From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 C043C1531C5 for ; Wed, 26 Mar 2025 08:07:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742976475; cv=none; b=SF8ZLg3eUn5wKB5eFoDrbIgpoas8JgtZ+8+YoalIZoHwvELxxggTlOP1bM4GPU2mfFN9KCBWeEXW96jJ+9M4U/JyBhpp9OWiAJvQIkoOe+CHQg5euJznPcj5YiFlY3TNh9LnEV1vCDMq+xwHEWsjmROfBZi4GOfhTIm1RiBR7L0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742976475; c=relaxed/simple; bh=UxBS92GQ45LUnanF/bFoFizTZVD0tvd6G70vV86NyLg=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=Ntpj/KiVWu56hRv4TT9COdl2nrSPk/uTf3K8PzOl0JIQl7VJ5jUnm3tW2MipTOhZ8CxU3ZnypPJwuhzNBDlyEBhtAAeKj4gVMkdHfH3sV8+hndOmikyRUGDUw/Mhl7hwzfzuGLx8gki9xVm2/3Pdbvqv/SZFacAg3W4WFjxlLVc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=lNGrwlPF; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=q/6W+0Qe; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="lNGrwlPF"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="q/6W+0Qe" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1742976472; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ETk2UupwFvvVpDyiifSQD52EUhmJaQXXMm0OcMJCSE4=; b=lNGrwlPFgQZUCpVYeTMO1I7ez+L1MaaNktpucTkooQXGmpzCDqWbcshAM0lRUNVs/Vn72N JcLSjT+JdZs9c7zqZQTDElt8cLElb7FV71NAcnZO5GCWqSgtbv0Fr08OKDikxC3qCYjjYY PSmal4RSJzEXBoeEBfEIwyY3x2fDf9a9T+bjyF46VMkVMsjnn6RCV7AcrkVoxY7ljRkMQg K63kPxVwSgBhtOGJDWttBGcpbY06Cxvt5T/3FjY7garJ25USmLM9+6w1kzUrj+UbA+xJK5 fsi0Czd/bxReuM8NiWMozFBlMQtYmE4GJSP6YKvubjWL+KKA4S2qpRT19S2zbg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1742976472; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ETk2UupwFvvVpDyiifSQD52EUhmJaQXXMm0OcMJCSE4=; b=q/6W+0QeGFX1m3u5F50e3Wlrm25vjxKbCARTI72limhwint5vZ+C/xQ3gf4jGZAjJTWhQB FJrs6CrtG2KHCmBg== To: kernel test robot Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, Eric Dumazet , Benjamin Segall , Frederic Weisbecker , oliver.sang@intel.com Subject: Re: [tip:timers/core] [posix] 1535cb8028: stress-ng.epoll.ops_per_sec 36.2% regression In-Reply-To: <202503241406.5c9cb80a-lkp@intel.com> References: <202503241406.5c9cb80a-lkp@intel.com> Date: Wed, 26 Mar 2025 09:07:51 +0100 Message-ID: <87pli4z02w.ffs@tglx> Precedence: bulk X-Mailing-List: oe-lkp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, Mar 24 2025 at 14:39, kernel test robot wrote: > kernel test robot noticed a 36.2% regression of stress-ng.epoll.ops_per_sec on: > > commit: 1535cb80286e6fbc834f075039f85274538543c7 ("posix-timers: Improve hash table performance") > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git timers/core > > testcase: stress-ng > config: x86_64-rhel-9.4 > compiler: gcc-12 > test machine: 64 threads 2 sockets Intel(R) Xeon(R) Gold 6346 CPU @ 3.10GHz (Ice Lake) with 256G memory > parameters: > > nr_threads: 100% > testtime: 60s > test: epoll > cpufreq_governor: performance > > > In addition to that, the commit also has significant impact on the following tests: > > +------------------+---------------------------------------------------------------------------------+ > | testcase: change | stress-ng: stress-ng.epoll.ops_per_sec 124.9% improvement | > | test machine | 256 threads 2 sockets GENUINE INTEL(R) XEON(R) (Sierra Forest) with 128G memory | > | test parameters | cpufreq_governor=performance | > | | nr_threads=100% | > | | test=epoll | > | | testtime=60s | > +------------------+---------------------------------------------------------------------------------+ How on earth can this commit result in both a 36% regression and a 25% improvement with the same test? Unfortunately I can't reproduce any of it. I checked the epoll test source and it uses a posix timer, but that commit makes the hash less contended so there is zero explanation. Thanks, tglx