On Mon, 2008-10-06 at 15:46 +0530, Aneesh Kumar K.V wrote: > On Fri, Oct 03, 2008 at 03:45:55PM -0400, Chris Mason wrote: > > On Fri, 2008-10-03 at 09:43 +1000, Dave Chinner wrote: > > > On Thu, Oct 02, 2008 at 11:48:56PM +0530, Aneesh Kumar K.V wrote: > > > > On Thu, Oct 02, 2008 at 08:20:54AM -0400, Chris Mason wrote: > > > > > On Wed, 2008-10-01 at 21:52 -0700, Andrew Morton wrote: > > > > > For a 4.5GB streaming buffered write, this printk inside > > > > > ext4_da_writepage shows up 37,2429 times in /var/log/messages. > > > > > > > > > > > > > Part of that can happen due to shrink_page_list -> pageout -> writepagee > > > > call back with lots of unallocated buffer_heads(blocks). > > > > > > Quite frankly, a simple streaming buffered write should *never* > > > trigger writeback from the LRU in memory reclaim. > > > > The blktrace runs on ext4 didn't show kswapd doing any IO. It isn't > > clear if this is because ext4 did the redirty trick or if kswapd didn't > > call writepage. > > > > -chris > > This patch actually reduced the number of extents for the below test > from 564 to 171. > For my array, this patch brings the number of ext4 extents down from over 4000 to 27. The throughput reported by dd goes up from ~80MB/s to 330MB/s, which means buffered IO is going as fast as O_DIRECT. Here's the graph: http://oss.oracle.com/~mason/bugs/writeback_ordering/ext4-aneesh.png The strange metadata writeback for the uninit block groups is gone. Looking at the patch, I think the ext4_writepages code should just make its own write_cache_pages. It's pretty hard to follow the code that is there for ext4 vs the code that is there to make write_cache_pages do what ext4 expects it to. -chris -- 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
