Path: utzoo!attcan!uunet!clyde.concordia.ca!jarvis.csri.toronto.edu!daemon From: cks@white.toronto.edu (Chris Siebenmann) Newsgroups: comp.arch Subject: Re: X-terms v. PCs v. Workstations Message-ID: <89Dec18.164700est.27294@snow.white.toronto.edu> Date: 18 Dec 89 21:48:01 GMT References: <1498@aber-cs.UUCP> <89Dec5.151758est.27219@snow.white.toronto.edu> <1989Dec8.175416.26647@wucs1.wustl.edu> Sender: Organization: Ziebmef home away from home Lines: 33 [My apologies for the delay in reply; I got snowed under by real work. All of this data is for moderately used Ultrix 2.2 and 3.1 Vaxes.] jps@wucs1.wustl.edu (James Sterbenz) writes: [I mention surprising numbers from workload studies.] | Sounds interesting... | Can you give us some idea of what your surprising numbers look like? The buffer cache hit rate is very high (80% during a parallel kernel remake on a client machine, approaching 92% on a lightly used file/compute server). Even under heavy file I/O load (said kernel remake) name-to-inode resolution accounted for a good 45% of the block-level activity (more lightly-loaded systems see this soar to 50-60%), with cache hit rates of 96-99%. Asynchronous buffer writes range from 58% of writes (during the kernel remake) to 25% (average file/compute server activity). On the other hand, delayed writes are very worthwhile; about 75% of them are never actually written to disk during the kernel remake (presumably due to a second write filling the buffer up). Even during a kernel remake on an NFS-mounted partition, less than 21% of the blocks read or written were remote ones (at the filesystem level, about 80% of the reads and 44% of the writes were remote). There's an appallingly high level of symlink reading (probably due to the filesystem shuffling everyone is doing to accommodate multiple architectures and diskless clients); 19% of the system-level reads during the kernel remake were symlink reads (almost all from name-to-inode resolution), and this soars to 45% on our lightly loaded central machine. -- "I shall clasp my hands together and bow to the corners of the world." Number Ten Ox, "Bridge of Birds" cks@white.toronto.edu ...!{utgpu,utzoo,watmath}!utcsri!white!cks