Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!sdd.hp.com!hplabs!hplabsz!renglish From: renglish@hplabsz.HP.COM (Bob English) Newsgroups: comp.arch Subject: Re: Sun bogosities, including MMU thrashing Message-ID: <6519@hplabsz.HP.COM> Date: 29 Jan 91 19:59:53 GMT References: <1991Jan10.214122.9506@news.arc.nasa.gov> <1991Jan25.185333.607@quick.com> Reply-To: renglish@hplabsz.UUCP (Bob English) Organization: Hewlett-Packard Laboratories Lines: 17 In article pcg@cs.aber.ac.uk (Piercarlo Grandi) writes: >Since as you seem to correctly >remember *most* files are under 8KB, this means that, as I have >remarked, internal fragmentation is countered by fragments on disk, but >not in the buffer cache. That all depends on what you think of as fragmentation. In most BSD systems, each buffer is allocated an 8KB virtual slot, which may or may not be backed by physical memory. The virtual space allocated is larger than the physical space used by the buffers. The virtual memory ends up highly fragmented, but that doesn't cost very much. Physical memory ends up much less fragmented, and if integrated into the global memory pool, can be used to hold program data as well as file system data. --bob-- renglish@hplabs.hp.com