285b59b71203 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -38,6 +38,8 @@ static inline unsigned int
hugetlb_vmemmap_optimizable_size(const struct hstate
return 0;
return size > 0 ? size : 0;
}
+
+extern bool vmemmap_optimize_enabled;
#else
static inline int hugetlb_vmemmap_restore(const struct hstate *h,
struct page *head)
{
@@ -58,6 +60,8 @@ static inline bool vmemmap_should_optimize(const
struct hstate *h, const struct
return false;
}

+static bool vmemmap_optimize_enabled = false;
+
#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */

static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
@@ -65,6 +69,4 @@ static inline bool hugetlb_vmemmap_optimizable(const
struct hstate *h)
return hugetlb_vmemmap_optimizable_size(h) != 0;
}

-extern bool vmemmap_optimize_enabled;
-
#endif /* _LINUX_HUGETLB_VMEMMAP_H */
diff --git a/mm/internal.h b/mm/internal.h
index 692bb1136a39..c3321afa36cb 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1106,7 +1106,7 @@ struct vma_prepare {
#ifdef CONFIG_HUGETLBFS
void __init hugetlb_hstate_alloc_gigantic_pages(void);
#else
-static inline void __init hugetlb_hstate_alloc_gigantic_pages(void);
+static inline void __init hugetlb_hstate_alloc_gigantic_pages(void)
{
}
#endif /* CONFIG_HUGETLBFS */

> [v1->v2]:
> - (Mike Rapoport) Code quality improvements (function names, arguments,
> comments).
>
> [RFC->v1]:
> - (Mike Rapoport) Change from passing hugepage_size in
> memblock_alloc_try_nid_raw for skipping struct page initialization to
> using MEMBLOCK_RSRV_NOINIT flag
>
>
>
> Usama Arif (6):
> mm: hugetlb: Skip prep of tail pages when HVO is enabled
> mm: hugetlb_vmemmap: Use nid of the head page to reallocate it
> memblock: pass memblock_type to memblock_setclr_flag
> memblock: introduce MEMBLOCK_RSRV_NOINIT flag
> mm: move allocation of gigantic hstates to the start of mm_core_init
> mm: hugetlb: Skip initialization of struct pages freed later by HVO
>
> include/linux/memblock.h | 9 +++++
> mm/hugetlb.c | 71 +++++++++++++++++++++++++---------------
> mm/hugetlb_vmemmap.c | 6 ++--
> mm/hugetlb_vmemmap.h | 18 +++++++---
> mm/internal.h | 9 +++++
> mm/memblock.c | 45 +++++++++++++++++--------
> mm/mm_init.c | 6 ++++
> 7 files changed, 118 insertions(+), 46 deletions(-)
>

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