Derek Atkins wrote: > "Chas Williams (CONTRACTOR)" <[EMAIL PROTECTED]> writes: > > >> In message <[EMAIL PROTECTED]>,"Brandon S. Allbe >> ry KF8NH" writes: >> >>> It used to be said (back when warlord was maintaining linux-afs and >>> Transarc 3.4a was the main release) that the memcache was much less >>> efficient than the disk cache and that it was better to use disk cache >>> in a ramdisk. Both have been pretty thoroughly overhauled since then, >>> though. >>> >> "efficient" isnt meaningful without context. memcache does use quite >> a bit of host memory. if your system is short on memory, memcache is >> not for you. however, memcache outperforms diskcache is most cases >> (ignoring say rereads over a link with high latency). >> > > In this case "efficient" was in terms of memory/space usage. For the > same memory usage the memcache will be able to hold fewer files > and less file data than a similarly-sized memdisk cache. > > >> the afs cache is handled by a seperate thread. the filesystem client >> requests a fetch from the cache manager. the cache manager does the >> fetch and writes the data into the cache. it signal the filesystem >> thread all is ready and the filesystem read reads the data. if you >> use a disk cache this is written to the disk and then read from the >> disk. memcache speeds this up a bit since you dont have the disk >> latency during this copy. >> > > Yes, it is definitely FASTER to use a memcache. However it is (was?) > more space efficient to use a ramdisk. > > >> i thought it might be interesting to make the filesystem thread give >> the cache manager a hint pointer, and the cache manager could memcpy >> the data to the filesystem thread buffers and write it to the disk. >> > > -derek > > Does the disk cache take advantage of linux's disk cache? I'm thinking that is a freebie if we use tmpfs or some other linux-provided fs-backed cache.
Jason _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
