I'm investigating a performance issue, and vmstat is showing: procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 4 3 846000 162048 1220 3002540 596 0 70008 766 18552 15943 3 6 67 24 2 3 845824 159284 1220 3008828 1116 0 73108 17183 17748 14786 6 11 54 28 0 4 845816 212872 1220 2958544 4 0 51452 57134 19235 16206 4 10 58 27 6 1 845812 156088 1220 3010976 4 0 65652 991 15372 13947 1 3 75 20 0 0 845808 167580 1220 3006876 0 0 63668 12689 20513 13451 2 4 84 9 1 0 845808 163356 1220 3011124 0 0 32868 80 11735 12122 1 2 93 4 0 1 845788 161248 1228 3008176 20 0 41712 540 13442 14301 1 3 88 8 1 0 845780 162364 1228 3012860 16 0 70844 13689 20596 16787 4 6 79 12 2 2 845756 162736 1228 3013604 112 0 36804 32394 16490 16794 1 4 78 16 3 1 845752 159280 1228 3009800 24 0 82608 890 17589 14989 2 5 69 23 0 3 845688 161016 1228 3017948 104 0 90356 25875 24452 15321 3 8 72 16 1 3 845580 163248 1228 3008712 208 0 84528 12806 20642 14609 3 5 71 20 0 1 845516 160536 1228 3019424 56 0 60240 16853 16595 13174 2 4 78 16 1 0 845444 166364 1228 3012828 76 0 22652 1674 12705 12765 1 2 91 6 There is activity in the si column, and iostat on the swap device is showing some activity. I'm wondering if 'si' also includes activity on memory mapped files, or if it is purely pagefile access? And is a figure like 100 high? I think it reflects 100kb so is tiny, and probably not significant. Thanks James