On Sun, 1 Dec 2013, James Harper wrote: > 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.
100 is indeed 100kB/s, and is tiny. drives capable of 70 or so IOPs seem to be able to get about 3000kB (and it's been annoyingly at this level for a decade or so for me). You would almost expect "swap in" to include mmapped data, wouldn't you - it's the same part of the kernel surely? But in this case, unless you're also calling msync() (apt-get does - and there's a current open bug against zfs because msync is pessimistically crap currently, but there is a patch in the works), then the rates for mmap can't possibly be that low. 70-90MByte/s is about as good as you'll get in real life on everything but SAN hardware with 8gbps fibrechannel. -- Tim Connors _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
