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 EBF2248F01B; Tue, 8 Sep 2026 22:08:18 +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=1788905300; cv=none; b=Ah4/FFukAWRWOsfG9fsHpEtaEGAG4vRVH8MO2kJSRtoMQ0gHotlnJ+yLoWis/poqNEszQsuoJ31j/tv3pdeTnfj/p0e2B8WIvovimJZkNy6zhKXDW7u/kqBu8tu1hNAFpvTPx+jn71RtheuZ3aO73UGnl9xtYrTvY51hJcSkxxU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788905300; c=relaxed/simple; bh=fGgTZvjY36/wB/uAxX25FOYeTblqb7YMtdvqvdINyy0=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=GaiBe9ZLP3u1j7Ql5O674H6wgsPeUI2EFDxkVtVyohm6FAASRDYu4MEsKiLr/MYUvjDnbfdcupptUzzEm3l2yL9FEeddLMFsUJF7Zo12UY/YgKbu4Z3nDVFvzojjSsfLqEul+vnQC10PK4+8zKAANL76rScu65XbGS1MgSMtEuM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XH7flFfe; 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="XH7flFfe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 422781F00A3A; Tue, 8 Sep 2026 22:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788905298; bh=dOiFhq8I88BVcZtuFbjPLOvWG1Y1WY5skTD6v32H6kM=; h=Date:From:Subject:To:Cc:References:In-Reply-To; b=XH7flFfei05ZPRPwExgckouFMZOyTeZMb3U1eLh6GGQMCNVjQY83rYsO+MV4uN9FH /kHyhzpqTS2DSW15FpCJUzVln6rYt8tA6Hbag8H48TAYCm0iQ9jH/xHj1XaSUStpN+ yK5KTTmV8W2imROzeUVVqj905fsq/6vd7m6P8b7xsFBnqQce7Wjibp6SjzbVxgusdp siPdifxC6403siNDmzxprjXppdgnVaQTQO3Rs+d+4VP3HDVLrMIXmnICfVt6Rl26zi oP3SY+qxSDmqAR6RcP/ccWNuW1cSxX+FCq8sKrnktcKb/9lRK4vN3XUNA0efSh8Oiv guMG/3m+/F0xA== Message-ID: <28beb73e-5cee-4263-bd72-95e15f3aa028@kernel.org> Date: Tue, 8 Sep 2026 23:08:14 +0100 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Quentin Monnet Subject: Re: [PATCH bpf-next v3 1/3] bpftool: Track perf counter snapshot state To: Mykyta Yatsenko , bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com, linux-perf-users@vger.kernel.org, acme@kernel.org, namhyung@kernel.org Cc: Mykyta Yatsenko References: <20260908-bpftool_cyles_per_run-v3-0-60e86f325c35@meta.com> <20260908-bpftool_cyles_per_run-v3-1-60e86f325c35@meta.com> Content-Language: en-GB In-Reply-To: <20260908-bpftool_cyles_per_run-v3-1-60e86f325c35@meta.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 2026-09-08 07:27 UTC-0700 ~ Mykyta Yatsenko > From: Mykyta Yatsenko > > A perf counter can be zero at fentry. PMU multiplexing can schedule the > event during the BPF program. The old counter check then drops a valid > sample. > > Use an armed flag to track each successful fentry snapshot. Reset all > flags before new reads. The fexit path clears each flag when it consumes > the snapshot. > > Fixes: 47c09d6a9f67 ("bpftool: Introduce "prog profile" command") > Signed-off-by: Mykyta Yatsenko Acked-by: Quentin Monnet