[Gluster-users] [Gluster-devel] Need a way to display and flush gluster cache ?

[Niels de Vos]

On Tue, Jul 26, 2016 at 12:43:56PM +0530, Kaushal M wrote:
> On Tue, Jul 26, 2016 at 12:28 PM, Prashanth Pai <ppai at redhat.com> wrote:
> > +1 to option (2) which similar to echoing into /proc/sys/vm/drop_caches
> >
> >  -Prashanth Pai
> >
> > ----- Original Message -----
> >> From: "Mohammed Rafi K C" <rkavunga at redhat.com>
> >> To: "gluster-users" <gluster-users at gluster.org>, "Gluster Devel" <gluster-devel at gluster.org>
> >> Sent: Tuesday, 26 July, 2016 10:44:15 AM
> >> Subject: [Gluster-devel] Need a way to display and flush gluster cache ?
> >>
> >> Hi,
> >>
> >> Gluster stack has it's own caching mechanism , mostly on client side.
> >> But there is no concrete method to see how much memory are consuming by
> >> gluster for caching and if needed there is no way to flush the cache memory.
> >>
> >> So my first question is, Do we require to implement this two features
> >> for gluster cache?
> >>
> >>
> >> If so I would like to discuss some of our thoughts towards it.
> >>
> >> (If you are not interested in implementation discussion, you can skip
> >> this part :)
> >>
> >> 1) Implement a virtual xattr on root, and on doing setxattr, flush all
> >> the cache, and for getxattr we can print the aggregated cache size.
> >>
> >> 2) Currently in gluster native client support .meta virtual directory to
> >> get meta data information as analogues to proc. we can implement a
> >> virtual file inside the .meta directory to read  the cache size. Also we
> >> can flush the cache using a special write into the file, (similar to
> >> echoing into proc file) . This approach may be difficult to implement in
> >> other clients.
> 
> +1 for making use of the meta-xlator. We should be making more use of it.

Indeed, this would be nice. Maybe this can also expose the memory
allocations like /proc/slabinfo.

The io-stats xlator can dump some statistics to
/var/log/glusterfs/samples/ and /var/lib/glusterd/stats/ . That seems to
be acceptible too, and allows to get statistics from server-side
processes without involving any clients.

HTH,
Niels


> 
> >>
> >> 3) A cli command to display and flush the data with ip and port as an
> >> argument. GlusterD need to send the op to client from the connected
> >> client list. But this approach would be difficult to implement for
> >> libgfapi based clients. For me, it doesn't seems to be a good option.
> >>
> >> Your suggestions and comments are most welcome.
> >>
> >> Thanks to Talur and Poornima for their suggestions.
> >>
> >> Regards
> >>
> >> Rafi KC
> >>
> >> _______________________________________________
> >> Gluster-devel mailing list
> >> Gluster-devel at gluster.org
> >> http://www.gluster.org/mailman/listinfo/gluster-devel
> >>
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