Hi, I am confused about the numbers regarding CPU utilization I got lately on a RAID or JBOD. With linux 2.4.18 kernel, Intel motherboard, 4 IBM DTLA 7200rpm disk connected to system through Promise Ultra100 card. I used vmstat to get CPU utilization. It is quite high. One testing program open a raw device and sequentially read 64k chunk from it. I got 40% CPU utilization by sequential read one ide disk at 64K size. The throughput is about 37 MB/sec. 100% when accessing four disk as JBOD, i.e., four testing program accessing four disk separately. 40% when accessing these 4 drives as one RAID-5 disk array. It is just too high. Similar high numbers of CPU utilziation can be seen from others' tests like http://www.nobell.org/~gjm/linux/ide-raid/ What does the kernel do then? DMA is on. Is it memcpy? call back funtions? I don't think it is memcpy, as I simulate the amount of bytes to be memcpyed in use-level, it takes less than 5% CPU. Thanks, Lan - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
