On Mon, 6 Apr 2009 23:21:41 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > I mean, let's graph it: > > WRITE_SYNC -> WRITE_SYNC_PLUG -> BIO_RW_SYNCIO -> bio_sync() -> REQ_RW_SYNC -> rw_is_sync() -> does something mysterious in get_request() > -> rq_is_sync() -> does something mysterious in IO schedulers > -> BIO_RW_NOIDLE -> bio_noidle() -> REQ_NOIDLE -> rq_noidle() -> does something mysterious in cfq-iosched only > -> BIO_RW_UNPLUG -> bio_unplug() -> REQ_UNPLUG -> OK, the cognoscenti know what this is supposed to do, but it is unused! whoop, I found a use of bio_unplug() in __make_request(). So it appears that the intent of your patch is to cause an unplug after submission of each WB_SYNC_ALL block? But what about all the other stuff which WRITE_SYNC might or might not do? What does WRITE_SYNC _actually_ do, and what are the actual effects of this change?? And what effect will this large stream of unplugs have upon merging? -- 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
