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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 8 Jul 2019 10:09:41 +0100 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6899SVF29622532 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 8 Jul 2019 09:09:28 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1F17D42042; Mon, 8 Jul 2019 09:09:40 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3487B42045; Mon, 8 Jul 2019 09:09:39 +0000 (GMT) Received: from localhost.localdomain (unknown [9.124.35.94]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 8 Jul 2019 09:09:39 +0000 (GMT) Subject: Re: [RFC 0/2] Optimize the idle CPU search To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, vincent.guittot@linaro.org, subhra.mazumdar@oracle.com References: <20190708045432.18774-1-parth@linux.ibm.com> <20190708080836.GW3402@hirez.programming.kicks-ass.net> From: Parth Shah Date: Mon, 8 Jul 2019 14:39:38 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20190708080836.GW3402@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19070809-0028-0000-0000-00000381E4DF X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19070809-0029-0000-0000-00002441EC52 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-08_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=882 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907080120 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/8/19 1:38 PM, Peter Zijlstra wrote: > On Mon, Jul 08, 2019 at 10:24:30AM +0530, Parth Shah wrote: >> When searching for an idle_sibling, scheduler first iterates to search for >> an idle core and then for an idle CPU. By maintaining the idle CPU mask >> while iterating through idle cores, we can mark non-idle CPUs for which >> idle CPU search would not have to iterate through again. This is especially >> true in a moderately load system >> >> Optimize idle CPUs search by marking already found non idle CPUs during >> idle core search. This reduces iteration count when searching for idle >> CPUs, resulting in lower iteration count. > > Have you seen these patches: > > https://lkml.kernel.org/r/20180530142236.667774973@infradead.org > > I've meant to get back to that, but never quite had the time :/ > Ok, I was not aware of this patch-set. It seems interesting and I will evaluate it. Thanks