On Wed, Sep 27, 2017 at 09:48:35AM +0200, Michal Hocko wrote: > On Wed 27-09-17 14:04:01, Minchan Kim wrote: > > On Tue, Sep 26, 2017 at 03:21:29PM +0200, Michal Hocko wrote: > > > On Thu 21-09-17 09:33:10, Huang, Ying wrote: > > > > From: Huang Ying <ying.huang@xxxxxxxxx> > > > > > > > > This patch adds a new Kconfig option VMA_SWAP_READAHEAD and wraps VMA > > > > based swap readahead code inside #ifdef CONFIG_VMA_SWAP_READAHEAD/#endif. > > > > This is more friendly for tiny kernels. > > > > > > How (much)? > > > > > > > And as pointed to by Minchan > > > > Kim, give people who want to disable the swap readahead an opportunity > > > > to notice the changes to the swap readahead algorithm and the > > > > corresponding knobs. > > > > > > Why would anyone want that? > > > > > > Please note that adding new config options make the already complicated > > > config space even more problematic so there should be a good reason to > > > add one. Please make sure your justification is clear on why this is > > > worth the future maintenance and configurability burden. > > > > The problem is users have disabled swap readahead by echo 0 > /proc/sys/ > > vm/page-cluster are regressed by this new interface /sys/kernel/mm/swap/ > > vma_ra_max_order. Because for disabling readahead completely, they should > > disable vma_ra_max_order as well as page-cluster from now on. > > > > So, goal of new config to notice new feature to admins so they can be aware > > of new konb vma_ra_max_order as well as page-cluster. > > I canont think other better idea to preventing such regression. > > > > http://lkml.kernel.org/r/%3C20170913014019.GB29422@bbox%3E > > So, how are you going to configure this when you do not know whether > zram will be used? In other words what should e.g. distribution set this > to? I have no idea. Unfortunately, it depends on them. If they want to use zram as swap, they should fix the script. Surely, I don't like it. Instead, I wanted that page-cluster zeroing disables both virtual/pysical swap readahead not to break current userspace. However, Huang doesn't liek it. If you have better idea, please suggest. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
