Hello, the output of the cache calibrator indicated, that TLB misses on the MPC 860 might influence latencies substantially. Looking closer to the Linux 2.6 kernel revealed, that TLB entries for the kernel space (0xc0000000) are not pinned by default for the MPC 860 (like in 2.4). I enabled this advanced kernel option PIN_TLB and furthermore patched the kernel to put modules in that kernel space by using kmalloc instead of vmalloc. Then I get the following latency figures:
KLATENCY with load: RTH|---lat min|---lat avg|---lat max|-overrun|--lat best|---lat worst RTS| 50560| 98976| 199040| 0| 00:09:45 RTS| 50240| 89401| 174400| 0| 00:10:06 PIN_TLB RTS| 48960| 85562| 164480| 0| 00:10:30 PIN_TLB+kmalloc LATENCY with load: RTH|---lat min|---lat avg|---lat max|-overrun|--lat best|---lat worst RTS| 60480| 120960| 224320| 0| 00:09:46 RTS| 60800| 105600| 193600| 0| 00:09:56 PIN_TLB RTS| 55680| 98240| 176640| 0| 00:15:01 PIN_TLB+kmalloc This clearly shows, that TLB misses are one latency killer on low end processors. Wolfgang.
