Hello, while struggling about an application beeing so slow on my SSD and having high I/O Waits while the app is using the raw block device i've detected that this is caused by open the block device with O_DSYNC. I've used dd and fio with oflags=direct,dsync / --direct=1 and --sync=1 and got these "strange" results: fio --sync=1: WRITE: io=1694.0MB, aggrb=57806KB/s, minb=57806KB/s, maxb=57806KB/s, mint=30008msec, maxt=30008msec fio --sync=0: WRITE: io=5978.0MB, aggrb=204021KB/s, minb=204021KB/s, maxb=204021KB/s, mint=30004msec, maxt=30004msec I get the same results on a crucial m4 as on my intel 530 ssd. I also tried the same under FreeBSD 9.1 which shows around the same results for sync=0 as sync=1: sync=0: WRITE: io=5984.0MB, aggrb=204185KB/s, minb=204185KB/s, maxb=204185KB/s, mint=30010msec, maxt=30010msec sync=1: WRITE: io=5843.0MB, aggrb=199414KB/s, minb=199414KB/s, maxb=199414KB/s, mint=30004msec, maxt=30004msec Can anyone explain to me why O_DSYNC for my app on linux is so slow? used kernel is vanilla 3.10.19 Thanks! Greets Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
