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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 935C0C4338F for ; Sat, 31 Jul 2021 17:15:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74C4960EB7 for ; Sat, 31 Jul 2021 17:15:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231189AbhGaRP0 (ORCPT ); Sat, 31 Jul 2021 13:15:26 -0400 Received: from mail-pj1-f47.google.com ([209.85.216.47]:55137 "EHLO mail-pj1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229840AbhGaRPY (ORCPT ); Sat, 31 Jul 2021 13:15:24 -0400 Received: by mail-pj1-f47.google.com with SMTP id b6so19658292pji.4; Sat, 31 Jul 2021 10:15:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=DlaoNmwnEWDtxTjH4uaBlzq3ZGun3yheeOVe4kPMWlc=; b=nRiNHjZ3ak47qCrpNaQC0KlEFsD2IJqBqsI1jy+9CnSM9OelaAgyA+Mu1MpcgIs33K MjTuU01NGmSM3JZkodBKzlqvY7euttqBs+vUI/X4Wky9Z4F5YoY/FY9v+1T4wJk1wMqp uyuR9peYgOq5CdJwj6JuMSN2wtPUeborC3fpNiF+BO/p+RdsZo4jqLIkjf2H9wv2yWcd 0aPU4N2NJQndTWUwMJdKLmtguitLd5aDvvCQLx+gJlN1PRM1mgCF+AT64aqjPlPBFy7l 30fA1O9pqE8ytkwTagftLoWxnF4Nk5dfidjo4DqJUZjkvfDminEzRO9X7AhsKeS2wCQ8 oB8g== X-Gm-Message-State: AOAM530AyiOT1ba5ld2GHS9chB2nRk5whiy6MnnsWZBk98rF/EJPNoi9 UbnSAvSw+/rL2sLUcI8XPBI= X-Google-Smtp-Source: ABdhPJxagnFWjqey40tjfYyQ5SyxoZzmV1olLTHdeYhT7HZM2cviRdp277uKthSeil31eA/NJXkRIQ== X-Received: by 2002:a17:90a:d90f:: with SMTP id c15mr9207955pjv.178.1627751717376; Sat, 31 Jul 2021 10:15:17 -0700 (PDT) Received: from ?IPv6:2601:647:4000:d7:13bf:959e:93b8:7d56? ([2601:647:4000:d7:13bf:959e:93b8:7d56]) by smtp.gmail.com with ESMTPSA id z5sm2501918pff.97.2021.07.31.10.15.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 31 Jul 2021 10:15:16 -0700 (PDT) Subject: Re: [PATCH] blk-mq: allow hardware queue to get more tag while sharing a tag set To: Yu Kuai , axboe@kernel.dk, ming.lei@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com References: <20210712031818.31918-1-yukuai3@huawei.com> From: Bart Van Assche Message-ID: Date: Sat, 31 Jul 2021 10:15:14 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210712031818.31918-1-yukuai3@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/11/21 8:18 PM, Yu Kuai wrote: > If there are multiple active queues while sharing a tag set, it's not > necessary to limit the available tags as same share for each active queue > if no one ever failed to get driver tag. And fall back to same share if > someone do failed to get driver tag. > > This modification will be beneficial if total queue_depth of disks > on the same host is less than total tags. This patch adds new atomic operations in the hot path and hence probably has a negative performance impact. What is the performance impact of this patch for e.g. null_blk when submitting I/O from all CPU cores? Thanks, Bart.