From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f43.google.com (mail-ej1-f43.google.com [209.85.218.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A69C230AAD7 for ; Mon, 13 Oct 2025 20:41:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760388091; cv=none; b=t7DByzeNswQxo56JYFKCh+IRJs+CvY0a8E0QGfd+OuYztpCnlwvTM4GnndBXoZqZeBWl0voIOMvRSBvl58KnbJcsUOjCbkTx2Fcpfz0P/kjM/EJ485wtofbyJY8c57/+9ERzEiFFPsYYG2lRHT+tB5mPOeL9GgCBO9ZY3K+NVQw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760388091; c=relaxed/simple; bh=GsSWfFlXkBsxiUZoCz6mvqXlZhLEzpwSFRwMJKX6ek4=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=t2HWrk1Qdfj5SsI+RdS6b+GoYZL+bOwWUX9KCPcNnci9Bo1gYXVN1V1dw5iyhGk8h9Zb4lhAPk6tP2gOcHGNbPLMuhl1bWdglA+i9nKKLuW9mu1KrAWdCnLQfGAeaTnvzvqQ912xoP5/gLS02ur6p9tArrflbz4hnv2oovsW9Pg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=UxSNtELP; arc=none smtp.client-ip=209.85.218.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UxSNtELP" Received: by mail-ej1-f43.google.com with SMTP id a640c23a62f3a-b403bb7843eso995640766b.3 for ; Mon, 13 Oct 2025 13:41:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1760388088; x=1760992888; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=wCLtlY+GpSdapckAq80Uoda7FwoX2xkIrZqjiQg1jTI=; b=UxSNtELP/KctQLvknOMJ1+RLheRIKAsMqeuMzsPGnNHZOkQlhZhuccp7kF1IQ4pBXE y5kfnrMAXMCt/nZw9DzPEgvAkoPmxmrjF+O/NQc64D0CahamIUAucqFk+BIJ+i1DAXan lz9+mfdjiaMTFtHqWUvhsJW2obb0oB7iAMGYK8luUbrr8F927b0EVY1En53yGR3gxXhJ RaDfMGVARLqWxMN5LsuSMkSyVc/xHS9OH1iql0sdq2hegd+015elbsSDOt4w8GebaOpr ITWTFtG/UducX4UVpZxOhHDurzf8sy/mcfPAZCc+VaN77UP55zNI0IKCR8roYM8GZ/LT wqQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760388088; x=1760992888; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=wCLtlY+GpSdapckAq80Uoda7FwoX2xkIrZqjiQg1jTI=; b=GMo4Zh6/IRI8nTyYUEgMD1Uc/8iXQrHnxk7oGpGElZQ3XNddCFx7Z8JmmQaKN7bKtA cUI42yVhuIB7C0o1+2elTW/ohyRUh6Jh+83bXr+nxcgzfUIfNlxAbwLLEZaMqWQspZ7G oUtligYvjEqUsSJcV8JM21y9na5Lf4GOY5n17a+KcYsxAihSDNXmQsn/OjEVgDRLIhe9 D0TV9BGB+e+mYEsueO6DCOxRzP6YYKKJkeX0ZqmDbjCFRmwO4r0af8y9hzE1Zxm/RbTU ZCLpnkOrKDwWtCIbb/wO9G281v7vEAM+cJEE4wYdXor0y2zlvC039AdbL8cl8wriKxnQ VyzA== X-Forwarded-Encrypted: i=1; AJvYcCWLSr193zqnviDTIxZw5sGx6Fw/36rYie3Pq0uxMItzppid6fk4WiaYqQoneVUh65nBCCeEpgybay3izt8=@vger.kernel.org X-Gm-Message-State: AOJu0Yw1rerDU2XD/L9mY4aK4h0mMqllx7p9oE3nBYUzjjHqS+xPcfB3 i2lSzUtFSdKXyybsEne4zayzCm14JciWBOCRqxB1gFdQVi4KKznA0Wl8 X-Gm-Gg: ASbGncvxXezuEhjWCSP8hjPlxW5+hGRATboROPx6JQ0EbeJ2cGHPlODMJfGRFmCpF+Y XAguHgIl2jcKhzkSOFnWHAieKJtuYx7PfTDBMOJuDs1YbeSln1mRwyZCSSGfsgT6m4Jx6TjAq4Z hdaYu/xQybkzq5TxG800vZnMiqN0sLpK5FB9basv5YOvifqwUWHAYWy3PpIsBcW1eTfHwBtMPfU k1/lcOpUVdhQL5El95TLOFclIAtop3pNcgOSN3JZrsFaAK0de6JEh5W8CECWYFr9v75LCSCyTPf 5HQO1tnpLZH2s3NM8Bhz3pjJZ7JVs3vkIJ3m5Px2izs8FbNgXmmU2Eyh/7uZMe4GdMkZFMlgfU3 ZmY3FfY1V0LEaYrOVq4vgjMt9Vk5hCQ== X-Google-Smtp-Source: AGHT+IFrDpANwGND6n4Bq/nSFTErKeDAVitiuC4/ag/cLsjoNuy/l3zpqrheKMdvIEEFGo6yIOFj0w== X-Received: by 2002:a17:907:7e88:b0:b3f:b7ca:26ca with SMTP id a640c23a62f3a-b50aaa96b30mr2242003166b.21.1760388087782; Mon, 13 Oct 2025 13:41:27 -0700 (PDT) Received: from krava ([176.74.159.170]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b55d8c12b9dsm1000097266b.45.2025.10.13.13.41.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Oct 2025 13:41:27 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 13 Oct 2025 22:41:19 +0200 To: Tao Chen Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, song@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH bpf-next RFC 0/2] Pass external callchain entry to get_perf_callchain Message-ID: References: <20251013174721.2681091-1-chen.dylane@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251013174721.2681091-1-chen.dylane@linux.dev> On Tue, Oct 14, 2025 at 01:47:19AM +0800, Tao Chen wrote: > Background > ========== > Alexei noted we should use preempt_disable to protect get_perf_callchain > in bpf stackmap. > https://lore.kernel.org/bpf/CAADnVQ+s8B7-fvR1TNO-bniSyKv57cH_ihRszmZV7pQDyV=VDQ@mail.gmail.com > > A previous patch was submitted to attempt fixing this issue. And Andrii > suggested teach get_perf_callchain to let us pass that buffer directly to > avoid that unnecessary copy. > https://lore.kernel.org/bpf/20250926153952.1661146-1-chen.dylane@linux.dev > > Proposed Solution > ================= > Add external perf_callchain_entry parameter for get_perf_callchain to > allow us to use external buffer from BPF side. The biggest advantage is > that it can reduce unnecessary copies. > > Todo > ==== > If the above changes are reasonable, it seems that get_callchain_entry_for_task > could also use an external perf_callchain_entry. > > But I'm not sure if this modification is appropriate. After all, the > implementation of get_callchain_entry in the perf subsystem seems much more > complex than directly using an external buffer. > > Comments and suggestions are always welcome. > > Tao Chen (2): > perf: Use extern perf_callchain_entry for get_perf_callchain > bpf: Pass external callchain entry to get_perf_callchain hi, I can't get this applied on bpf-next/master, what do I miss? thanks, jirka > > include/linux/perf_event.h | 5 +++-- > kernel/bpf/stackmap.c | 19 +++++++++++-------- > kernel/events/callchain.c | 18 ++++++++++++------ > kernel/events/core.c | 2 +- > 4 files changed, 27 insertions(+), 17 deletions(-) > > -- > 2.48.1 >