J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > Say I had a hypothetical, err, friend, who hadn't been following that > FS-Cache work--could you summarize the advantages it bring us? https://lore.kernel.org/linux-nfs/159465784033.1376674.18106463693989811037.stgit@xxxxxxxxxxxxxxxxxxxxxx/T/#t - Makes the caching code a lot simpler (~2400 LoC removed, ~1000 LoDoc[*] removed at the moment from fscache, cachefiles and afs). - Stops using bmap to work out what data is cached. This isn't reliable with modern extend-based filesystems. A bitmap of cached granules is saved in an xattr instead. - Uses async DIO (kiocbs) to do I/O to/from the cache rather than using buffered writes (kernel_write) and pagecache snooping for read (don't ask). - A lot faster and less CPU intensive as there's no page-to-page copying. - A lot less VM pressure as it doesn't have duplicate pages in the backing fs that aren't really accounted right. - Uses tmpfiles+link to better handle invalidation. It will at some point hopefully employ linkat(AT_LINK_REPLACE) to effect cut-over on disk rather than unlink,link. David [*] The upstream docs got ReSTified, so the doc patches I have are now useless and need reworking:-(.
