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SubjectRe: [PATCH 1/3] mm: refactor __vunmap() to avoid duplicated call to find_vm_area()
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On 2/25/19 9:30 PM, Roman Gushchin wrote:
> __vunmap() calls find_vm_area() twice without an obvious reason:
> first directly to get the area pointer, second indirectly by calling
> remove_vm_area(), which is again searching for the area.
>
> To remove this redundancy, let's split remove_vm_area() into
> __remove_vm_area(struct vmap_area *), which performs the actual area
> removal, and remove_vm_area(const void *addr) wrapper, which can
> be used everywhere, where it has been used before.
>
> On my test setup, I've got 5-10% speed up on vfree()'ing 1000000
> of 4-pages vmalloc blocks.
>
> Perf report before:
> 22.64% cat [kernel.vmlinux] [k] free_pcppages_bulk
> 10.30% cat [kernel.vmlinux] [k] __vunmap
> 9.80% cat [kernel.vmlinux] [k] find_vmap_area
> 8.11% cat [kernel.vmlinux] [k] vunmap_page_range
> 4.20% cat [kernel.vmlinux] [k] __slab_free
> 3.56% cat [kernel.vmlinux] [k] __list_del_entry_valid
> 3.46% cat [kernel.vmlinux] [k] smp_call_function_many
> 3.33% cat [kernel.vmlinux] [k] kfree
> 3.32% cat [kernel.vmlinux] [k] free_unref_page
>
> Perf report after:
> 23.01% cat [kernel.kallsyms] [k] free_pcppages_bulk
> 9.46% cat [kernel.kallsyms] [k] __vunmap
> 9.15% cat [kernel.kallsyms] [k] vunmap_page_range
> 6.17% cat [kernel.kallsyms] [k] __slab_free
> 5.61% cat [kernel.kallsyms] [k] kfree
> 4.86% cat [kernel.kallsyms] [k] bad_range
> 4.67% cat [kernel.kallsyms] [k] free_unref_page_commit
> 4.24% cat [kernel.kallsyms] [k] __list_del_entry_valid
> 3.68% cat [kernel.kallsyms] [k] free_unref_page
> 3.65% cat [kernel.kallsyms] [k] __list_add_valid
> 3.19% cat [kernel.kallsyms] [k] __purge_vmap_area_lazy
> 3.10% cat [kernel.kallsyms] [k] find_vmap_area
> 3.05% cat [kernel.kallsyms] [k] rcu_cblist_dequeue
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Matthew Wilcox <willy@infradead.org>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

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