Gentoo Forums
Gentoo Forums
Gentoo Forums
Quick Search: in
New Reiser4 feature - Discard (Trim) support for SSDs
View unanswered posts
View posts from last 24 hours

 
Reply to topic    Gentoo Forums Forum Index Unsupported Software
View previous topic :: View next topic  
Author Message
dusanc
Apprentice
Apprentice


Joined: 19 Sep 2005
Posts: 219
Location: Serbia

PostPosted: Tue May 06, 2014 7:14 am    Post subject: New Reiser4 feature - Discard (Trim) support for SSDs Reply with quote

So if you have an SSD and heard about Trim feature http://en.wikipedia.org/wiki/Trim_%28computing%29 you can use it now with your Reiser4 partitions with following patches using "discard" mount option:

http://marc.info/?l=reiserfs-devel&m=139935424207357&w=2

PS. Drives with specs <SATA3.1 may slow down as trim is slow and not queued on them http://en.wikipedia.org/wiki/Trim_%28computing%29#Shortcomings
_________________
Reiser4 Gentoo FAQ [06May2014]
Back to top
View user's profile Send private message
dusanc
Apprentice
Apprentice


Joined: 19 Sep 2005
Posts: 219
Location: Serbia

PostPosted: Sat Aug 09, 2014 11:11 pm    Post subject: Reply with quote

Discard/trim option is out for 3.15

Quote:
Hello everyone,

Ivan Shapovalov kindly implemented discard support for us.

Now SSD users can mount their reiser4 partitions with the option
"discard" and the file system will issue discard requests to inform
the device that blocks are not longer used.

In reiser4 issuing discard requests is a delayed action (like many
other actions including block allocation, compression, etc). It means
that discard requests are accumulated as the release of blocks and
issued as background process after issuing of all other usual
requests.

Such delayed technique allows to issue discard requests of better
quality, because the discard requests get merged in the process of
accumulation. Another advantage of the delayed discard is that the
"non-queued TRIM" is not a problem for us.


Implementation notes


Managing discard requests is a business of reiser4 transaction
manager. This is because blocks deallocation is a kind of events
which are tracked by the transaction manager. Deallocted extents
are captured by a respective transaction atom. At commit time all
the extents are sorted, merged and discarded right after overwriting
journalled blocks at their permanent location on disk. After issuing
the discard requests we complete the transaction by deallocating
respective blocks at working bitmap (which always resides in memory).
Thus, we guarantee consistency (nobody touches our extents before
discard completion). We don't record information about discard
extents in the journal. The worst thing that can happen after system
crash is missing a number of discard requests. It doesn't break
consistency of the file systems however. For such unpleasant
situations we'll provide support of FITRIM ioctl later.

Also in plans: garbage collection at the head and tail of every
extent to be discarded. The algorithms are complicated, however,
the game is worth the candle.
The patch against reiser4-for-3.15 can be found here:
http://sourceforge.net/projects/reiser4/files/patches/

WARNING: Don't use it for important data for now. Even in the case
of no visible problems, please, check your partition by fsck.reiser4
as frequently as possible. Report about found inconsistency.


Discard support in reiser4progs:


When formatting your SSD partition by mkfs.reiser4 use the option -d:
it will issue discard request for the whole partition before creating
reiser4 structure on it. This option is available in reiser4progs-1.0.9,
please find here:
http://sourceforge.net/projects/reiser4/files/reiser4-utils/reiser4progs

In order to build reiser4progs-1.0.9 you will need libaal-1.0.6,
please find here:
http://sourceforge.net/projects/reiser4/files/reiser4-utils/libaal

Thanks,
Edward.

_________________
Reiser4 Gentoo FAQ [06May2014]
Back to top
View user's profile Send private message
Display posts from previous:   
Reply to topic    Gentoo Forums Forum Index Unsupported Software All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum