On Thu, Sep 15, 2011 at 09:47:55AM -0500, Shawn Bohrer wrote: > 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. It it there to avoid pages beeing modified while they are under writeback, which defeats various checksumming like DIF/DIX, the iscsi CRCs, or even just the RAID parity calculations. All of these either failed before, or had to work around it by copying all data was written. If you don't use any of these you can remove the call and things will work like they did before. -- 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
