glusterfs.git/xlators/cluster/dht/src/dht.c, branch v3.6.0beta3

glusterfs: zerofill support

2013-11-11T05:25:49+00:00

Add support for a new ZEROFILL fop. Zerofill writes zeroes to a file in
the specified range. This fop will be useful when a whole file needs to
be initialized with zero (could be useful for zero filled VM disk image
provisioning or  during scrubbing of VM disk images).

Client/application can issue this FOP for zeroing out. Gluster server
will zero out required range of bytes ie server offloaded zeroing. In
the absence of this fop,  client/application has to repetitively issue
write (zero) fop to the server, which is very inefficient method because
of the overheads involved in RPC calls  and acknowledgements.

WRITESAME is a  SCSI T10 command that takes a block of data as input and
writes the same data to other blocks and this write is handled
completely within the storage and hence is known as offload . Linux ,now
has support for SCSI WRITESAME command which is exposed to the user in
the form of BLKZEROOUT ioctl.  BD Xlator can exploit BLKZEROOUT ioctl to
implement this fop. Thus zeroing out operations can be completely
offloaded to the storage device , making it highly efficient.

The fop takes two arguments offset and size. It zeroes out 'size' number
of bytes in an opened file starting from 'offset' position.

This patch adds zerofill support to the following areas:
	- libglusterfs
	- io-stats
	- performance/md-cache,open-behind
	- quota
	- cluster/afr,dht,stripe
	- rpc/xdr
	- protocol/client,server
	- io-threads
	- marker
	- storage/posix
	- libgfapi

Client applications can exloit this fop by using glfs_zerofill introduced in
libgfapi.FUSE support to this fop has not been added as there is no system call
for this fop.

Changes from previous version 3:
* Removed redundant memory failure log messages

Changes from previous version 2:
* Rebased and fixed build error

Changes from previous version 1:
* Rebased for latest master

TODO :
     * Add zerofill support to trace xlator
     * Expose zerofill capability as part of gluster volume info

Here is a performance comparison of server offloaded zeofill vs zeroing
out using repeated writes.

[root@llmvm02 remote]# time ./offloaded aakash-test log 20

real	3m34.155s
user	0m0.018s
sys	0m0.040s
[root@llmvm02 remote]# time ./manually aakash-test log 20

real	4m23.043s
user	0m2.197s
sys	0m14.457s
[root@llmvm02 remote]# time ./offloaded aakash-test log 25;

real	4m28.363s
user	0m0.021s
sys	0m0.025s
[root@llmvm02 remote]# time ./manually aakash-test log 25

real	5m34.278s
user	0m2.957s
sys	0m18.808s

The argument log is a file which we want to set for logging purpose and
the third argument is size in GB .

As we can see there is a performance improvement of around 20% with this
fop.

Change-Id: I081159f5f7edde0ddb78169fb4c21c776ec91a18
BUG: 1028673
Signed-off-by: Aakash Lal Das 
Signed-off-by: M. Mohan Kumar 
Reviewed-on: http://review.gluster.org/5327
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

glusterfs: discard (hole punch) support

2013-06-13T21:37:43+00:00

Add support for the DISCARD file operation. Discard punches a hole
in a file in the provided range. Block de-allocation is implemented
via fallocate() (as requested via fuse and passed on to the brick
fs) but a separate fop is created within gluster to emphasize the
fact that discard changes file data (the discarded region is
replaced with zeroes) and must invalidate caches where appropriate.

BUG: 963678
Change-Id: I34633a0bfff2187afeab4292a15f3cc9adf261af
Signed-off-by: Brian Foster 
Reviewed-on: http://review.gluster.org/5090
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

gluster: add fallocate fop support

2013-06-13T21:37:21+00:00

Implement support for the fallocate file operation. fallocate
allocates blocks for a particular inode such that future writes
to the associated region of the file are guaranteed not to fail
with ENOSPC.

This patch adds fallocate support to the following areas:

	- libglusterfs
	- mount/fuse
	- io-stats
	- performance/md-cache,open-behind
	- quota
	- cluster/afr,dht,stripe
	- rpc/xdr
	- protocol/client,server
	- io-threads
	- marker
	- storage/posix
	- libgfapi

BUG: 949242
Change-Id: Ice8e61351f9d6115c5df68768bc844abbf0ce8bd
Signed-off-by: Brian Foster 
Reviewed-on: http://review.gluster.org/4969
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

dht: make nufa/switch call dht's init/fini

2013-04-03T22:16:24+00:00

These functions keep changing as new functionality is added, so copying
and pasting the code is not a good solution.  This way ensures that all
fields get initialized properly no matter how much new stuff we throw in.

Change-Id: I9e9b043d2d305d31e80cf5689465555b70312756
BUG: 924488
Signed-off-by: Jeff Darcy 
Reviewed-on: http://review.gluster.org/4710
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

dht: make DHT xattr names configurable

2013-03-21T22:04:31+00:00

This is necessary to support "DHT over DHT" configurations, so that the
upper and lower instances of DHT don't step all over each other.  Why
would we even consider such a thing?  Because it gives us the ability to
do data tiering and rack-aware placement, either by themselves or as
complements to other functionality such as erasure codes or
deduplication which save space but cost performance.  By setting up the
top-level DHT to place data into one of several lower-level DHT pools
based on policy instead of pure elastic hashing, we get better
performance for 90% of accesses and better storage efficiency for 90% of
data, all for relatively low effort.

Change-Id: I72e65c29edfc80babf39f7a2a00090f4588c4070
BUG: 924265
Signed-off-by: Jeff Darcy 
Reviewed-on: http://review.gluster.org/4694
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

glusterd: Added the validation function for subvols-per-directory

2013-02-28T19:31:28+00:00

Change-Id: Ie2259023b9001311a2032792639c3093054f6750
BUG: 896431
Signed-off-by: Avra Sengupta 
Reviewed-on: http://review.gluster.org/4552
Reviewed-by: Jeff Darcy 
Tested-by: Gluster Build System

cluster/distribute: Add filter to support file patterns to be migrated

2013-02-27T20:16:07+00:00

'gluster volume rebalance' command will be enhanced to support passing of these
options/pattern.

 is comma separated list as show below. The Precedence is from right
to left.

e.g- "*avi,*pdf:10MB,*:1KB"
     The precedence is as follows:
     migrate all files with size equal or greater than 1KB "*:1KB"
     migrate all pdf files with size equal or greater than 10MB "*pdf:10MB"
     migrate all avi files "*avi"

With this option, it is possible to choose which files to migrate.

Change-Id: I6d6d6a015bcbacf1debae2f278a2d92306fb055d
BUG: 896456
Signed-off-by: shishir gowda 
Reviewed-on: http://review.gluster.org/4366
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

distribute: add hash-name-regex option

2013-02-19T04:50:48+00:00

This is to support the common "write to temp file then rename" idiom. In our
case this causes us to create a linkfile during the rename in (N-1)/N cases,
with a significant impact on performance e.g. for UFO which uses this idiom.
This patch allows the user to specify up to two regular expressions that
separate the permanent and transient parts of a temp-file name:

    rsync-hash-regex reimplements the existing RSYNC_FRIENDLY_NAME
    pattern where the temporary name for EXAMPLE is .EXAMPLE.suffix

    extra-hash-regex can be used for a second pattern, active concurrently,
    and can include alternatives via the POSIX extended-regex syntax

Change-Id: Ic1a6ed19324bc31fefe91ee34b8478877a9c5d2c
BUG: 912564
Signed-off-by: Jeff Darcy 
Reviewed-on: http://review.gluster.org/4116
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

glusterd/cli: Updated the options descriptions for "volume set help"

2013-01-22T07:03:57+00:00

Change-Id: I0db00b7334bb9707ab48bd661ac03a3ad818d6e4
BUG: 893458
Signed-off-by: Avra Sengupta 
Reviewed-on: http://review.gluster.org/4393
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/distribute: re-set layouts to prevent overlaps

2012-12-12T00:05:50+00:00

When subvols-per-directory option is used, with bricks addition/removal
the layouts might get distributed to other subvols, which were not part
of the layout before. We need to clean up layouts on old subvolumes, to
prevent overlaps.

Also, we need to make sure if layout-cnt is never less
than subvolume-cnt.

Change-Id: I00994a092ca0c99aedcc41bd9412d43460f88a04
BUG: 884455
Signed-off-by: shishir gowda 
Reviewed-on: http://review.gluster.org/4281
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati