On Tue, Jul 14, 2009 at 05:02:53PM +0300, Adrian Hunter wrote: > Hi > > We are using linux 2.6.28 and we have a situation where ext3 > can take 30-60 seconds to mount. > > The cause is the underlying device has extremely poor random > write speed (several orders of magnitude slower than sequential > write speed), and journal recovery can involve many small random > writes. > > To alleviate this situation somewhat, I have two moderately ugly > hacks: > HACK 1: ext3: mount fast even when recovering > HACK 2: do I/O read requests while ext3 journal recovers > > HACK 1 uses a I/O barrier in place of waiting for recovery I/O to be > flushed. > > HACK 2 crudely throws I/O read requests to the front of the dispatch > queue until the I/O barrier from HACK 1 is reached. Have you actually benchmarked these patches, ideally with a fixed filesystem image so the two runs are done requiring exactly the same number of blocks to recover? We implement ordered I/O in terms of doing a flush, so it would be surprising to see that a significant difference in times. Also, it would be useful to do a blktrace before and after your patches, again with a fixed filesystem image so the experiment can be carefully controlled. Regards, - Ted -- 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
