From: Heinz Mauelshagen <heinzm@redhat.com>
To: "Richard W.M. Jones" <rjones@redhat.com>,
Mike Snitzer <snitzer@redhat.com>
Cc: Zdenek Kabelac <zkabelac@redhat.com>,
thornber@redhat.com,
LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Testing the new LVM cache feature
Date: Fri, 30 May 2014 15:54:49 +0200 [thread overview]
Message-ID: <53888DA9.6090003@redhat.com> (raw)
In-Reply-To: <20140530134642.GL1302@redhat.com>
On 05/30/2014 03:46 PM, Richard W.M. Jones wrote:
> I have now set both read_promote_adjustment ==
> write_promote_adjustment == 0 and used drop_caches between runs.
Did you adjust "sequential_threshold 0" as well?
dm-cache tries to avoid promoting large sequential files to the cache,
because spindles have good bandwidth.
This is again because of the hot spot caching nature of dm-cache.
>
> I also read Documentation/device-mapper/cache-policies.txt at Heinz's
> suggestion.
>
> I'm afraid the performance of the fio test is still not the same as
> the SSD (4.8 times slower than the SSD-only test now).
>
> Would repeated runs of (md5sum virt.* ; echo 3 > /proc/sys/vm/drop_caches)
> not eventually cause the whole file to be placed on the SSD?
> It does seem very counter-intuitive if not.
Please retry with "sequential_threshold 0"
Heinz
>
> Rich.
next prev parent reply other threads:[~2014-05-30 13:54 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-22 10:18 [linux-lvm] Testing the new LVM cache feature Richard W.M. Jones
2014-05-22 14:43 ` Zdenek Kabelac
2014-05-22 15:22 ` Richard W.M. Jones
2014-05-22 15:49 ` Richard W.M. Jones
2014-05-22 18:04 ` Mike Snitzer
2014-05-22 18:13 ` Richard W.M. Jones
2014-05-29 13:52 ` Richard W.M. Jones
2014-05-29 20:34 ` Mike Snitzer
2014-05-29 20:47 ` Richard W.M. Jones
2014-05-29 21:06 ` Mike Snitzer
2014-05-29 21:19 ` Richard W.M. Jones
2014-05-29 21:58 ` Mike Snitzer
2014-05-30 9:04 ` Richard W.M. Jones
2014-05-30 10:30 ` Richard W.M. Jones
2014-05-30 13:38 ` Mike Snitzer
2014-05-30 13:40 ` Richard W.M. Jones
2014-05-30 13:42 ` Heinz Mauelshagen
2014-05-30 13:54 ` Richard W.M. Jones
2014-05-30 13:58 ` Zdenek Kabelac
2014-05-30 13:46 ` Richard W.M. Jones
2014-05-30 13:54 ` Heinz Mauelshagen [this message]
2014-05-30 14:26 ` Richard W.M. Jones
2014-05-30 14:29 ` Mike Snitzer
2014-05-30 14:36 ` Richard W.M. Jones
2014-05-30 14:44 ` Mike Snitzer
2014-05-30 14:51 ` Richard W.M. Jones
2014-05-30 14:58 ` Mike Snitzer
2014-05-30 15:28 ` Richard W.M. Jones
2014-05-30 18:16 ` Mike Snitzer
2014-05-30 20:53 ` Mike Snitzer
2014-05-30 13:55 ` Mike Snitzer
2014-05-30 14:29 ` Richard W.M. Jones
2014-05-30 14:36 ` Mike Snitzer
2014-05-30 11:53 ` Mike Snitzer
2014-05-30 11:38 ` Alasdair G Kergon
2014-05-30 11:45 ` Alasdair G Kergon
2014-05-30 12:45 ` Werner Gold
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