On Mon, 2019-06-24 at 15:51 +0200, Hervé Ballans wrote: > Hi everyone, > > We successfully use Ceph here for several years now, and since recently, > CephFS. > > From the same CephFS server, I notice a big difference between a fuse > mount and a kernel mount (10 times faster for kernel mount). It makes > sense to me (an additional fuse library versus a direct access to a > device...), but recently, one of our users asked me to explain him in > more detail the reason for this big difference...Hum... > > I then realized that I didn't really know how to explain the reasons to > him !! > > As well, does anyone have a more detailed explanation in a few words or > know a good web resource on this subject (I guess it's not specific to > Ceph but it's generic to all filesystems ?..) > > Thanks in advance, > Hervé > A lot of it is the context switching. Every time you make a system call (or other activity) that accesses a FUSE mount, it has to dispatch that request to the fuse device, the userland ceph-fuse daemon then has to wake up and do its thing (at least once) and then send the result back down to the kernel which then wakes up the original task so it can get the result. FUSE is a wonderful thing, but it's not really built for speed. -- Jeff Layton <jlayton@xxxxxxxxxxxxxxx> _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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