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 879AFC3A59F for ; Sat, 26 Nov 2022 06:09:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230011AbiKZGJE (ORCPT ); Sat, 26 Nov 2022 01:09:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230114AbiKZGJB (ORCPT ); Sat, 26 Nov 2022 01:09:01 -0500 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D53F205E5; Fri, 25 Nov 2022 22:08:59 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4NK1Wp0gVcz4f3kpS; Sat, 26 Nov 2022 14:08:54 +0800 (CST) Received: from [10.174.176.73] (unknown [10.174.176.73]) by APP4 (Coremail) with SMTP id gCh0CgB3m9h4rYFj1lyxBA--.33831S3; Sat, 26 Nov 2022 14:08:57 +0800 (CST) Subject: Re: Why is MEGASAS_SAS_QD set to 256? To: Yu Kuai , Ming Lei Cc: John Garry , kashyap.desai@broadcom.com, sumit.saxena@broadcom.com, shivasharan.srikanteshwara@broadcom.com, jejb@linux.ibm.com, martin.petersen@oracle.com, megaraidlinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block , "zhangyi (F)" , "yukuai (C)" References: <1c4d66ca-fe1a-3d1a-d7f9-4981d2fc9eb1@huaweicloud.com> <2b89210a-222c-a919-ab5b-c76830308f92@huaweicloud.com> From: Yu Kuai Message-ID: <7fa1cf9f-3cd3-9ca8-8ddc-0c8407a466e8@huaweicloud.com> Date: Sat, 26 Nov 2022 14:08:56 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: gCh0CgB3m9h4rYFj1lyxBA--.33831S3 X-Coremail-Antispam: 1UD129KBjvdXoW7Wr4DJrWUZrykZry5Wr4DJwb_yoWfGFXEgw 4jkFn7Gw15Grs2qa1UJry5ArZ3GFZ3tasxA34qq3W5X39rC3W3KrW5Zw1rZan3Grsxtrn7 tr4Yg3WYqws09jkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUb3xFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k26cxKx2IYs7xG 6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8w A2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j 6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcVAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kI c2xKxwCYjI0SjxkI62AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4 AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE 17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMI IF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Gr0_Zr1l IxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvf C2KfnxnUUI43ZEXa7VU1a9aPUUUUU== X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/11/26 14:08, Yu Kuai 写道: > Hi, Ming > > 在 2022/11/26 10:18, Ming Lei 写道: >> >> If you want aggressive merge on sequential IO workload, the queue >> depth need >> to be a bit less, then more requests can be staggered into scheduler >> queue, >> and merge chance is increased. > > But if nr_requests >= queue_depth, it seems to me elevator will have no > effect, no request can be merged or sorted by scheduler, right? Sorry that should be nr_requests <= queue_depth. >> >> If you want good perf on random IO perf, the queue depth needs to >> be deep enough to have enough parallelism for saturating SSD internal. >> >> But we don't recognize sequential/random IO pattern, and usually fixed >> queue depth is used. > > Is it possible to use none elevator and set large queue_depth if nvme is > used in this case? > > Thansk, > Kuai >> >> Thanks, >> Ming >> >> . >> > > . >