From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 EF3614A3E for ; Sat, 28 Mar 2026 01:21:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774660913; cv=none; b=h9GuVANJM2CSrxNvlAk1Tg6Z4GX+EcdqFlu23KpYs4nw62Bsl0BMyjHnm+zx+5QVeBqTbBnSHl/mwFGOKtTyXww/0m1n5ikAAxZR1QJ0GQFMB77ZHvkVBmVrMFVFWYBcSMXkX8HkhX2WjAsBZoNkXXHwxUxdGeQNcvrfW8YKxdQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774660913; c=relaxed/simple; bh=w25jMyvivRJ21SmF812an6mvD23Z9r3qEdpX+YDSiBA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CS5i1L8JPrNS9gH1xsJCPT5IOXftGBO0IZb9uPMLBJ2fvDBf8IVtMO1Rx7Ms4HktAGBMpotjZP6Z/EWI64Fzym0TnrvvJQDM93/etRyejqJtXjlyuzESqVWBrlCm4esInCbmKoxP6MOLTeKZ/V7MLEy4VIDxJSmCabdRzpmM8R4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=HUJL7wii; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="HUJL7wii" Received: from [172.27.2.41] (c-76-133-66-138.hsd1.ca.comcast.net [76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 62S1Kbjm300586 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 27 Mar 2026 18:20:37 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 62S1Kbjm300586 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2026032601; t=1774660840; bh=LpJgNDkdb9xBldylxc6E4Sin+9DvQCWl2yE7lArCLto=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=HUJL7wiis0bBi+8Bsgk4/i9ddqWVVa5XRwVyPMvo5ZVk5IK7VNoV/IPIPyTi2DgJ8 zfU6CbdRg9cfjLisTdpSrt2YgXWICRyPZFajJrDtvLxobqTzG1oW91WGjbMuNCYaag 5hU/hTnVjXCUcWu4MLGruEA0vytTVbdq5dc+4KvkrSWqi/7TMy2T3fRBCPtaJ3yRaf 35kYobQxpTMMNtST2uYP1dxVy9yzAwmbDBDCxVYMhjkozbIE/1IWV/JIqUMg9s145x nVJkShWzpTjKcAaQEIm3QinRV0HhkxwggK5jRMMWHjzih0iffVuKmSr5sbX2a0x10w 6p2EtHIdPeQow== Message-ID: <80be63da-360b-41f5-a45f-81335f8af1c2@zytor.com> Date: Fri, 27 Mar 2026 18:20:32 -0700 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: [PATCH v2 0/3] x86/fred: enable FRED by default To: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , the arch/x86 maintainers Cc: "Peter Zijlstra (Intel)" , Kees Cook , Xin Li , "Ahmed S. Darwish" , Sohil Mehta , Linux Kernel Mailing List , Jens Axboe References: <20260325230151.1898287-1-hpa@zytor.com> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2026-03-26 15:11, Andy Lutomirski wrote: > > Those performance increases while with fio / io_uring are ridiculous. I wonder whether anyone can looked at /proc/interrupts to try to figure out what's going on. I imagine we're bottlenecking on IO interrupts or something and FRED speeds that up by a factor of several, but this makes me wonder whether there's some tuning that should be done. > > Jens, for background, FRED ought to speed up page faults and interrupts (both IPI and device) by a considerable amount -- maybe a reduction of 20k or more cycles per interrupt. But Phoronix is showing up to a factor of 2 (!) actual performance increase using io_uring with a job count of 8. Now maybe 8 is too small, but I'm wondering whether the io_uring or IO part is missing some optimization that it ought to have. > Hi Andy! Long time no C! Either way, I presume neither of you have any problems with the patchset itself? -hpa