On Sun, Jun 06, 2010 at 12:08:19PM +0800, Wu Fengguang wrote: > On Sat, Jun 05, 2010 at 11:14:47AM +1000, Nick Piggin wrote: > > On Fri, Jun 04, 2010 at 08:47:09PM +0200, Jan Kara wrote: > > > > > > Hi, > > > > > > I've revived my patches to implement livelock avoidance for data integrity > > > writes. Due to some concerns whether tagging of pages before writeout cannot > > > be too costly to use for WB_SYNC_NONE mode (where we stop after nr_to_write > > > pages) I've changed the patch to use page tagging only in WB_SYNC_ALL mode > > > where we are sure that we write out all the tagged pages. Later, we can think > > > about using tagging for livelock avoidance for WB_SYNC_NONE mode as well... > > > > Hmm what concerns? Do you have any numbers? > > sync() is performed in two stages: the WB_SYNC_NONE run and the > WB_SYNC_ALL run. The WB_SYNC_NONE stage can still be livelocked. By concerns, I mean Jan's _performance_ concerns. I would prefer to minimise them, and then try to get an idea of the performance impact of doing tagging unconditionally. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>