From: Keith Busch <kbusch@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
Ming Lei <ming.lei@redhat.com>,
Damien Le Moal <damien.lemoal@opensource.wdc.com>,
Ed Tsai <ed.tsai@mediatek.com>
Subject: Re: [PATCH v2] block: Improve shared tag set performance
Date: Wed, 18 Jan 2023 15:14:14 -0700 [thread overview]
Message-ID: <Y8hvNmyR3U1ge3H3@kbusch-mbp> (raw)
In-Reply-To: <20230103195337.158625-1-bvanassche@acm.org>
On Tue, Jan 03, 2023 at 11:53:37AM -0800, Bart Van Assche wrote:
> Remove the code for fair tag sharing because it significantly hurts
> performance for UFS devices. Removing this code is safe because the
> legacy block layer worked fine without any equivalent fairness
> algorithm.
The legacy block layer didn't have a limited tag resource that can block
request allocations though, so I don't think we can appeal to that
example to conclude removing this is safe. As much as I'd like to get
rid of this code, I honestly have no idea if this isn't helping anyone.
> This algorithm hurts performance for UFS devices because UFS devices
> have multiple logical units. One of these logical units (WLUN) is used
> to submit control commands, e.g. START STOP UNIT. If any request is
> submitted to the WLUN, the queue depth is reduced from 31 to 15 or
> lower for data LUNs.
Can you give the WLUN it's own tagset instead?
next prev parent reply other threads:[~2023-01-18 22:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-03 19:53 [PATCH v2] block: Improve shared tag set performance Bart Van Assche
2023-01-18 21:20 ` Bart Van Assche
2023-01-18 22:14 ` Keith Busch [this message]
2023-01-18 22:46 ` Bart Van Assche
2023-01-19 17:48 ` Bart Van Assche
2023-01-19 18:47 ` Keith Busch
2023-01-19 19:28 ` Bart Van Assche
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