On Tue, 27 Nov 2018 14:54:27 +0900 Minchan Kim <minc...@kernel.org> wrote:
> This patch supports new feature "zram idle/huge page writeback". > On zram-swap usecase, zram has usually many idle/huge swap pages. > It's pointless to keep in memory(ie, zram). > > To solve the problem, this feature introduces idle/huge page > writeback to backing device so the goal is to save more memory > space on embedded system. > > Normal sequence to use idle/huge page writeback feature is as follows, > > while (1) { > # mark allocated zram slot to idle > echo all > /sys/block/zram0/idle > # leave system working for several hours > # Unless there is no access for some blocks on zram, > # they are still IDLE marked pages. > > echo "idle" > /sys/block/zram0/writeback > or/and > echo "huge" > /sys/block/zram0/writeback > # write the IDLE or/and huge marked slot into backing device > # and free the memory. > } > > By per discussion: > https://lore.kernel.org/lkml/20181122065926.GG3441@jagdpanzerIV/T/#u, > > This patch removes direct incommpressibe page writeback feature > (d2afd25114f4, zram: write incompressible pages to backing device) > so we could regard it as regression because incompressible pages > doesn't go to backing storage automatically. Instead, usre should > do it via "echo huge" > /sys/block/zram/writeback" manually. I'm not in any position to determine the regression risk here. Why is that feature being removed, anyway? > If we hear some regression, we could restore the function. Why not do that now?