On Tue, Oct 30, 2012 at 09:01:22AM +1100, Dave Chinner wrote: > On Fri, Oct 26, 2012 at 03:19:09AM -0700, Darrick J. Wong wrote: > > Hi everyone, > > > > Are people still annoyed about writes taking unexpectedly long amounts of tme > > due to the stable page write patchset? I'm guessing yes... > > I haven't heard anyone except th elunatic fringe complain > recently... We are currently carrying a patch in the Google kernel which unconditionally disables stable page writes specifically because it introduced significant latencies that were unacceptable for some of our (internal) customers of said production kernel. I'll leave it to others to decide whether the Google production kernel is part of the lunatic fringe or not. :-) I would certainly welcome some option which allows the stable page writes to be selectively enabled or disabled. I think it would be better to only take the performance hit if the underyling hardware requires it (i.e., for iSCSI, or for DIF/DIX) or some other part of the storage stack (whether it be the file system or the dm layer), but if people want to make it a mount option, I could with that. I suspect disabling stable writes via a mount option or sysfs tunable would be much more error prone, and hence much more of a support issue for the enterprise distributions, however. So if it is done via tunable, the kernel should warn, loudly, if it's an configuration that will lead to problems (i.e., because btrfs wants to do data checksumming, or because it's required by iSCSI, or whatever). Otherwise it's going to be a support nightmare. IMO, it would be better to have the system automatically do the right thing, though. If there is no need for stable page writes, why pay the performance penalty for it? - Ted -- 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
