From: Jan Kara <jack@suse.cz>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Nikolai Grigoriev <ngrigoriev@gmail.com>,
linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-raid@vger.kernel.org, linux-mm@kvack.org,
Jens Axboe <axboe@kernel.dk>
Subject: Re: ext4 vs btrfs performance on SSD array
Date: Tue, 2 Sep 2014 16:20:24 +0200 [thread overview]
Message-ID: <20140902142024.GB19412@quack.suse.cz> (raw)
In-Reply-To: <20140902113104.GD5049@thunk.org>
On Tue 02-09-14 07:31:04, Ted Tso wrote:
> > - the very small max readahead size
>
> For things like the readahead size, that's probably something that we
> should autotune, based the time it takes to read N sectors. i.e.,
> start N relatively small, such as 128k, and then bump it up based on
> how long it takes to do a sequential read of N sectors until it hits a
> given tunable, which is specified in milliseconds instead of kilobytes.
Actually the amount of readahead we do is autotuned (based on hit rate).
So I would keep the setting in sysfs as the maximum size adaptive readahead
can ever read and we can bump it up. We can possibly add another feedback
into the readahead code to tune actualy readahead size depending on device
speed but we'd have to research exactly what algorithm would work best.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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next prev parent reply other threads:[~2014-09-02 14:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAEp=YLgzsLbmEfGB5YKVcHP4CQ-_z1yxnZ0tpo7gjKZ2e1ma5g@mail.gmail.com>
[not found] ` <20140902000822.GA20473@dastard>
2014-09-02 1:22 ` ext4 vs btrfs performance on SSD array Christoph Hellwig
2014-09-02 10:39 ` Zack Coffey
2014-09-02 11:31 ` Theodore Ts'o
2014-09-02 14:20 ` Jan Kara [this message]
2014-09-02 14:55 ` Theodore Ts'o
2014-09-02 12:55 ` Zack Coffey
2014-09-02 13:40 ` Austin S Hemmelgarn
2014-09-03 0:01 ` NeilBrown
2014-09-05 16:08 ` Christoph Hellwig
2014-09-05 16:40 ` Jeff Moyer
2014-09-05 16:50 ` Jens Axboe
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