From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E976379C42 for ; Mon, 28 Sep 2026 12:19:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790597984; cv=none; b=P7Et2S+TNkQX29obOR3v1qC7SfYMcA4pzUTug5DnaLNB8Y8zSnKwMO390SU7xhCT0TX1Hz8CyhYDLpUwqIVJ/tM7kwmFPqpSKrPg89r3i4/h2z8LK0sNrx1VTnQiRVUGuyZfTL8rj7bTGFraJHplhu1YWUt62qJU/k5YoKCigi0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790597984; c=relaxed/simple; bh=+odSPGHMvNELUkeAuN53FWH8WbosA6kggeCd89bJGhc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LLGlnoQpTCTVYmlQ7exCvpszrmg5zRancrtOQdR6NitHjwgy4GRTs2qLslHmEwyeJYZnwdncMEsPGIoGoEBiUfRqe5i2leCTT4YoUwcrv8pUIzSWbbNtEXouDcjVkMRieEljrCb5j0h+VghKQ37WF0cnnhXipI//+OJXOAHkngU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YdzZPRu9; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YdzZPRu9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B63181F000FF; Mon, 28 Sep 2026 12:19:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790597982; bh=Ohwros3KJBzi0jPBOqdA6bXPhNWwE/XNWT6NGKqiiJQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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