Leal, ZFS uses the DNLC. It still provides the fastest lookup of <directory, name> to vnode. The DNLC is kind of LRU. An async process will use a rotor to move through the hash chains and select the LRU entry but will select first negative cache entries and vnodes only referenced by the DNLC. Underlying this ZFS uses the ZAP and Fat ZAP to store the mappings.
ZFS does not use the 2nd level DNLC which allows caching of directories. This is only used by UFS to avoid a linear search of large directories. Neil. On 10/30/08 04:50, Marcelo Leal wrote: > Hello, > In ZFS the DNLC concept is gone, or is in ARC too? I mean, all the cache in > ZFS is ARC right? > I was thinking if we can tune the DNLC in ZFS like in UFS.. if we have too > *many* files and > directories, i guess we can have a better performance having all the > metadata cached, and that > is even more important in NFS operations. > DNLC is LRU right? And ARC should be totally dynamic, but as in another > thread here, > i think reading a *big* file can mess with the whole thing. Can we hold an > area in memory > for DNLC cache, or that is not the ARC way? > > thanks, > > Leal. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
