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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53888DA9.6090003@redhat.com \
--to=heinzm@redhat.com \
--cc=linux-lvm@redhat.com \
--cc=rjones@redhat.com \
--cc=snitzer@redhat.com \
--cc=thornber@redhat.com \
--cc=zkabelac@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.