[Gluster-devel] Turning off readdirp in the entire stack on fuse mount

[Raghavendra Gowdappa]

----- Original Message -----
> From: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> To: "Gluster Devel" <gluster-devel at gluster.org>, "gluster-users" <gluster-users at gluster.org>
> Sent: Thursday, March 2, 2017 9:48:08 AM
> Subject: Turning off readdirp in the entire stack on fuse mount
> 
> Hi all,
> 
> One of the grey areas (in terms of documentation) is how to turn off
> readdirplus (aka readdirp) in the entire stack of glusterfs. The confusion
> is because, there are couple of xlators which by default convert a readdir
> into readdirp. All of the following steps need to be done to turn off
> readdirp entirely.
> 
> 1. mount glusterfs with option --use-readdirp=no (disables readdirp between
> fuse kernel module and glusterfs)
> 
> [root at unused glusterfs]# mount -t glusterfs booradley:/testvol -o
> use-readdirp=no /mnt/glusterfs
> 
> [root at unused glusterfs]# ps ax | grep -i mnt
> 26096 ?        Ssl    0:00 /usr/local/sbin/glusterfs --use-readdirp=no
> --volfile-server=booradley --volfile-id=/testvol /mnt/glusterfs
> 
> 2. set performance.force-readdirp to false (prevents md-cache from converting
> readdir calls to readdirp)
> [root at unused glusterfs]# gluster volume set testvol
> performance.force-readdirp off
> volume set: success
> 
> 3. set dht.force-readdirp to false (prevents dht from converting readdir into
> readdirp
> [root at unused glusterfs]# gluster volume set testvol dht.force-readdirp off
> volume set: success
> 
> [root at unused glusterfs]# gluster volume info testvol
>  
> Volume Name: testvol
> Type: Distribute
> Volume ID: 007edfec-0e54-4d80-bef4-9aec5bcc1108
> Status: Started
> Snapshot Count: 0
> Number of Bricks: 1
> Transport-type: tcp
> Bricks:
> Brick1: booradley:/home/export/testvol
> Options Reconfigured:
> dht.force-readdirp: off
> performance.force-readdirp: off
> transport.address-family: inet
> nfs.disable: on
> 
> Note that if readdir-ahead is turned on, by default it does prefetch
> directory entries to fill its cache using readdirp. However, it doesn't
> implement readdirp fop. 

s/readdirp fop/readdir fop/

> Hence those prefetched entries are never consumed in
> the above configuration. If option performance.readdir-ahead is set to off,
> we wouldn't not witness a readdirp fop in the entire glusterfs stack (from
> fuse till bricks).
> 
> regards,
> Raghavendra