On Mon, Oct 18, 2010 at 03:49:36PM -0700, Darrick J. Wong wrote: > Through this table, I'm looking for a performance characteristic that typifies > storage with a battery-backed write cache (BBWC). As we can see from > lldd_flush_rtt_avg, the BBWC storage features a very low flush time, about 1ms > or less. Everything else, including SSDs, are over that amount. The other odd > result I see is that it takes a significant amount of time to get a flush > command from the top of the block layer to the LLDD, though I suspect some of > that might be waiting for the device to process earlier writes. Christoph has > a patch that looks like it streamlines that, but it triggered various BUG_ONs > when I booted with it, so I took the patch out. We currently synchronize flush requests. There's no real reason to do it except that we'll either need to make drivers accept flush requests with a bio attached to them or find a workaround in the block layer to submit it without bio without synchronizing them. I thin kthat should be the first angle of attack before adding complexity to filesystems. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
