[Forgot Hugh] On Tue 14-05-19 16:41:05, Michal Hocko wrote: > [This is adding a new user visible interface so you should be CCing > linux-api mailing list. Also CC Hugh for KSM in general. Done now] > > On Tue 14-05-19 15:16:50, Oleksandr Natalenko wrote: > > By default, KSM works only on memory that is marked by madvise(). And the > > only way to get around that is to either: > > > > * use LD_PRELOAD; or > > * patch the kernel with something like UKSM or PKSM. > > > > Instead, lets implement a sysfs knob, which allows marking VMAs as > > mergeable. This can be used manually on some task in question or by some > > small userspace helper daemon. > > > > The knob is named "force_madvise", and it is write-only. It accepts a PID > > to act on. To mark the VMAs as mergeable, use: > > > > # echo PID > /sys/kernel/mm/ksm/force_madvise > > > > To unmerge all the VMAs, use the same approach, prepending the PID with > > the "minus" sign: > > > > # echo -PID > /sys/kernel/mm/ksm/force_madvise > > > > This patchset is based on earlier Timofey's submission [1], but it doesn't > > use dedicated kthread to walk through the list of tasks/VMAs. Instead, > > it is up to userspace to traverse all the tasks in /proc if needed. > > > > The previous suggestion [2] was based on amending do_anonymous_page() > > handler to implement fully automatic mode, but this approach was > > incorrect due to improper locking and not desired due to excessive > > complexity. > > > > The current approach just implements minimal interface and leaves the > > decision on how and when to act to userspace. > > Please make sure to describe a usecase that warrants adding a new > interface we have to maintain for ever. > > > > > Thanks. > > > > [1] https://lore.kernel.org/patchwork/patch/1012142/ > > [2] http://lkml.iu.edu/hypermail/linux/kernel/1905.1/02417.html > > > > Oleksandr Natalenko (4): > > mm/ksm: introduce ksm_enter() helper > > mm/ksm: introduce ksm_leave() helper > > mm/ksm: introduce force_madvise knob > > mm/ksm: add force merging/unmerging documentation > > > > Documentation/admin-guide/mm/ksm.rst | 11 ++ > > mm/ksm.c | 160 +++++++++++++++++++++------ > > 2 files changed, 137 insertions(+), 34 deletions(-) > > > > -- > > 2.21.0 > > > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs
