On Wed, Oct 19, 2011 at 6:15 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Wed, Oct 19, 2011 at 6:02 PM, Andreas Dilger <adilger@xxxxxxxxx> wrote: >> What kernel are you using? A change to keep pages consistent during writeout was landed not too long ago (maybe Linux 3.0) in order to allow checksumming of the data. > > 3.0.6, with no relevant patches. (I have a one-liner added to the tcp > code that I'll submit sometime soon.) Would this explain the latency > in file_update_time or is that a separate issue? file_update_time > seems like a good thing to make fully asynchronous (especially if the > file in question is a fifo, but I've already moved my fifos to tmpfs). On 2.6.39.4, I got one instance of: call_rwsem_down_read_failed ext4_map_blocks ext4_da_get_block_prep __block_write_begin ext4_da_write_begin ext4_page_mkwrite do_wp_page handle_pte_fault handle_mm_fault do_page_fault page_fault but I'm not seeing the large numbers of the ext4_page_mkwrite trace that I get on 3.0.6. file_update_time is now by far the dominant cause of latency. I'll leave it running overnight and see what happens. --Andy -- 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
