I've got a workload that is latency sensitive that writes data to a memory mapped file on XFS. With the 3.0 kernel I'm seeing stalls of up to 100ms that occur during writeback that we did not see with older kernels. I've traced the stalls and it looks like they are blocking on wait_on_page_writeback() introduced in d76ee18a8551e33ad7dbd55cac38bc7b094f3abb "fs: block_page_mkwrite should wait for writeback to finish" Reading the commit description doesn't really explain to me why this change was needed. Can someone explain what "This is needed to stabilize pages during writeback for those two filesystems." means in the context of that commit? Is this a problem for older kernels as well? Should this have been backported to the stable kernels? What are the downsides of reverting this commit? Assuming this change is required are there any alternatives solutions to avoid these stalls with mmaped I/O on XFS? Thanks, Shawn --------------------------------------------------------------- This email, along with any attachments, is confidential. If you believe you received this message in error, please contact the sender immediately and delete all copies of the message. Thank you. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
