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#! rnews 1934 bsd Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!munnari.OZ.AU!metro!metro!asstdc.scgt.oz.au!nsw.news.telstra.net!act.news.telstra.net!imci3!newsfeed.internetmci.com!in2.uu.net!01-newsfeed.univie.ac.at!news.iif.hu!ludens.elte.hu!not-for-mail Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Linux vs. FreeBSD ... (FreeBSD extremely mem/swap hungry) Message-ID: <31a9c16e.0@kaliban.csoma.elte.hu> From: mingo@kaliban.csoma.elte.hu (Ingo Molnar) Date: 27 May 96 14:51:26 GMT References: <3188C1E2.45AE@onramp.net> <4o3ftc$4rc@zot.io.org> Nntp-Posting-Host: kaliban.csoma.elte.hu X-Newsreader: TIN [UNIX 1.3 BETA-950824-color PL0] Lines: 27 Terry Lambert (terry@lambert.org) wrote: : Note: sbrk'ing pages back to the system, like the GNU malloc used : on Linux does, is less efficient than calling munmap. This is i think the 5.3.* Linux libc series are doing mmap based malloc. : What's wasteful is that Linux has all this high speed access RAM : (physical memory) and all this medium speed access RAM (swap) and : all this low speed access RAM (the disk, and the program images : being used as swap store), and it is preferentially discarding : perfectly good medium speed access pages in favor of low speed : access pages and making the numbers you are misinterpreting look : "good". the filesystem is "medium speed" on Linux. You can read/write files at disk hardware speed under ext2fs (using the proper busmastering hardware). Linux isnt swapping code too good, it's rather for swapping >data<, not code. Linux is optimized for "random data access", if we talk about swapping. There is no readahead in the swap space AFAIR. (there was some discussion about sequential data swapping used in many scientific calculations, but there is no code in the kernel yet) A well-installed filesystem has properly placed files, there is very low overhead in reading them. -- mingo