linux-kernel - Re: [PATCH v6 2/2] zonefs: Add documentation

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Date:   Wed, 15 Jan 2020 06:23:21 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Randy Dunlap <rdunlap@...radead.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Johannes Thumshirn <jth@...nel.org>,
        Naohiro Aota <Naohiro.Aota@....com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH v6 2/2] zonefs: Add documentation

Randy,

On 2020/01/15 3:25, Randy Dunlap wrote:
> Hi Damien,
> 
> Here are a few editorial comments for you...

Thanks ! All fixed.

[...]
>> +For sequential write zone files, the file size changes as data is appended at
>> +the end of the file, similarly to any regular file system.
>> +
>> +# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
>> +1+0 records in
>> +1+0 records out
>> +4096 bytes (4.1 kB, 4.0 KiB) copied, 1.05112 s, 3.9 kB/s
> 
> Still slow.  You don't want to change that?

Good catch. I thought I had fixed that. Here is the updated dd run,
after making sure that the disk has woken up from low power state before
running:

dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
1+0 records in
1+0 records out
4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00044121 s, 9.3 MB/s

The HDD write cache is on and empty at the time of running this, which
explains the much lower I/O time.

-- 
Damien Le Moal
Western Digital Research