From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C67CBC433DB for ; Wed, 24 Feb 2021 03:07:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A9E564DFF for ; Wed, 24 Feb 2021 03:07:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230442AbhBXDHf (ORCPT ); Tue, 23 Feb 2021 22:07:35 -0500 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:37304 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229961AbhBXDHe (ORCPT ); Tue, 23 Feb 2021 22:07:34 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R431e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UPPcA2a_1614136011; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UPPcA2a_1614136011) by smtp.aliyun-inc.com(127.0.0.1); Wed, 24 Feb 2021 11:06:51 +0800 Subject: Re: [PATCH v2 1/1] io_uring: allocate memory for overflowed CQEs To: Pavel Begunkov , Jens Axboe , io-uring@vger.kernel.org References: From: Hao Xu Message-ID: Date: Wed, 24 Feb 2021 11:06:51 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org ÔÚ 2021/2/23 ÏÂÎç8:40, Pavel Begunkov дµÀ: > Instead of using a request itself for overflowed CQE stashing, allocate > a separate entry. The disadvantage is that the allocation may fail and > it will be accounted as lost (see rings->cq_overflow), so we lose > reliability in case of memory pressure. However, it opens a way for for > multiple CQEs per an SQE and even generating SQE-less CQEs > > Signed-off-by: Pavel Begunkov > --- Hi Pavel, Allow me to ask a stupid question, why do we need to support multiple CQEs per SQE or even SQE-less CQEs in the future? Thanks, Hao