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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F392CC004C0 for ; Fri, 20 Oct 2023 20:46:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233175AbjJTUqK (ORCPT ); Fri, 20 Oct 2023 16:46:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232791AbjJTUpu (ORCPT ); Fri, 20 Oct 2023 16:45:50 -0400 Received: from mail-pg1-f172.google.com (mail-pg1-f172.google.com [209.85.215.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EBA9B172E; Fri, 20 Oct 2023 13:45:42 -0700 (PDT) Received: by mail-pg1-f172.google.com with SMTP id 41be03b00d2f7-5a9bc2ec556so897590a12.0; Fri, 20 Oct 2023 13:45:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697834742; x=1698439542; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Vutrsb5JnCQsKaXFvh73rRJHAgEusiSsuInphwVkJa4=; b=SNnyYSdeoWe+upBQ1AdNgtA3pwSinRXfR8V8pEp8pDbXL36MLAMY0b9XqgJS9ISRmw XyTG+JqeC7tbbaI14RmDWpVVGJaY+xXrXWcCL+YaG/dp/6we4U+LphH6q64qGREDKXxS Igo7CBHqFr4GiYe6isfxay0smdXP4+kKwh69RtQ7JSCntchpKLxgnMxUyVeOGSDpcE1v y4AIz9vmxfTzAhDlQEWdtFRWgebSp3DCF3llV/yrm2f6916cssjzP28Ds1X3VAkrTHOt 3G7v/xEMfz3x5EKfa/DK2EBqPDEQ4tPBS8STLuwIQZhRSovWZKLfGZh0oNTtUkqCcFtH /u9Q== X-Gm-Message-State: AOJu0YwYg0jRqvJ/o1LvVuabSH4gFv6GaXDDXIHlMDeMdYfM6B6flY1W wI31kquLHLnFTgXsH0iqtCo= X-Google-Smtp-Source: AGHT+IHcoxyaOXOn8IwRdHquaMtX3ArdAIWiXujrLn6NFN7C5QoFgHXgr8GegShqNs5oO3F0PpFnDw== X-Received: by 2002:a05:6a20:7d96:b0:13a:e955:d958 with SMTP id v22-20020a056a207d9600b0013ae955d958mr3258701pzj.7.1697834742070; Fri, 20 Oct 2023 13:45:42 -0700 (PDT) Received: from ?IPV6:2620:15c:211:201:72ba:c99b:d191:901c? ([2620:15c:211:201:72ba:c99b:d191:901c]) by smtp.gmail.com with ESMTPSA id a6-20020aa78e86000000b0068fd026b496sm1968205pfr.46.2023.10.20.13.45.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Oct 2023 13:45:41 -0700 (PDT) Message-ID: <42639844-8758-4396-bb2c-ffcc8593d205@acm.org> Date: Fri, 20 Oct 2023 13:45:40 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 00/14] Pass data temperature information to SCSI disk devices Content-Language: en-US To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , Niklas Cassel , Avri Altman , Bean Huo , Daejun Park References: <20231017204739.3409052-1-bvanassche@acm.org> <3f3c2289-3185-4895-92cb-0692e3ca9ebc@kernel.dk> From: Bart Van Assche In-Reply-To: <3f3c2289-3185-4895-92cb-0692e3ca9ebc@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 10/18/23 12:09, Jens Axboe wrote: > I'm also really against growing struct bio just for this. Why is patch 2 > not just using the ioprio field at least? Hi Jens, Can you please clarify whether your concern is about the size of struct bio only or also about the runtime impact of the comparisons that have been added in attempt_merge() and blk_rq_merge_ok()? It may be possible to eliminate the overhead of the new comparisons as follows: * Introduce a union of struct { I/O priority; data lifetime; } and u32. * Use that union in struct bio instead of bi_ioprio and bi_lifetime. * Use that union in struct request instead of the ioprio and lifetime members. * In attempt_merge() and blk_rq_merge_ok(), compare the u32 union member instead of comparing the I/O priority and data lifetime separately. Thanks, Bart.