On Wed, Jun 06, 2012 at 08:14:08AM -0400, Vivek Goyal wrote: [..] > I think it is happening because sync_file_range() will send all > the writes as SYNC and it will compete with firefox IO. On the other > hand, flusher's IO will show up as ASYNC and CFQ will be penalize it > heavily and firefox's IO will be prioritized. And this effect should > just get worse as more processes do sync_file_range(). Ok, this time I tried the same test again but with 4 processes doing writes in parallel on 4 different files. And with sync_file_range() things turned ugly. Interactivity was very poor. firefox launch test took around 1m:45s with sync_file range() while it took only about 35seconds with regular flusher threads. So sending writeback IO synchronously wreaks havoc. Thanks Vivek -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>