Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932259AbcJER6Z (ORCPT ); Wed, 5 Oct 2016 13:58:25 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:41010 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753846AbcJER6X (ORCPT ); Wed, 5 Oct 2016 13:58:23 -0400 Subject: Re: aio: questions with ioctx_alloc() and large num_possible_cpus() To: Benjamin LaHaise References: <20161005174146.GK23336@kvack.org> Cc: Kent Overstreet , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-kernel@vger.kernel.org From: Mauricio Faria de Oliveira Date: Wed, 5 Oct 2016 14:58:12 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20161005174146.GK23336@kvack.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16100517-0032-0000-0000-00000296B14B X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16100517-0033-0000-0000-00000F0A9B21 Message-Id: <737b5bf7-329e-c59d-7601-aea0f4ffbeab@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-10-05_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1610050302 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 681 Lines: 21 Hi Benjamin, On 10/05/2016 02:41 PM, Benjamin LaHaise wrote: > I'd suggest increasing the default limit by changing how it is calculated. > The current number came about 13 years ago when machines had orders of > magnitude less RAM than they do today. Thanks for the suggestion. Does the default also have implications other than memory usage? For example, concurrency/performance of as much aio contexts running, or if userspace could try to exploit some point with a larger number? Wondering about it because it can be set based on num_possible_cpus(), but that might be really large on high-end systems. Regards, -- Mauricio Faria de Oliveira IBM Linux Technology Center