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 A72B0C433F5 for ; Thu, 16 Dec 2021 15:48:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238676AbhLPPsG (ORCPT ); Thu, 16 Dec 2021 10:48:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238697AbhLPPsD (ORCPT ); Thu, 16 Dec 2021 10:48:03 -0500 Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EFB4C061574 for ; Thu, 16 Dec 2021 07:48:03 -0800 (PST) Received: by mail-io1-xd31.google.com with SMTP id c3so35760172iob.6 for ; Thu, 16 Dec 2021 07:48:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=NRFQR8Yf1vYbRc7EqH9E5i9XTaBo5dlhI5KykDhEunY=; b=jbGPcR8DsNLJmTTf6Jn9+BAvg4fll+eALhhOgFsGp/QxKiyf2eXeO/QZehs90taEM5 3LtUg4rDb794xYffxF2sADQi7iP+XEXA1KB3sonsG0AHRXtK2neRkUFAPylYDlYVYqU5 or8HEX0QhTXCjKXZgwdfg1t97UiAHTeGGtfIQHInHTzRBpmwh3SfhXau2MrLoplwy24r W8r16JxcPaTWD95IJF9JIUZSnEd3+Eme0MfTGZyOX/qUogC7yPIKavUJmqWVExMS3HBY CxNpYVcHQsZrcJJItYMK2+tx3ivpnbOecMDV82BSlSTgaMG8ydKudoBBFSB8X4vGeS3j weGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=NRFQR8Yf1vYbRc7EqH9E5i9XTaBo5dlhI5KykDhEunY=; b=hFpA93ItwsqWKQsU5rSx0fa13K7bjIQ5CDa5yyJejWUIYK3IyvC0/15G8fYpRLa4/V twNBkBlWDGqqHt3uxyBQgigbbSBQMgeyUaB/7BDlX7TRNbE35jTPMJRoLvSAMl38801o Vip/cKCBBTolGBMStnKFTZlKCddWZXra3hDsCLpT1+0ZFN9D0RyLeYAqbNp4YsRI7Bcn cjSiqCAszfFxtu9lLtInxZY8ElIJIVcxg1bAI51dtnPlTGF6kn2SLJdlZyBUT7sd6Tjy 2ENxTzYMIvBfSWiy2/k/KcV97Rw4WL/IEjvnYSIQhHFZ6fkYo+zueyvcgZkyyh/ryFpY UOpA== X-Gm-Message-State: AOAM533+BMKQb9XZBRRZdTUwUvcay0QUzXzw/bOHyuNJxSahX8QEJ/KS 3rYn8kHzrUpdRGnZT/aD7ZwX35iC+wZpYw== X-Google-Smtp-Source: ABdhPJwOvcVk5qmGsJ1rKQqPyPcBkxxJ2k5pa75zQElP9O9KZv4qyx8PvMI6zG+010jN7cnOKI0L4w== X-Received: by 2002:a02:85a9:: with SMTP id d38mr9988551jai.71.1639669682314; Thu, 16 Dec 2021 07:48:02 -0800 (PST) Received: from [192.168.1.30] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id j7sm3552824iow.26.2021.12.16.07.48.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Dec 2021 07:48:02 -0800 (PST) Subject: Re: [PATCH 4/4] nvme: add support for mq_ops->queue_rqs() To: Max Gurtovoy , Christoph Hellwig Cc: io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, Hannes Reinecke References: <20211215162421.14896-1-axboe@kernel.dk> <20211215162421.14896-5-axboe@kernel.dk> <2adafc43-3860-d9f0-9cb5-ca3bf9a27109@nvidia.com> From: Jens Axboe Message-ID: <06ab52e6-47b7-6010-524c-45bb73fbfabc@kernel.dk> Date: Thu, 16 Dec 2021 08:48:00 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <2adafc43-3860-d9f0-9cb5-ca3bf9a27109@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 12/16/21 6:06 AM, Max Gurtovoy wrote: > > On 12/16/2021 11:08 AM, Christoph Hellwig wrote: >> On Wed, Dec 15, 2021 at 09:24:21AM -0700, Jens Axboe wrote: >>> + spin_lock(&nvmeq->sq_lock); >>> + while (!rq_list_empty(*rqlist)) { >>> + struct request *req = rq_list_pop(rqlist); >>> + struct nvme_iod *iod = blk_mq_rq_to_pdu(req); >>> + >>> + memcpy(nvmeq->sq_cmds + (nvmeq->sq_tail << nvmeq->sqes), >>> + absolute_pointer(&iod->cmd), sizeof(iod->cmd)); >>> + if (++nvmeq->sq_tail == nvmeq->q_depth) >>> + nvmeq->sq_tail = 0; >> So this doesn't even use the new helper added in patch 2? I think this >> should call nvme_sq_copy_cmd(). > > I also noticed that. > > So need to decide if to open code it or use the helper function. > > Inline helper sounds reasonable if you have 3 places that will use it. Yes agree, that's been my stance too :-) >> The rest looks identical to the incremental patch I posted, so I guess >> the performance degration measured on the first try was a measurement >> error? > > giving 1 dbr for a batch of N commands sounds good idea. Also for RDMA host. > > But how do you moderate it ? what is the batch_sz <--> time_to_wait > algorithm ? The batching is naturally limited at BLK_MAX_REQUEST_COUNT, which is 32 in total. I do agree that if we ever made it much larger, then we might want to cap it differently. But 32 seems like a pretty reasonable number to get enough gain from the batching done in various areas, while still not making it so large that we have a potential latency issue. That batch count is already used consistently for other items too (like tag allocation), so it's not specific to just this one case. -- Jens Axboe