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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A6329C43215 for ; Wed, 20 Nov 2019 21:58:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 742B420672 for ; Wed, 20 Nov 2019 21:58:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="QtCd1255" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725854AbfKTV6o (ORCPT ); Wed, 20 Nov 2019 16:58:44 -0500 Received: from mail-wr1-f67.google.com ([209.85.221.67]:46876 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725819AbfKTV6n (ORCPT ); Wed, 20 Nov 2019 16:58:43 -0500 Received: by mail-wr1-f67.google.com with SMTP id b3so1765813wrs.13 for ; Wed, 20 Nov 2019 13:58:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=from:mime-version:thread-index:date:message-id:subject:to:cc; bh=p8LCe9JWGcvpS2ewyZOiDIpe5TyhQwLY0HM6jhprWQw=; b=QtCd1255MUFcdBLBBfNmjNjzGPGgAfsCixZsPaR4oYW+L0msGLFHRvtAlW4HuEU8mO GJWCZfSIztiQNh94q5zlOaOQEjSHj/D9W3RVY9znxUBSlQKjHgFxCGMiQPyz9Z9kozhU X4Me1HPZ64r285gtMVmbHufCRm11UFI1X2LEQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:mime-version:thread-index:date:message-id :subject:to:cc; bh=p8LCe9JWGcvpS2ewyZOiDIpe5TyhQwLY0HM6jhprWQw=; b=SNSqATzrNSONA4G06GJjEhld4xMRuJ4c3Ir3vMorYc8ub3F7fpIg4C/ECP/7bKcFjY N7HijvnUmP7v/psvet1JiPDg/RPd0I98dRK1cmzmOv8JQShtXDWigYFwzV794Nyc+sn/ 6kFP1Io/xftg/kX5X6j9344bEzaDG0K11FTGngFBQx0DUXe0fcKAYrCbHxs4Uye2YcU/ ss0I46O4mktSOib8IxhWxgypi1vIBi090FxWQS3mSJ1S96bWuDsnp/YsVHlHALgR2NzQ 9pXhtUfkpL+1/vluS8uzaJah6AzeYx+ANq163NWG3mR0NyC9pOnlAlau0NWbfWSeh2o/ Mbrw== X-Gm-Message-State: APjAAAVh1Dwewy/l79aB4lCZnioQI++Nu+EqZIRiwbyjPEi/r0RiHfOZ gVhvp2JDNTqTPMKcRMoWGSEJy0GXDO3UoxcWvFjNEg== X-Google-Smtp-Source: APXvYqzSWKnd2Ge6i6FzlvK3By3OqKebKKjL+WI9yB2uVL4o+4QIYjH2ELHEzEHQfn14hxHtyyXdJ7+SdO+YwZ8AR/w= X-Received: by 2002:adf:eecc:: with SMTP id a12mr6143155wrp.363.1574287121644; Wed, 20 Nov 2019 13:58:41 -0800 (PST) From: Sumanesh Samanta MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AdWf7SRsTAXNfNyfSv6Y9At6URzH3g== Date: Wed, 20 Nov 2019 14:58:40 -0700 Message-ID: Subject: Re: [PATCH 4/4] scsi: core: don't limit per-LUN queue depth for SSD To: emilne@redhat.com Cc: axboe@kernel.dk, bart.vanassche@wdc.com, hare@suse.de, hch@lst.de, jejb@linux.ibm.com, kashyap.desai@broadcom.com, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, martin.petersen@oracle.com, ming.lei@redhat.com, sathya.prakash@broadcom.com, shivasharan.srikanteshwara@broadcom.com, suganath-prabu.subramani@broadcom.com, sumit.saxena@broadcom.com Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org >Ordinarily I'd prefer a host template attribute as Sumanesh proposed, >but I dislike wrapping the examination of that and the queue flag in >a macro that makes it not obvious how the behavior is affected. I think we can have a host template attribute and discard this check altogether, that is not check device_busy for both SDD and HDDs. As both you and Hannes mentioned, this change affects high end controllers most, and most of them have some storage IO size limit. Also, for HDD sequential IO is almost always large and touch the controller max IO size limit. Thus, I am not sure merge matters for these kind of controllers. Database use REDO log and small sequential IO, but those are targeted to SSDs, where latency and IOPs are far more important than IO merging. If this patch is opt-in for drivers, so any LLD that cannot take advantage of the flag need not set it, and would work as-is Thanks, Sumanesh