linux-kernel - Re: [PATCH 2/3] mm/vmalloc: Switch to bulk allocator in __vmalloc_area

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Date:   Mon, 17 May 2021 09:24:50 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 2/3] mm/vmalloc: Switch to bulk allocator in
 __vmalloc_area_node()

On Sun, May 16, 2021 at 10:20:55PM +0200, Uladzislau Rezki (Sony) wrote:
> Recently there has been introduced a page bulk allocator for
> users which need to get number of pages per one call request.
> 
> For order-0 pages switch to an alloc_pages_bulk_array_node()
> instead of alloc_pages_node(), the reason is the former is
> not capable of allocating set of pages, thus a one call is
> per one page.
> 
> Second, according to my tests the bulk allocator uses less
> cycles even for scenarios when only one page is requested.
> Running the "perf" on same test case shows below difference:
> 
> <default>
>   - 45.18% __vmalloc_node
>      - __vmalloc_node_range
>         - 35.60% __alloc_pages
>            - get_page_from_freelist
>                 3.36% __list_del_entry_valid
>                 3.00% check_preemption_disabled
>                 1.42% prep_new_page
> <default>
> 
> <patch>
>   - 31.00% __vmalloc_node
>      - __vmalloc_node_range
>         - 14.48% __alloc_pages_bulk
>              3.22% __list_del_entry_valid
>            - 0.83% __alloc_pages
>                 get_page_from_freelist
> <patch>
> 
> The "test_vmalloc.sh" also shows performance improvements:
> 
> fix_size_alloc_test_4MB   loops: 1000000 avg: 89105095 usec
> fix_size_alloc_test       loops: 1000000 avg: 513672   usec
> full_fit_alloc_test       loops: 1000000 avg: 748900   usec
> long_busy_list_alloc_test loops: 1000000 avg: 8043038  usec
> random_size_alloc_test    loops: 1000000 avg: 4028582  usec
> fix_align_alloc_test      loops: 1000000 avg: 1457671  usec
> 
> fix_size_alloc_test_4MB   loops: 1000000 avg: 62083711 usec
> fix_size_alloc_test       loops: 1000000 avg: 449207   usec
> full_fit_alloc_test       loops: 1000000 avg: 735985   usec
> long_busy_list_alloc_test loops: 1000000 avg: 5176052  usec
> random_size_alloc_test    loops: 1000000 avg: 2589252  usec
> fix_align_alloc_test      loops: 1000000 avg: 1365009  usec
> 
> For example 4MB allocations illustrates ~30% gain, all the
> rest is also better.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>

FWIW, it passed build and boot tests.

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs