Dear All, I could see serious time latency with disk cache flush. Usually it takes about 2-10 s to flush disk cache with a SCSI disk.I have tested this with ide disk controller, and could not see big latency compared to scsi. This is the scenario; 1. using cp command; copying of large (500MB) file set in background. Continuously copying. 2. Using my own small programme, i am writing 50 bytes of data blocks to same disk PARTITION for 60 - 200 seconds. Usually it takes less than 1ms to return write() method. But in that loop, there could be one or more write() method instances which would take around 2-15s for return. Exceptions: If I use direct copy "cp", instead of standard "cp". Result is normal. If i use different partitions for two operations. Result is normal. I have tried with three I/O schedulers and preemtible kernel options. But no luck. Up to my knowledge I hope, that 1-15s are taken for Disk Cache flush or some thing in kernel space. Can there be such latency in disk write in SCSI or in Linux disk caching. Thank You! Best regards, Tharindu R -- Tharindu Rukshan Bamunuarachchi all fabrications are subject to decay - : 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
