Re: [RFC PATCH 00/11] Rust null block driver

From: Niklas Cassel <Niklas.Cassel@wdc.com>
To: Andreas Hindborg <nmi@metaspace.dk>
Cc: "Jens Axboe" <axboe@kernel.dk>, "Christoph Hellwig" <hch@lst.de>,
	"Keith Busch" <kbusch@kernel.org>,
	"Damien Le Moal" <Damien.LeMoal@wdc.com>,
	"Hannes Reinecke" <hare@suse.de>,
	"lsf-pc@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>,
	"rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"Andreas Hindborg" <a.hindborg@samsung.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"open list" <linux-kernel@vger.kernel.org>,
	"gost.dev@samsung.com" <gost.dev@samsung.com>
Subject: Re: [RFC PATCH 00/11] Rust null block driver
Date: Wed, 3 May 2023 11:32:44 +0000	[thread overview]
Message-ID: <ZFJGWwlRbSS3zFnc@x1-carbon> (raw)
In-Reply-To: <20230503090708.2524310-1-nmi@metaspace.dk>

On Wed, May 03, 2023 at 11:06:57AM +0200, Andreas Hindborg wrote:
> From: Andreas Hindborg <a.hindborg@samsung.com>
> 

(cut)

> 
> For each measurement the drivers are loaded, a drive is configured with memory
> backing and a size of 4 GiB. C null_blk is configured to match the implemented
> modes of the Rust driver: `blocksize` is set to 4 KiB, `completion_nsec` to 0,
> `irqmode` to 0 (IRQ_NONE), `queue_mode` to 2 (MQ), `hw_queue_depth` to 256 and
> `memory_backed` to 1. For both the drivers, the queue scheduler is set to
> `none`. These measurements are made using 30 second runs of `fio` with the
> `PSYNC` IO engine with workers pinned to separate CPU cores. The measurements
> are done inside a virtual machine (qemu/kvm) on an Intel Alder Lake workstation
> (i5-12600).

Hello Andreas,

I'm curious why you used psync ioengine for the benchmarks.

As psync is a sync ioengine, it means queue depth == 1.

Wouldn't it have been more interesting to see an async ioengine,
together with different queue depths?

You might want to explain your table a bit more.
It might be nice to see IOPS and average latencies.

As an example of a table that I find easier to interpret,
see e.g. the table on page 29 in the SPDK performance report:
https://ci.spdk.io/download/performance-reports/SPDK_nvme_bdev_perf_report_2301.pdf

Kind regards,
Niklas