Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 24 Jan 2023 17:38:39 +0100 | From | David Hildenbrand <> | Subject | Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support |
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On 23.01.23 18:37, Stefan Roesch wrote: > So far KSM can only be enabled by calling madvise for memory regions. What is > required to enable KSM for more workloads is to enable / disable it at the > process / cgroup level.
Did you stumble over the proposals from last year to enable this per-process [1] and system-wide [2]? I remember there was also regarding enabling it system-wide.
I'm going to point out the security aspect, and that e.g., Windows used to enable it system-wide before getting taught by security experts otherwise. Details on KSM and security aspects can be found in that thread.
Long story short: one has to be very careful with that and only enable it for very carefully selected worklads. Letting a workload opt-in on a VMA level is most probably safer than an admin blindly turning this on for random processes ...
Last attempts got nacked ...
[1] https://lore.kernel.org/all/20220517092701.1662641-1-xu.xin16@zte.com.cn/ [2] https://lore.kernel.org/all/20220609055658.703472-1-xu.xin16@zte.com.cn/
> > 1. New options for prctl system command > This patch series adds two new options to the prctl system call. The first > one allows to enable KSM at the process level and the second one to query the > setting. > > The setting will be inherited by child processes. > > With the above setting, KSM can be enabled for the seed process of a cgroup > and all processes in the cgroup will inherit the setting. > > 2. Changes to KSM processing > When KSM is enabled at the process level, the KSM code will iterate over all > the VMA's and enable KSM for the eligible VMA's. > > When forking a process that has KSM enabled, the setting will be inherited by > the new child process. > > In addition when KSM is disabled for a process, KSM will be disabled for the > VMA's where KSM has been enabled. > > 3. Add tracepoints to KSM > Currently KSM has no tracepoints. This adds tracepoints to the key KSM functions > to make it easier to debug KSM. > > 4. Add general_profit metric > The general_profit metric of KSM is specified in the documentation, but not > calculated. This adds the general profit metric to /sys/kernel/debug/mm/ksm. > > 5. Add more metrics to ksm_stat > This adds the process profit and ksm type metric to /proc/<pid>/ksm_stat. > > 6. Add more tests to ksm_tests > This adds an option to specify the merge type to the ksm_tests. This allows to > test madvise and prctl KSM. It also adds a new option to query if prctl KSM has > been enabled. It adds a fork test to verify that the KSM process setting is > inherited by client processes. > > > Stefan Roesch (20): > mm: add new flag to enable ksm per process > mm: add flag to __ksm_enter > mm: add flag to __ksm_exit call > mm: invoke madvise for all vmas in scan_get_next_rmap_item > mm: support disabling of ksm for a process > mm: add new prctl option to get and set ksm for a process > mm: add tracepoints to ksm > mm: split off pages_volatile function > mm: expose general_profit metric > docs: document general_profit sysfs knob > mm: calculate ksm process profit metric > mm: add ksm_merge_type() function > mm: expose ksm process profit metric in ksm_stat > mm: expose ksm merge type in ksm_stat > docs: document new procfs ksm knobs > tools: add new prctl flags to prctl in tools dir > selftests/vm: add KSM prctl merge test > selftests/vm: add KSM get merge type test > selftests/vm: add KSM fork test > selftests/vm: add two functions for debugging merge outcome > > Documentation/ABI/testing/sysfs-kernel-mm-ksm | 8 + > Documentation/admin-guide/mm/ksm.rst | 8 +- > MAINTAINERS | 1 + > fs/proc/base.c | 5 + > include/linux/ksm.h | 19 +- > include/linux/sched/coredump.h | 1 + > include/trace/events/ksm.h | 257 ++++++++++++++++++ > include/uapi/linux/prctl.h | 2 + > kernel/sys.c | 29 ++ > mm/ksm.c | 134 ++++++++- > tools/include/uapi/linux/prctl.h | 2 + > tools/testing/selftests/vm/Makefile | 3 +- > tools/testing/selftests/vm/ksm_tests.c | 254 ++++++++++++++--- > 13 files changed, 665 insertions(+), 58 deletions(-) > create mode 100644 include/trace/events/ksm.h > > > base-commit: c1649ec55708ae42091a2f1bca1ab49ecd722d55
-- Thanks,
David / dhildenb
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