计算机操作系统-Device-Manageme课件.ppt

1、 N e x t t r a c k a c c e s s e d n u m b e r o f t r a c k s t r a v e r s e d 5 5 4 5 5 8 3 3 9 1 9 1 8 2 1 9 0 7 2 1 6 0 7 0 1 5 0 1 0 3 8 1 1 2 1 8 4 1 4 6 T o t a l s e e k le n g t h 4 9 8 A v e r a g e s e e k le n g t h 5 5 .3 Next track Number of track traversed 90 10 58 32 55 3 39 16 38 1

2、 18 20 150 132 160 10 184 24 Total seek length 248 Average seek length 27.6 Next track Number of tracks traversed 150 50 160 10 184 24 90 94 58 32 55 3 39 16 38 1 18 20 total seek length 250 average seek length 27.8 Next track number of tracks traversed 150 50 160 10 184 24 18 166 38 20 39 1 55 16 58 3 90 32 total seek length 322 average seek length 35.8 New Section Old SectionRe-reference;count unchangedRe-reference;count:=count+1Miss(new block brought in)Count:=1( (a a) ) F FI IF FO O( (b b) ) U Us se e o of f T Th hr re ee e S Se ec ct ti io on ns sNew SectionMiddle SectionOld Section