All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christoph Nelles <evilazrael@evilazrael.de>
To: device-mapper development <dm-devel@redhat.com>
Subject: Re: DM-Cache Writeback & Direct IO?
Date: Thu, 09 Jul 2015 18:51:55 +0200	[thread overview]
Message-ID: <559EA6AB.2080603@evilazrael.de> (raw)
In-Reply-To: <20150708144829.GA5058@rh-vpn>

Hello Joe,

I updated to the latest kernel from Ubuntu mainline (4.2.0-040200rc1) 
and will rerun the same fio command over the night. Currently it shows 
the same behaviour. The fio command i use is
fio --name=test --filename=/dev/mapper/dmcache  --rw=randwrite 
--filesize=16G  --bs=64k --ioengine=libaio --direct=1 --iodepth=1000

After 4 runs, the status for the device mapper looks like this:
dmcache: 0 6442450943 cache 8 6029/4161600 512 2283/2913051 1517 119 
25120 1294780 0 2283 1484 1 writeback 2 migration_threshold 2048 smq 0 rw

Regards

Christoph



Am 08.07.2015 um 16:48 schrieb Joe Thornber:
> On Wed, Jul 08, 2015 at 11:03:42AM +0200, Christoph Nelles wrote:
>> Hi,
>>
>> Can the dm-cache writeback cache buffer direct IO or goes direct IO
>> always immediately to the origin device?
> Yes, the device mapper layer knows nothing about direct IO vs page
> cache IO.
>
>> I am currently performing tests and see that random direct write IO
>> never hits the cache, even after overwriting the same region over
>> and over.
> Could you try with the latest kernels and the new smq policy please?
>
> - Joe
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel

  reply	other threads:[~2015-07-09 16:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-08  9:03 DM-Cache Writeback & Direct IO? Christoph Nelles
2015-07-08 14:48 ` Joe Thornber
2015-07-09 16:51   ` Christoph Nelles [this message]
2015-07-21 13:51   ` Christoph Nelles
     [not found] <9E0DEE10BA62134F89BB5A513CA84BC3A1A6B5CA@MAILSERVER01.trt9a.local>
     [not found] ` <CAEZ+n-j_9QGWi7pdZY71VAmF-tnuRWb_8neWBd3iKMTm-yQU1A@mail.gmail.com>
2015-07-08 17:55   ` Leonardo Santos
2015-07-09 15:51     ` Christoph Nelles

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=559EA6AB.2080603@evilazrael.de \
    --to=evilazrael@evilazrael.de \
    --cc=dm-devel@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.