From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3C7DE33F3; Wed, 12 Nov 2025 00:43:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762908197; cv=none; b=Pg4DOlKoUhPxBMkIR/WyRiswtyRSeNuSJJWwEJmWU8nilaoH/eRojBF/3cLYMHpemWbxVYilLJrny9qxDeNVuoA1t6qxoEcoUF3CQvJdDzlzuzmok4p4TRLWRgvvf5Jb7PEjptZWTL16y317gfPJXYOXUAzCeqr5c1o61X0Fk0g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762908197; c=relaxed/simple; bh=atpFUL7pJYRuvuflts9DoB2NTZpWxZJSKckn+I2ruEU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=E1mF8FAKYQ7zBXk6htCVL8bjf7sasGhLb+ViZ/lUgJdkVpw1RcHc3AVmib25osVRDQZJ/SOP97vYc0g4TMaMgcFg+OyBI4HjXZX/ahMRCprEiaCzz53WdGuesZ5iiQaNK4Z14EGuxCKFowxcf5jqF5DWPX0dm4ihrXhteHBPw84= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=azgas3dy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="azgas3dy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99DE2C116D0; Wed, 12 Nov 2025 00:43:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762908196; bh=atpFUL7pJYRuvuflts9DoB2NTZpWxZJSKckn+I2ruEU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=azgas3dy3XFARqqEvidJa0zDJCCN7XnLwbpkIQFjp6vDAvrACAJaLkMLIHlYDAevM 5qOm3TBzkj+RieWN/Dy5D7LLJF3nKDdvz3bWveIYxl2W1DFI3zbNO9o1wZVaDSWyhC mcebqrnLATC0AgtqvMHdolQt3p++6aL4WisX1NPbZRvej6HV6+fQBIUBcjagTlXly0 ham7uuRIpfi6YVap8OBvO+fPt0YvNoqpMeyG7OdtjlDoMwY38pq32tfAx5sSWtZBag YtNUe+2WRCNNE3TOw893hcCA1TmEaUNvBkhQGq1jilSUWKoNCbERS1ODymBfaU0VsH lKl36mF/+Ne8Q== Date: Tue, 11 Nov 2025 16:43:13 -0800 From: Namhyung Kim To: "Chen, Zide" Cc: Arnaldo Carvalho de Melo , Ian Rogers , James Clark , Jiri Olsa , Adrian Hunter , Peter Zijlstra , Ingo Molnar , LKML , linux-perf-users@vger.kernel.org Subject: Re: [PATCH] perf tools: Fix missing feature check for inherit + SAMPLE_READ Message-ID: References: <20251111075944.2328021-1-namhyung@kernel.org> <7ea7c72d-7570-4eca-8a8a-d8f93363691e@intel.com> <3f2e834b-36d1-4227-b1bd-843e824ac353@intel.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3f2e834b-36d1-4227-b1bd-843e824ac353@intel.com> On Tue, Nov 11, 2025 at 02:36:19PM -0800, Chen, Zide wrote: > > > On 11/11/2025 2:31 PM, Namhyung Kim wrote: > > On Tue, Nov 11, 2025 at 12:03:22PM -0800, Chen, Zide wrote: > >> > >> > >> On 11/11/2025 11:40 AM, Namhyung Kim wrote: > >>> On Tue, Nov 11, 2025 at 11:13:20AM -0800, Chen, Zide wrote: > >>>> > >>>> > >>>> On 11/10/2025 11:59 PM, Namhyung Kim wrote: > >>>>> It should also have PERF_SAMPLE_TID to enable inherit and PERF_SAMPLE_READ > >>>>> on recent kernels. Not having _TID makes the feature check wrongly detect > >>>>> the inherit and _READ support. > >>>>> > >>>>> It was reported that the following command failed due to the error in > >>>>> the missing feature check on Intel SPR machines. > >>>>> > >>>>> $ perf record -e '{cpu/mem-loads-aux/S,cpu/mem-loads,ldlat=3/PS}' -- ls > >>>>> Error: > >>>>> Failure to open event 'cpu/mem-loads,ldlat=3/PS' on PMU 'cpu' which will be removed. > >>>>> Invalid event (cpu/mem-loads,ldlat=3/PS) in per-thread mode, enable system wide with '-a'. > >>>>> > >>>>> Fixes: 3b193a57baf15c468 ("perf tools: Detect missing kernel features properly") > >>>>> Reported-by: "Chen, Zide" > >>>>> Signed-off-by: Namhyung Kim > >>>>> --- > >>>>> tools/perf/util/evsel.c | 2 +- > >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > >>>>> index 67a898cda86ab559..989c56d4a23f74f4 100644 > >>>>> --- a/tools/perf/util/evsel.c > >>>>> +++ b/tools/perf/util/evsel.c > >>>>> @@ -2474,7 +2474,7 @@ static bool evsel__detect_missing_features(struct evsel *evsel, struct perf_cpu > >>>>> /* Please add new feature detection here. */ > >>>>> > >>>>> attr.inherit = true; > >>>>> - attr.sample_type = PERF_SAMPLE_READ; > >>>>> + attr.sample_type = PERF_SAMPLE_READ | PERF_SAMPLE_TID; > >>>> > >>>> > >>>> Seems this could have some unintended side effects. For example, > >>>> consider a :ppp event with PERF_SAMPLE_READ and inherit attributes > >>>> running on a system where the maximum precise_ip is 2: > >>>> > >>>> - It fails to open the event on the first attempt; > >>>> - It goes through the inherit_sample_read detection and fails again > >>>> after removing inherit; > >>> > >>> This is not what we want. The kernel supports inherit + SAMPLE_READ > >>> so it should not remove the inherit bit. > >>> > >>> > >>>> - Finally, it succeeds after falling back to precision 2 — but the > >>>> inherit attribute has been unexpectedly removed. > >>> > >>> So it'll fallback to precision 2 without removing inherit. > >>> > >>>> > >>>> I may have missed something, but I don’t quite understand why commit > >>>> 3b193a57baf15 ("perf tools: Detect missing kernel features properly") > >>>> performs the check on a dummy evsel instead of the original one. In this > >>>> way, it might incorrectly fall back an attribute that doesn’t actually help. > >>> > >>> Because different platforms have different limitations on hardware > >>> events. You cannot simply use current event for kernel feature check > >>> since it can result in wrong decisions due to the limitation. So we > >>> picked the software event to avoid the hardware characteristics and to > >>> focus on kernel features. > >>> > >>>> > >>>> This means evsel__detect_missing_features() could theoretically roll > >>>> back a feature that might not actually work. Given that it cannot > >>>> restore the original evsel state after a failed attempt, side effects > >>>> may occur. > >>> > >>> The purpose is to turn off the non-supported features only and try with > >>> other settings like precise_ip and exclude_kernels and so on. > >> > >> OK, thanks! > > > > Can you please confirm if this patch fixes your problem? > > Yes, it works! Thanks, I'll add your Tested-by then! Namhyung