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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 69807C5AD5A for ; Wed, 12 Aug 2026 08:05:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=r/g+Wx9Hm2rhyYaTUofmlqgiLOYhMwW2+7a7AlyG+k4=; b=AnfYEgYnyBaF8TQ0k0NuQIkiIj IkRzQ1kT25RS9XtuKiCKqcsYmUfGXTp8PrBugm4Bgt7pvQQ+NifhfrywNkr/fzn0utHa7wAkhWSQY xY6U3SaYEqAfyK5uqm+TeNbWpNwW4VLUHWuzI++wF4TGl9fwnNPweLcH9ByzhzMgqXhAeQHbOkova o9inKO2FGQbUzhWi3AyDOZwpkxAlsISZ2svdZZvmEcCDKucKnZylRYdFgoSK1OEbjPAatYNMUA4Ul 5ngisPKS6PjGvC52KtpQASbPxccuUCSzjtn9MBxPnrRkIwdThekMgtMhHKsa+9qGgNmUICXN4kLsV Q4ZwDBvA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wu3yA-0000000FcKI-03O7; Wed, 12 Aug 2026 08:05:50 +0000 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wu3y7-0000000FcJj-2bxp for linux-nvme@lists.infradead.org; Wed, 12 Aug 2026 08:05:48 +0000 Received: from pps.filterd (m0353725.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 67C6360k1579898; Wed, 12 Aug 2026 08:05:43 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=r/g+Wx 9Hm2rhyYaTUofmlqgiLOYhMwW2+7a7AlyG+k4=; b=Nc3CoLTz5S7sVhMhkkru8G KXCWOMmt1WqRgO41x2Aws+baUh9y1I3Z+6XlGvZLrzd/91f129hByiYvUUk7/XDB vWdDXkXzXzZd8n9YLU+r6e2cr9w9yPw0AwndLkuA46gLGVhWQtBOvgE/74boILKN M8mbrgUy0vA6Pw9/h7ceEjpFMjFKWktArvsdJ73056Qov4eXn2Yc0zNGkbuVo3e6 Jm8i9zW9z9EXc518PHpG5hKe/ot8A4ZdSNNyHcfvEdF8Nn6911Jh3ZFN6IRcOKfH NmyJbkZnurXkY8xKKthcOQWaVHuGDEGLm72LvI3gGLjWZVQcuCq3PMPk/+D5Y4Xg == Received: from ppma23.wdc07v.mail.ibm.com (5d.69.3da9.ip4.static.sl-reverse.com [169.61.105.93]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4fyb23t1uy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Aug 2026 08:05:42 +0000 (GMT) Received: from pps.filterd (ppma23.wdc07v.mail.ibm.com [127.0.0.1]) by ppma23.wdc07v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 67C7uUeb027028; Wed, 12 Aug 2026 08:05:41 GMT Received: from smtprelay04.wdc07v.mail.ibm.com ([172.16.1.71]) by ppma23.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4fxg9h52dk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Aug 2026 08:05:41 +0000 (GMT) Received: from smtpav04.dal12v.mail.ibm.com (smtpav04.dal12v.mail.ibm.com [10.241.53.103]) by smtprelay04.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 67C85fqe40305382 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 12 Aug 2026 08:05:41 GMT Received: from smtpav04.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2033758052; Wed, 12 Aug 2026 08:05:41 +0000 (GMT) Received: from smtpav04.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 18B2D58056; Wed, 12 Aug 2026 08:05:37 +0000 (GMT) Received: from [9.61.0.237] (unknown [9.61.0.237]) by smtpav04.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 12 Aug 2026 08:05:36 +0000 (GMT) Message-ID: <1debeecf-672a-453d-b4d4-7f798045ae48@linux.ibm.com> Date: Wed, 12 Aug 2026 13:35:35 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 3/9] nvme-multipath: pass I/O type to nvme_find_path() To: John Garry , linux-nvme@lists.infradead.org Cc: hare@suse.de, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, dwagner@suse.de, kanie@linux.alibaba.com, jmeneghi@redhat.com, randyj@purestorage.com, martin.petersen@oracle.com, gjoyce@linux.ibm.com References: <20260809100825.2014133-1-nilay@linux.ibm.com> <20260809100825.2014133-4-nilay@linux.ibm.com> <70b23be2-0cb3-49fe-bff4-237082caaab3@oracle.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <70b23be2-0cb3-49fe-bff4-237082caaab3@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=XqfK/1F9 c=1 sm=1 tr=0 ts=6a7c2956 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=44NF9CiQjhv3s04OhcQA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEyMDA2MyBTYWx0ZWRfX8pZqEkRM/sMt j5HWgU+B1izZAhaCcxLB/n03euxKyxY6qtwQNrPG4YWXbtSbAtyqScf2bgIAx9oTXS2th+gDz9A ud1QjzsFoj+gbtjxSVEE6lfioWn8OExCbxhdA8yfJz6MsoCGi0uFVCM+S2m/J2vxBYhqO0Ms5aj i3C9B3jyaXD1cGWTm/eQ5NceWliMkGdOZHKDqOMvuFZBjgS4eiED9TYdaFGDwSS/5Mh5ikgF0px 8Yrn3BeSMpqQPxeywMRc8GDO7GofB3HPFk+re82+p9p75Z0qyzAw814TdQeQl9IP7J/Rtb83XQ7 7MXpJ3M1IXHLTUfcYtkqU9aLSsdixbxZOi4bAQ3cIdPr46IRIrK57TCLDLqab1SHUITJGpPHJ6b d5LJkZEszPSqP3ag7JuuWlE/fr/XV+qqzq2xC9JBAnEGB1qG9lSKr2HluzTB4aElGqLibcNer59 MCy8//grbn2dUMOwlkQ== X-Proofpoint-ORIG-GUID: _PJfUfAr9J7_k75z79YMbMK1fxrp9uAA X-Proofpoint-GUID: 0JrTMaORkFgQiiG0Q8UR--8JwyOhzKi8 X-Proofpoint-Spam-Info: AW1haW4tMjYwODEyMDA2MyBTYWx0ZWRfX99c8fhHAK+Kk d/hfzUUokhnKKNlOOu0cAZM21sTBUE2FA4Sw1V9TrIXQNB5UiZVSmDOFoDxHVn6zit/jA7DTPmo /8V9uKHXovMKnf9EXmZcDTp7N2SNe4s= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-12_02,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 adultscore=0 malwarescore=0 clxscore=1015 suspectscore=0 priorityscore=1501 impostorscore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608120063 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260812_010547_785925_F75B86B5 X-CRM114-Status: GOOD ( 22.53 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 8/11/26 4:06 PM, John Garry wrote: > On 10/08/2026 18:19, Nilay Shroff wrote: >>> It's a but unfortunate that we have to find op_type even for when not using the latency iopolicy. >>> >> I looked at a few alternatives to avoid passing op_type into >> nvme_find_path(), but couldn't find a cleaner approach. >> Fortunately, determining op_type is inexpensive, so I don't >> expect it to have any measurable performance impact. > > All I can think of is a variant of nvme_find_path() which accepts the bio, but that means more complication and code duplication - but not too much. > > As you mentioned, the processing should be small for this. > >> >>>>        if (likely(ns)) { >>>>            bio_set_dev(bio, ns->disk->part0); >>>>            /* >>>> @@ -572,7 +573,7 @@ static int nvme_ns_head_get_unique_id(struct gendisk *disk, u8 id[16], >>>>        int srcu_idx, ret = -EWOULDBLOCK; >>>>        srcu_idx = srcu_read_lock(&head->srcu); >>>> -    ns = nvme_find_path(head); >>>> +    ns = nvme_find_path(head, NVME_STAT_OTHER); >>>>        if (ns) >>>>            ret = nvme_ns_get_unique_id(ns, id, type); >>>>        srcu_read_unlock(&head->srcu, srcu_idx); >>>> @@ -588,7 +589,7 @@ static int nvme_ns_head_report_zones(struct gendisk *disk, sector_t sector, >>>>        int srcu_idx, ret = -EWOULDBLOCK; >>>>        srcu_idx = srcu_read_lock(&head->srcu); >>>> -    ns = nvme_find_path(head); >>>> +    ns = nvme_find_path(head, NVME_STAT_OTHER); >>>>        if (ns) >>>>            ret = nvme_ns_report_zones(ns, sector, nr_zones, args); >>>>        srcu_read_unlock(&head->srcu, srcu_idx); >>>> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h >>>> index 824651cc898d..8a9ec502912d 100644 >>>> --- a/drivers/nvme/host/nvme.h >>>> +++ b/drivers/nvme/host/nvme.h >>>> @@ -520,6 +520,13 @@ struct nvme_ns_ids { >>>>        u8    csi; >>>>    }; >>>> +enum nvme_stat_group { >>>> +    NVME_STAT_READ, >>>> +    NVME_STAT_WRITE, >>>> +    NVME_STAT_OTHER, >>> >>> Would NVME_STAT_OTHER ever be used in high frequency scenarios such that it is worth having its own type? If not, could NVME_STAT_READ be reused? >>> >> It may not be used in high-throughput scenarios, but treating these >> commands as READ or WRITE would unnecessarily skew the latency statistics >> for actual read/write workloads. Keeping them in a separate category >> avoids that distortion, so I think having NVME_STAT_OTHER makes sense. > > I can't imagine that NVME_STAT_OTHER could skew the READ/WRITE results too much, but I don't know the full range of IO for which NVME_STAT_OTHER would be used (so I may be wrong). > There're many opcodes which falls in other catogory here for instance, flush/write-zeros/compare/verify/dsm and few others... > BTW, it would be nice to mention the reason behind NVME_STAT_OTHER in the commit message. None of enum nvme_stat_group is described in much detail. > Yes make sense, I'd do the needful. Thanks, --Nilay