> Greetings! > > data=ordered mode has proven reliable over the years, and it does this by > ordering filedata flushes before metadata flushes. But this sometimes > causes contention in the order of a 10x slowdown for certain apps, either > due to the misuse of fsync or due to inherent behaviour like db's, as well > as inherent starvation issues exposed by the data=ordered mode. > > data=writeback mode alleviates data=order mode slowdowns, but only works > per-mount and is too dangerous to run as a default mode. > > This RFC proposes to introduce a tunable which allows to disable fsync and > changes ordered into writeback writeout on a per-process basis like this: > > echo 1 > /proc/`pidof process`/softsync I guess disabling fsync() was already commented on enough. Regarding switching to writeback mode on per-process basis - not easily possible because sometimes data is not written out by the process which stored them (think of mmaped file). And in case of DB, they use direct-io anyway most of the time so they don't care about journaling mode anyway. But as Diego wrote, there is definitely some room for improvement in current data=ordered mode so the difference shouldn't be as big in the end. Honza -- Jan Kara <jack@xxxxxxx> SuSE CR Labs - 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
