MySQL Forums :: Performance :: 64bit mysql is slower than 32bit?

in my test,
I found 64 bit mysql is slower than 32 bit
the problem maybe is caused by IO
because I found my 64bit linux which runs the 64bit mysql vmstat is like this:
procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 1 160 45188 91520 2880428 0 0 594 2970 2774 3515 4 1 55 39 0
1 0 160 46908 91516 2879404 0 0 228 282 2763 3478 5 1 67 27 0
0 0 160 45004 91536 2881440 0 0 324 454 2942 3385 5 1 78 16 0
0 0 160 46592 91492 2879428 0 0 220 174 2898 3564 6 1 84 9 0
0 1 160 45488 91512 2879408 0 0 198 394 2898 3573 6 1 81 12 0
0 0 160 47388 91504 2877360 0 0 258 158 2953 3562 6 1 85 8 0
1 0 160 45732 91524 2877340 0 0 252 382 2912 3601 7 1 80 12 0
0 1 160 47132 91520 2877344 0 0 276 392 2919 3693 7 2 85 6 0
0 0 160 45476 91544 2877320 0 0 258 336 2880 3773 9 2 71 17 0
0 1 160 44308 91564 2879356 0 0 188 476 2844 3829 8 2 78 12 0
0 0 160 45592 91548 2876288 0 0 292 172 2775 4001 6 2 83 9 0
3 0 160 44484 91568 2877296 0 0 182 320 2967 3508 5 2 86 7 0
0 5 160 45580 91560 2874220 0 0 276 352 2986 3246 5 2 84 10 0
1 0 160 44416 91568 2876268 0 0 194 176 2994 3171 5 2 85 9 0
0 1 160 46892 91512 2872212 0 0 230 332 2966 3211 3 2 84 11 0
0 7 160 46992 91552 2871144 0 0 226 2290 2829 3190 4 2 63 31 0
0 4 160 45516 91608 2873144 0 0 240 1120 2691 3080 3 1 56 39 0
1 0 160 45464 91592 2872132 0 0 570 278 3059 3122 3 1 87 8 0
0 0 160 47236 91552 2869088 0 0 238 392 3068 3185 2 1 89 9 0
0 0 160 46440 91568 2870100 0 0 156 260 2895 3219 5 1 88 6 0
0 0 160 45212 91584 2871112 0 0 170 282 3021 3098 4 1 86 8 0


but 32bit is like this:
procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 168 209772 378456 6603720 0 0 0 4156 3052 2925 2 1 97 0 0
0 0 168 209772 378456 6603720 0 0 0 4678 3073 2932 2 1 96 0 0
0 0 168 209648 378456 6604748 0 0 0 4114 3079 2935 2 1 96 0 0
0 0 168 209288 378460 6604744 0 0 0 4186 3065 2951 1 1 98 0 0
3 0 168 209288 378460 6604744 0 0 0 4230 2959 2908 1 1 98 0 0
0 0 168 209288 378460 6604744 0 0 0 2214 2777 2986 2 1 97 0 0
0 0 168 209384 378460 6604744 0 0 0 4344 2964 2983 2 0 97 0 0
0 0 168 209260 378460 6604744 0 0 0 4120 3022 2942 2 1 97 0 0
1 2 168 209104 378460 6604744 0 0 0 4254 2985 2955 2 1 97 0 0
0 0 168 209104 378464 6604740 0 0 0 4220 3075 3066 2 1 97 0 0
0 0 168 209068 378464 6604740 0 0 0 2120 2835 2968 2 1 97 0 0
0 0 168 209068 378464 6604740 0 0 0 4398 3105 3085 3 1 96 0 0
0 0 168 208944 378464 6604740 0 0 0 4196 3091 3074 3 1 96 0 0
0 0 168 208880 378464 6604740 0 0 0 4326 3072 2969 4 1 95 0 0
0 0 168 208756 378464 6604740 0 0 0 4218 3005 2970 3 1 95 0 0
0 0 168 208756 378464 6604740 0 0 0 2132 2833 2973 4 1 95 0 0
0 0 168 208696 378468 6604736 0 0 0 4592 3001 3107 5 1 94 0 0


can anyone help find why the IO problem is caused?