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b=YdzZPRu9Nn0yBypW8uscTyI+AB2opAITNSPrdORh14BQox3KliXHTMyLZ4Wz+B6+q 1C5kScmdm4wfBDFaiKHL45jdU/6w8SaNSwndJvzeUkMK+KAhlnBCHWuaD1fMn5Zs5F khkw5V70JKFEQzQxfgRzkarMvRCPP1ZAGEvxP/EfQhqMy48Woofn8hrdotzix5/xf0 I8bqdgjebm8rMHCn2sxnURIKQ3wrGD9Q2DmqPtIDUWk9dnrfrXi2Tw1LxCCTZLlQtf A7194sOUxY85lTZBouNzAO69mlSBlkGZBRNxPSWiMwiHfng1cxXzHwVn8r6gg8QDWY r83xww0IIyJHg== Message-ID: Date: Mon, 28 Sep 2026 14:19:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [patch v4] mm: vmstat_kunit: add synthetic benchmark for vm stats To: David Rientjes , Andrew Morton Cc: Christoph Lameter , Vlastimil Babka , Mathieu Desnoyers , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sarthak Sharma References: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C8632C0005 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 5pws1xkjhsdhor6umxzx8bqcd6pdq3dw X-HE-Tag: 1790597982-143703 X-HE-Meta: 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 8eK1tvff 8DVM7kDgGWe8YbzgfwPphn8YoPaTTmJO8VTF1tgIOo1rIWQjkEQH8Vglr7VBuUhU94h50k9mfwwy3gUOhMY/66MrUMszJwCN8+Rk+V0MzUsaNYVkAhUqgwBvp304KTGIQjpgAgu6+Vn//33TjnqE8zZMEmL7go6VZnggZqFhD0U5CRzM3BLT6mJzeNToKQyQad32A526crcvkLGbvgqWE2K1zkwgERYs6tBet0TCNqifigYkyv+D6dMa0IG4X6ls+WtDS9fg3J1FQHBamKedcgiQaqoHVffggN8GX1sZJV8V43yjhIKxyFv0FSXXZMjv0A1c+yghOhtJ+B8OsZ406+SMl8pW1U3NgbkGbibsTVbr4oUsl6nqONSuDwtU8d4YN8d0q05LvMbSphXQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/18/26 22:39, David Rientjes wrote: > From: Christoph Lameter > > Add a synthetic benchmark that can be used to measure performance of VM > statistics. This is used to analyze any improvements or regressions in > functions that are frequently used in hot code paths. > > The test is run by KUnit or doing modprobe vmstat_kunit directly. > > Sample output: > KTAP version 1 > 1..1 > KTAP version 1 > # Subtest: vmstat > # module: vmstat_kunit > 1..3 > # vmstat_test_inc_dec_zone_page_state: 10000 ops: inc_zone_page_state -> 8 cycles (4 ns/op), dec_zone_page_state -> 9 cycles (4 ns/op) > ok 1 vmstat_test_inc_dec_zone_page_state > # vmstat_test_interleaved_zone_page_state: 10000 ops: inc/dec pair -> 17 cycles (8 ns/op) > ok 2 vmstat_test_interleaved_zone_page_state > # vmstat_test_count_vm_event: 10000 ops: count_vm_event -> 4 cycles (2 ns/op) > ok 3 vmstat_test_count_vm_event > # vmstat: pass:3 fail:0 skip:0 total:3 > # Totals: pass:3 fail:0 skip:0 total:3 > ok 1 vmstat > > Assisted-by: Gemini:gemini-3.8-flash > Signed-off-by: Christoph Lameter > Signed-off-by: David Rientjes > --- > v4: > - included sample output in the commit description > - switched to NR_MLOCK which is display only so no side effects > - remove unnecessary "rem" variable > > Once we're happy with this change, I'll apply the same treatment to the > proposed pgalloc and slab tests. > > MAINTAINERS | 1 + > mm/Kconfig | 11 +++ > mm/Makefile | 1 + > mm/tests/vmstat_kunit.c | 157 ++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 170 insertions(+) > create mode 100644 mm/tests/vmstat_kunit.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 3b2eb2a7a89a..de09076d91b9 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -17161,6 +17161,7 @@ F: mm/ptdump.c > F: mm/sparse-vmemmap.c > F: mm/sparse.c > F: mm/sparse.h > +F: mm/tests/vmstat_kunit.c > F: mm/util.c > F: mm/vmpressure.c > F: mm/vmstat.c > diff --git a/mm/Kconfig b/mm/Kconfig > index 604c58199acb..2d021fb5ace6 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1511,6 +1511,17 @@ config LAZY_MMU_MODE_KUNIT_TEST > > If unsure, say N. > > +config VMSTAT_KUNIT_TEST > + tristate "KUnit test for VM statistics" if !KUNIT_ALL_TESTS > + depends on KUNIT > + default KUNIT_ALL_TESTS > + help > + Enable this option to test and benchmark the performance of VM > + statistics updates (zone page state and VM event counters), which > + are used frequently in hot memory management code paths. > + > + If unsure, say N. > + > source "mm/damon/Kconfig" > > endmenu > diff --git a/mm/Makefile b/mm/Makefile > index e7245cb88c66..3d4f2c43b8d3 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -147,4 +147,5 @@ obj-$(CONFIG_SHRINKER_DEBUG) += shrinker_debug.o > obj-$(CONFIG_EXECMEM) += execmem.o > obj-$(CONFIG_TMPFS_QUOTA) += shmem_quota.o > obj-$(CONFIG_LAZY_MMU_MODE_KUNIT_TEST) += tests/lazy_mmu_mode_kunit.o > +obj-$(CONFIG_VMSTAT_KUNIT_TEST) += tests/vmstat_kunit.o > obj-$(CONFIG_MEM_ALLOC_PROFILING) += alloc_tag.o > diff --git a/mm/tests/vmstat_kunit.c b/mm/tests/vmstat_kunit.c > new file mode 100644 > index 000000000000..899c957091d1 > --- /dev/null > +++ b/mm/tests/vmstat_kunit.c > @@ -0,0 +1,157 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * KUnit synthetic performance benchmark for VM statistics. > + * > + * (C) 2009 Linux Foundation, Christoph Lameter > + * (C) 2026 Google LLC, David Rientjes > + */ > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define TEST_COUNT 10000 > + > +static void vmstat_test_free_page(void *arg) > +{ > + __free_page((struct page *)arg); > +} > + > +/* > + * Test 1: Sequential inc_zone_page_state() followed by dec_zone_page_state(). > + * Net change to zone counters is 0. > + */ > +static void vmstat_test_inc_dec_zone_page_state(struct kunit *test) > +{ > + struct page *page; > + cycles_t time1, time2, time; > + u64 t1_ns, t2_ns; > + u64 inc_cycles, dec_cycles; > + u64 inc_ns, dec_ns; > + unsigned int i; > + > + page = alloc_page(GFP_KERNEL); > + KUNIT_ASSERT_NOT_NULL(test, page); > + KUNIT_ASSERT_EQ(test, kunit_add_action_or_reset(test, vmstat_test_free_page, page), 0); > + > + /* Benchmark inc_zone_page_state() */ > + time1 = get_cycles(); > + t1_ns = ktime_get_ns(); > + for (i = 0; i < TEST_COUNT; i++) > + inc_zone_page_state(page, NR_MLOCK); Just curious, could some compiler optimizations here change the picture, and doing the average would not actually be representative? Not sure if a barrier() would reliably avoid that. Maybe not relevant today, but I do wonder if we should take care that it stays that way. Applies to all cases below where we loop. This looks much cleaner to me, thanks! -- Cheers, David