From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from anarch128.org (anarch128.org [23.253.174.110]) (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 303A01514DF for ; Wed, 3 Apr 2024 21:09:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=23.253.174.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712178559; cv=none; b=H0hjb9dTAFsA3SpMxo+7AG/2cioI51HYbhrju88UQ9rHMpBUJbbHQH61e3RhvXqqUIIYHPYWBYrozcZWuDB3PAtIjm81E4tKstYWhdrvJScRNaLD4/vmE76uqz6elVduEfJLETL820ntm331u4uGVh51ZXk6oOSULkyvnTn51rs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712178559; c=relaxed/simple; bh=nuAESWLU4gI8q+WylOWnOVd3iZvUzYqUM2as5Y3TWqg=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=ho5nulCx6fJjdbSQZaBp88UknhkdIPTGSTKZPn9Ooa2OGCV3Z50hK/Jds0046n8LwacdT9bbe7jmispFdM5PJFMJnOB7/lBMm+rjwKrfwfk0wjl+gBA+6AVmuJCFdljM670CnWyLvIsLB3+2bVvOhdQOX/aZmpRKRO00ZWFHDgI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=metaparadigm.com; spf=pass smtp.mailfrom=metaparadigm.com; dkim=fail (2048-bit key) header.d=metaparadigm.com header.i=@metaparadigm.com header.b=r6MMeVXJ reason="signature verification failed"; arc=none smtp.client-ip=23.253.174.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=metaparadigm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=metaparadigm.com Authentication-Results: smtp.subspace.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=metaparadigm.com header.i=@metaparadigm.com header.b="r6MMeVXJ" Received: from [192.168.1.5] (default-rdns.vocus.co.nz [202.150.110.104] (may be forged)) (authenticated bits=0) by anarch128.org (8.15.2/8.15.2/Debian-22) with ESMTPSA id 433L2FEa382974 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Wed, 3 Apr 2024 21:02:18 GMT Authentication-Results: anarch128.org; auth=pass; dkim=pass (2048-bit rsa key sha256) header.d=metaparadigm.com header.i=@metaparadigm.com header.b=r6MMeVXJ header.a=rsa-sha256 header.s=100043; x-return-mx=pass header.domain=metaparadigm.com policy.is_org=yes (MX Records found: mail.anarch128.org); x-return-mx=pass smtp.domain=metaparadigm.com policy.is_org=yes (MX Records found: mail.anarch128.org) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=metaparadigm.com; s=100043; t=1712178140; bh=nuAESWLU4gI8q+WylOWnOVd3iZvUzYqUM2as5Y3TWqg=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=r6MMeVXJrYh8TU6IvNXWfAJ/jeI0p8AzI0MBiYN24S55BTnH0aE/+ZT6ACEtW6ba6 R8FacpREBQ+MEzthYU4wcIR0PPlVJvctyB0rnvPi4XAJfbJ37GMdNQUneRBVjzlZaK OoE24hC9Sn2gITNZGv08DXa92LBdEgUSHCA6FDlxYO1712DdMHjVpuHVrtwVFUr5y+ go3+N0FKNjhQ0Za5Nf64eqTy4ZaBAEOtXk7yNe3gbEn+5qiBtuEvC4KvW2VRQItHQT 8sl8fh8XBORNtfjxHl4RaJxjzDU5nGiZOgnZx5HIq9fN2C++110U+HcW4yT12HMMqb /si3w31lC/Zww== Message-ID: <422feb1a-4b4e-45b6-838a-78e394dec9cc@metaparadigm.com> Date: Thu, 4 Apr 2024 10:02:10 +1300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: user-space concurrent pipe buffer scheduler interactions From: Michael Clark To: Linus Torvalds Cc: Jens Axboe , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org References: <969ccc0f-d909-4b45-908e-e98279777733@metaparadigm.com> <1a116a43-fd2e-4f03-8a17-75816fc62717@metaparadigm.com> Content-Language: en-US Organization: Metaparadigm In-Reply-To: <1a116a43-fd2e-4f03-8a17-75816fc62717@metaparadigm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/4/24 09:39, Michael Clark wrote: > So maybe it is possible to look at how many LOCK instructions were > retired in the last scheduler quantum ideally with retired-success, > retired-failed for interlocked-compare-and-swap. Maybe it is just a > performance counter and doesn't require perf tracing switched on? just occurred to me that you could stash the address and width of the last failed interlocked-compare-and-swap to deduce wait-on-address or even ask the processor in some circumstances to generate a precise interrupt so that you could reschedule it. an idle thought. like if it is going to fail we might as well jump straight to the scheduler.