On Tue, 24 Mar 2009, Robert Watson wrote:
Add DTrace probes to the NFS access and attribute caches. Access cache
events are:
nfsclient:accesscache:flush:done
nfsclient:accesscache:get:hit
nfsclient:accesscache:get:miss
nfsclient:accesscache:load:done
They pass the vnode, uid, and requested or loaded access mode (if any);
the load event may also report a load error if the RPC fails.
The attribute cache events are:
nfsclient:attrcache:flush:done
nfsclient:attrcache:get:hit
nfsclient:attrcache:get:miss
nfsclient:attrcache:load:done
They pass the vnode, optionally the vattr if one is present (hit or load),
and in the case of a load event, also a possible RPC error.
This will probably want to be changed in a few ways before we consider it
done, but I've found it quite useful already in understanding our NFS client
and how the various caches interact. Typical trace output might look like
this, combining the previously committed NFSv3 RPC tracing with cache tracing:
bin syscall module probe vnode *
---- ------------- ----------- ------------- ----------
ls lstat attrcache get:hit 3282019108
ls stat attrcache get:hit 3282019108
ls open accesscache get:hit 3282019108
ls open attrcache flush:done 3282019108
ls open attrcache get:miss 3282019108
ls open nfs3 getattr:start 3282019108
ls open nfs3 getattr:done 3282019108
ls fstat attrcache get:hit 3282019108
ls fstatfs nfs3 fsstat:start 3282019108
ls fstatfs nfs3 fsstat:done 3282019108
ls fstat attrcache get:hit 3282019108
ls fchdir accesscache get:hit 3282019108
ls getdirentries attrcache get:hit 3282019108
ls lstat accesscache get:hit 3282019108
ls lstat attrcache get:hit 3281944576
ls lstat attrcache get:hit 3281944576
ls getdirentries attrcache get:hit 3282019108
ls pathconf accesscache get:hit 3282019108
ls pathconf attrcache get:hit 3281944576
If you're using this on a multi-CPU box, make sure your probes trace
timestamps and that you sort by them, if you require ordering, since NFS tends
to bounce around a bit, especially for loopback NFS testing. :-)
Robert N M Watson
Computer Laboratory
University of Cambridge
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