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From: Matthew Wilcox <willy@infradead.org>
To: Keith Busch <kbusch@kernel.org>
Cc: Viacheslav Dubeyko <slava@dubeyko.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.de>,
	lsf-pc@lists.linuxfoundation.org, linux-mm@kvack.org,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Subject: Re: [LSF/MM/BPF TOPIC] Large block for I/O
Date: Fri, 22 Dec 2023 16:06:08 +0000	[thread overview]
Message-ID: <ZYWz8K98YUGf/VZp@casper.infradead.org> (raw)
In-Reply-To: <ZYWm_tMtfrKaNf3t@kbusch-mbp>

On Fri, Dec 22, 2023 at 08:10:54AM -0700, Keith Busch wrote:
> If the host really wants to write in small granularities, then larger
> block sizes just shifts the write amplification from the device to the
> host, which seems worse than letting the device deal with it.

Maybe?  I'm never sure about that.  See, if the drive is actually
managing the flash in 16kB chunks internally, then the drive has to do a
RMW which is increased latency over the host just doing a 16kB write,
which can go straight to flash.  Assuming the host has the whole 16kB in
memory (likely?)  Of course, if you're PCIe bandwidth limited, then a
4kB write looks more attractive, but generally I think drives tend to
be IOPS limited not bandwidth limited today?



  reply	other threads:[~2023-12-22 16:06 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <7970ad75-ca6a-34b9-43ea-c6f67fe6eae6@iogearbox.net>
2023-12-20 10:01 ` LSF/MM/BPF: 2024: Call for Proposals Daniel Borkmann
2023-12-20 15:03   ` [LSF/MM/BPF TOPIC] Large block for I/O Hannes Reinecke
2023-12-21 20:33     ` Bart Van Assche
2023-12-21 20:42       ` Matthew Wilcox
2023-12-21 21:00         ` Bart Van Assche
2023-12-22  5:09       ` Christoph Hellwig
2023-12-22  5:13       ` Matthew Wilcox
2023-12-22  5:37         ` Christoph Hellwig
2024-01-08 19:30           ` Bart Van Assche
2024-01-08 19:35             ` Matthew Wilcox
2024-02-22 18:45               ` Luis Chamberlain
2024-02-25 23:09                 ` Dave Chinner
2024-02-26 15:25                   ` Luis Chamberlain
2024-03-07  1:59                     ` Luis Chamberlain
2024-03-07  5:31                       ` Dave Chinner
2024-03-07  7:29                         ` Luis Chamberlain
2023-12-22  8:23       ` Viacheslav Dubeyko
2023-12-22 12:29         ` Hannes Reinecke
2023-12-22 13:29           ` Matthew Wilcox
2023-12-22 15:10         ` Keith Busch
2023-12-22 16:06           ` Matthew Wilcox [this message]
2023-12-25  8:55             ` Viacheslav Dubeyko
2023-12-25  8:12           ` Viacheslav Dubeyko
2024-02-23 16:41     ` Pankaj Raghav (Samsung)
2024-01-17 13:37   ` LSF/MM/BPF: 2024: Call for Proposals [Reminder] Daniel Borkmann
2024-02-14 13:03     ` LSF/MM/BPF: 2024: Call for Proposals [Final Reminder] Daniel Borkmann

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