From owner-freebsd-arch@FreeBSD.ORG Wed Feb 19 19:59:39 2014 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7EEAD7ED; Wed, 19 Feb 2014 19:59:39 +0000 (UTC) Received: from mail-we0-x231.google.com (mail-we0-x231.google.com [IPv6:2a00:1450:400c:c03::231]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 9B3511D43; Wed, 19 Feb 2014 19:59:38 +0000 (UTC) Received: by mail-we0-f177.google.com with SMTP id t61so712668wes.8 for ; Wed, 19 Feb 2014 11:59:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=lFoxSb/Qa7RlBFsdnMBYmMBxHLL22X+hS5e7yNG2j40=; b=mAnh1BdvWm5m2B7ENLrsS+IdrlpgyG6b6sLvdX+Tp0hWOZJK3ML9UsFAoL5Pl+JRGo zggZmv2L3iHeHIah7ikI8dmDGGBK2NtOCyWOEQjkUt52ztfbHoz9EeHTCmqmiXZIq36t q6KP3vMJNeNFxoA7yMtNDVIoob1WPMBbIv1kzRrspKSmdCWcMSO9/SJkSNML4/fNpFUy LkrB5dE1zvqrNXWoiFzQ78rzqWYe+B3j5c61MR1/VdZr2vPAfZiIMSmRSZufiu3O7Tk/ bhjk/p3eK07wvcA+ozUYJJYAvrcHXCJofRjeftwhSqY3CZRjSvRdOho2Q67Dfa4CxoFw ydbA== X-Received: by 10.15.81.196 with SMTP id x44mr41590044eey.31.1392839976375; Wed, 19 Feb 2014 11:59:36 -0800 (PST) Received: from mavbook.mavhome.dp.ua ([134.249.139.101]) by mx.google.com with ESMTPSA id o45sm4513341eeb.18.2014.02.19.11.59.33 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 19 Feb 2014 11:59:35 -0800 (PST) Sender: Alexander Motin Message-ID: <53050D24.3020505@FreeBSD.org> Date: Wed, 19 Feb 2014 21:59:32 +0200 From: Alexander Motin User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Adrian Chadd Subject: Re: [rfc] bind per-cpu timeout threads to each CPU References: <530508B7.7060102@FreeBSD.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Jeffrey Faden , freebsd-current , "freebsd-arch@freebsd.org" X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Feb 2014 19:59:39 -0000 On 19.02.2014 21:51, Adrian Chadd wrote: > On 19 February 2014 11:40, Alexander Motin wrote: >> Clock interrupt threads, same as other ones are only softly bound to >> specific CPUs by scheduler preferring to run them on CPUs where they are >> scheduled. So far that was enough to balance load, but allowed threads to >> migrate, if needed. Is it too flexible for some use case? > > I saw it migrate under enough CPU load / pressure, right smack bang in > the middle of doing TCP processing. > > So if we're moving towards supporting (among others) a pcbgroup / RSS > hash style work load distribution across CPUs to minimise > per-connection lock contention, we really don't want the scheduler to > decide it can schedule things on other CPUs under enough pressure. > That'll just make things worse. True, though it is also not obvious that putting second thread on CPU run queue is better then executing it right now on another core. -- Alexander Motin