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([2600:380:9b5a:c5dd:b564:550c:8958:e9dc]) by smtp.gmail.com with ESMTPSA id y6-20020a4ab406000000b0059a9652eee4sm814630oon.25.2024.02.03.04.11.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 03 Feb 2024 04:11:49 -0800 (PST) Message-ID: Date: Sat, 3 Feb 2024 05:11:47 -0700 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/26] Zone write plugging Content-Language: en-US To: Damien Le Moal , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, "Martin K . Petersen" , dm-devel@lists.linux.dev, Mike Snitzer Cc: Christoph Hellwig References: <20240202073104.2418230-1-dlemoal@kernel.org> <147de7c4-7050-4b1d-a48c-c0316a81baee@kernel.org> From: Jens Axboe In-Reply-To: <147de7c4-7050-4b1d-a48c-c0316a81baee@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/2/24 12:37 AM, Damien Le Moal wrote: > On 2/2/24 16:30, Damien Le Moal wrote: >> The patch series introduces zone write plugging (ZWP) as the new >> mechanism to control the ordering of writes to zoned block devices. >> ZWP replaces zone write locking (ZWL) which is implemented only by >> mq-deadline today. ZWP also allows emulating zone append operations >> using regular writes for zoned devices that do not natively support this >> operation (e.g. SMR HDDs). This patch series removes the scsi disk >> driver and device mapper zone append emulation to use ZWP emulation. >> >> Unlike ZWL which operates on requests, ZWP operates on BIOs. A zone >> write plug is simply a BIO list that is atomically manipulated using a >> spinlock and a kblockd submission work. A write BIO to a zone is >> "plugged" to delay its execution if a write BIO for the same zone was >> already issued, that is, if a write request for the same zone is being >> executed. The next plugged BIO is unplugged and issued once the write >> request completes. >> >> This mechanism allows to: >> - Untangle zone write ordering from the block IO schedulers. This >> allows removing the restriction on using only mq-deadline for zoned >> block devices. Any block IO scheduler, including "none" can be used. >> - Zone write plugging operates on BIOs instead of requests. Plugged >> BIOs waiting for execution thus do not hold scheduling tags and thus >> do not prevent other BIOs from being submitted to the device (reads >> or writes to other zones). Depending on the workload, this can >> significantly improve the device use and the performance. >> - Both blk-mq (request) based zoned devices and BIO-based devices (e.g. >> device mapper) can use ZWP. It is mandatory for the >> former but optional for the latter: BIO-based driver can use zone >> write plugging to implement write ordering guarantees, or the drivers >> can implement their own if needed. >> - The code is less invasive in the block layer and in device drivers. >> ZWP implementation is mostly limited to blk-zoned.c, with some small >> changes in blk-mq.c, blk-merge.c and bio.c. >> >> Performance evaluation results are shown below. >> >> The series is organized as follows: > > I forgot to mention that the patches are against Jens block/for-next > branch with the addition of Christoph's "clean up blk_mq_submit_bio" > patches [1] and my patch "null_blk: Always split BIOs to respect queue > limits" [2]. I figured that was the case, I'll get both of these properly setup in a for-6.9/block branch, just wanted -rc3 to get cut first. JFYI that they are coming tomorrow. -- Jens Axboe