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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=K3Zn69FG; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ABC88606A319 for ; Tue, 20 Oct 2026 07:59:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=K3Zn69FG Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB8E51F000C4; Tue, 20 Oct 2026 07:59:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792483151; bh=ReBTcrDImQvhoa5yHIWdOL2JpqjCmSuJOVv23tlb0UA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=K3Zn69FGWwSiJtnA3FBjGGoXJSaQ410NJ80DjvSu6xdbeDuevOL9AACByNV9xTbWq o1J5l6e6+tCNtsnjE89KTNAGa4Lxg5PjNQ3TcF3VXEG21gwhgfJEATg3/IIt9tEc66 GJXmr+tN0rbXuqI4CE+7oAr1gZVH7BPL2W4HoyDbhMTuyHOZfNgC2AF5XZCMRCrQYA WKrgr+M8EgQ19bpl4A8CTpaNg4Qazlsnj8fxenfx9YSQdnaAph96gxTN7GzGa/3r9W IfKRxOxomD4OQCsbAf+EXogLaKsngv2775eNZwjfOvRUu0BspyMnzUWe72nWkaoNYR 0CXX9OuWyKmTA== Message-ID: Date: Tue, 20 Oct 2026 09:59:07 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [patch v5] mm: vmstat_kunit: add synthetic benchmark for mm stats To: David Rientjes , Andrew Morton Cc: Christoph Lameter , Vlastimil Babka , Mathieu Desnoyers , Sarthak Sharma , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <920ba123-077e-c42d-ebdf-a5effccf2073@google.com> <8b077a83-3f79-cbfa-0273-e086b0e51ae4@google.com> 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 10/17/26 00:35, David Rientjes wrote: > On Fri, 9 Oct 2026, David Rientjes wrote: > >> From: Christoph Lameter >> >> Add a synthetic benchmark that can be used to measure performance of MM >> statistics. This is used to analyze any improvements or regressions in >> functions that are frequently used in hot code paths. >> >> This is the first of three tests that measure the execution times of >> critical MM functions anticipated to be used by developers to measure the >> impact of any core changes that would end up causing workload performance >> issues. Vmstats are embedded into MM hotpaths, so any regression can >> cause performance and scalability impact for users. Google has carried >> these tests internally and kept them updated since Christoph posted them >> back in 2009 for this purpose. >> >> This can also be used to detect regressions over time, from kernel >> version to kernel version, independent of development use cases. >> >> 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 >> --- >> v5: >> - added dependency on CONFIG_VM_EVENT_COUNTERS >> - expanded commit description >> >> Once we're happy with this change, I'll apply the same treatment to the >> proposed pgalloc and slab tests. >> > > I've added the rationale for the change to the commit description as > primairly being used by developers to benchmark and monitor any > regressions in functions that are known to be super hot and impact > workload performance. > > This is the simplest of the three tests that Christoph provided back in > 2009, the others are pgalloc and slab tests, see > https://marc.info/?l=linux-mm&m=178547194364290 and > https://marc.info/?l=linux-mm&m=178547193264283 for those. Based on the > feedback to move to kunit, I forked this one off independently because it > was the simplest to address all the feedback and pave the way for the > other two to be upstreamed afterwards. > > Is this acceptable for merge? If we're happy with this, I'll move onto > the pgalloc and slab variants. Works for me. The tests are rather small and I see value in them. -- Cheers, David