From ccbd8543c5ad589e878a3924b2dd39d5a6a2f39d Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Fri, 8 Dec 2006 14:35:09 +0000 Subject: [PATCH] Explain better what we expect from the buffer cache. --- doc/filesys.texi | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/doc/filesys.texi b/doc/filesys.texi index 9075c9a..1b666b3 100644 --- a/doc/filesys.texi +++ b/doc/filesys.texi @@ -287,11 +287,12 @@ disk. Otherwise, fetch the block from disk into cache, evicting an older entry if necessary. You are limited to a cache no greater than 64 sectors in size. -Be sure to choose an intelligent cache replacement algorithm. -Experiment to see what combination of accessed, dirty, and other -information results in the best performance, as measured by the number -of disk accesses. For example, metadata is generally more valuable to -cache than data. +You must implement a cache replacement algorithm that is at least as +good as the ``clock'' algorithm. Your algorithm must also account for +the generally greater value of metadata compared to data. Experiment +to see what combination of accessed, dirty, and other information +results in the best performance, as measured by the number of disk +accesses. You can keep a cached copy of the free map permanently in memory if you like. It doesn't have to count against the cache size. -- 2.30.2