Hi, Emil, On Wed, 24 Jun 2020 at 20:30, Emil Muratov <g...@hotplug.ru> wrote: > > zram swap discard is enabled by default, no need to specify additional > option. Pls, check for example info output in > https://github.com/openwrt/openwrt/pull/1515
Unfortunately, that's not quite right. This has nothing to do with zram itself, but with the way swapon syscall works. Yes, both discard *policies* are enabled by default if, *and only if* the syscall is invoked with *only* the SWAP_FLAG_DISCARD flag set [1]. Anyway, it's easy to see if the swap device is issuing trim/discard commands. For example, on my router, with my patch: root@heimdal:~# dmesg | grep swap [ 12.302928] Adding 1036284k swap on /dev/zram0. Priority:-2 extents:1 across:1036284k SSDsc root@heimdal:~# According to the relevant section of the kernel source code [2], The last letters, SSDsc mean: SS: solid state (obviously, it's a RAM-based device) D: supports discard s: area-based discard is enabled c: page-based discard is enabled Consequently, if a system only shows SS, discard commands aren't being issued. [1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/linux/swap.h?h=linux-4.14.y#n24 [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/swapfile.c?h=linux-4.14.y#n3283 Cheers, Rui _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org http://lists.infradead.org/mailman/listinfo/openwrt-devel
