Fajun Chen wrote:
Hi All, I use sg/libata and ata pass through for read/writes. Linux 2.6.18-rc2 and libata version 2.00 are loaded on ARM XScale board. Under heavy cpu load (e.g. when blocks per transfer/sector count is set to 1), I've observed that the test application can suck cpu away for long time (more than 20 seconds) and other processes including high priority shell can not get the time slice to run. What's interesting is that if the application is under heavy IO load (e.g. when blocks per transfer/sector count is set to 256), the problem goes away. I also tested with open source code sg_utils and got the same result, so this is not a problem specific to my user-space application.
.. Post the relevant code here, and then we'll be able to better understand and explain it to you. For example, if the code is using ATA opcodes 0x20, 0x21, 0x24, 0x30, 0x31, 0x34, 0x29, 0x39, 0xc4 or 0xc5 (any of the R/W PIO ops), then this behaviour does not surprise me in the least. Fully expected and difficult to avoid. Cheers - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
