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 03C521EEA49; Tue, 16 Jun 2026 05:23:53 +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=1781587434; cv=none; b=fTIn7Kc/HJzk8FdQr2veJCGdUw5dHmisnsdp8P2T9j/v9ElYg6YgN5L0iucyGT39FRArVi/fqmLZC6RVcGeiHBkfla5PuKcL41LRqJF7TSiBS+M5QBSboUPD6baPCE0mCLdDvDMaZJ+Nc64YLzKiS747jYP3zNO93uWcDR3xG9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781587434; c=relaxed/simple; bh=QxH5qOTe/YG8RUrLabSR6EzwwhszMJWlBSsZ8Mep+KM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jQbxYWsC+bWlwy5IrsnyGH2P9SZZ1He4A++GEkIblW0TIwTioPLzPqzrfcsGRthwyCmXz7sRtHLfHdo0EAanKfaQ7o3Jn0wOXE/fRiHJggu1DQe+eNEJt3eJwsGwivBRHxRYEzRArd+Iv0vHf3VibONlVKugs5EujC7G8Q/dZjg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kG6Aojvq; 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="kG6Aojvq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19C171F000E9; Tue, 16 Jun 2026 05:23:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781587433; bh=QxH5qOTe/YG8RUrLabSR6EzwwhszMJWlBSsZ8Mep+KM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kG6Aojvqf2S6KeFzC84yjhG9VPPJBAAYbiSvfpHpD23VaszvHKOoEq1AKHv7GwTXm Rno48p8+6FfjRUIJn2gOhE14/u4zwiqzzhnJi6MJBBZtTJMoJyb52CYCJ0tZ238uv/ wZDyjBqf7GPF1gzLERDXSkItxwy8/cZCjbbyQhdRFwiWgRR8d66Tgd7KgLtlOJxEt0 7AtmV9S1Zxk6Dihh3DANuMrX8oyOh1Osfhlz91nfVtaM21z9vwEPdOnnBoUAsjz7BJ s250yj4kdW/xFc8WMx57LqE5tduMZD0g4rXh2jFwp5CCdasx0njIzJWr0uAtuAHHzn 5H4saBl9Of6eA== Message-ID: <327e2eeb-b9e4-44b8-a933-9ad783d34ed7@kernel.org> Date: Tue, 16 Jun 2026 14:23:45 +0900 Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH for-next v3 1/9] slub_kunit: fall back to SW perf events when HW PMU is not available To: Alexei Starovoitov , Vlastimil Babka , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Andrii Nakryiko , Puranjay Mohan , Amery Hung , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Pedro Falcato , Suren Baghdasaryan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, rcu@vger.kernel.org, bpf@vger.kernel.org References: <20260615-kfree_rcu_nolock-v3-0-70a54f3775bb@kernel.org> <20260615-kfree_rcu_nolock-v3-1-70a54f3775bb@kernel.org> Content-Language: en-US From: Harry Yoo In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------rP7fGiX08FjSBMo4mTOXAahH" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------rP7fGiX08FjSBMo4mTOXAahH Content-Type: multipart/mixed; boundary="------------3SbEaLSYHxVUNx3lobFuFikg"; protected-headers="v1" From: Harry Yoo To: Alexei Starovoitov , Vlastimil Babka , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Andrii Nakryiko , Puranjay Mohan , Amery Hung , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Pedro Falcato , Suren Baghdasaryan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, rcu@vger.kernel.org, bpf@vger.kernel.org Message-ID: <327e2eeb-b9e4-44b8-a933-9ad783d34ed7@kernel.org> Subject: Re: [PATCH for-next v3 1/9] slub_kunit: fall back to SW perf events when HW PMU is not available References: <20260615-kfree_rcu_nolock-v3-0-70a54f3775bb@kernel.org> <20260615-kfree_rcu_nolock-v3-1-70a54f3775bb@kernel.org> In-Reply-To: --------------3SbEaLSYHxVUNx3lobFuFikg Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 6/16/26 5:01 AM, Alexei Starovoitov wrote: > On Mon Jun 15, 2026 at 4:05 AM PDT, Harry Yoo (Oracle) wrote: >> slub_kunit uses hardware perf events to invoke _nolock() APIs from NMI= >> context. However, creating a HW perf event fails when there is no >> hardware PMU, or when running in a virtualized environment without a >> virtual PMU configured. >> >> Since tests are often performed in virtualized environments, fall back= >> to a SW perf event so that the test can still run, even if it cannot >> cover IRQ-disabled sections. >=20 > Frankly, I wouldn't bother with this fallback, since it completely miss= es > irq disabled section which is the one to test with *_nolock(). Right, it only covers percpu sheaves locks. > VMs need to configured properly. Even nested VMs support > PERF_COUNT_HW_CPU_CYCLES. And now that even VMs that are not properly configured can test it using kprobe with _some_ coverage, we don't really need the fallback. Will drop the fallback. > Also in overflow_handler_test_nolock() > I would add > even->hw.interrupts =3D 0; > to the end to make sure it actually stress tests things. > Without it NMIs are not firing quickly enough. Will do. Thanks! --=20 Cheers, Harry / Hyeonggon --------------3SbEaLSYHxVUNx3lobFuFikg-- --------------rP7fGiX08FjSBMo4mTOXAahH Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQQQ1ub6gR5ogjaKRmOGXBN6rc5S1gUCajDd4gAKCRCGXBN6rc5S 1mG/AQD+6bsjWeb6zEOVUA7ge6HdSL9IweB0GLSChJQcA/DgyAEAmysfWrQosnQc o3L/HYTVOn3F0X9ZEn1ONdfMyvCtdgk= =qy9q -----END PGP SIGNATURE----- --------------rP7fGiX08FjSBMo4mTOXAahH--