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d7597f59d1
Patch series "mm: process/cgroup ksm support", v9.
So far KSM can only be enabled by calling madvise for memory regions. To
be able to use KSM for more workloads, KSM needs to have the ability to be
enabled / disabled at the process / cgroup level.
Use case 1:
The madvise call is not available in the programming language. An
example for this are programs with forked workloads using a garbage
collected language without pointers. In such a language madvise cannot
be made available.
In addition the addresses of objects get moved around as they are
garbage collected. KSM sharing needs to be enabled "from the outside"
for these type of workloads.
Use case 2:
The same interpreter can also be used for workloads where KSM brings
no benefit or even has overhead. We'd like to be able to enable KSM on
a workload by workload basis.
Use case 3:
With the madvise call sharing opportunities are only enabled for the
current process: it is a workload-local decision. A considerable number
of sharing opportunities may exist across multiple workloads or jobs (if
they are part of the same security domain). Only a higler level entity
like a job scheduler or container can know for certain if its running
one or more instances of a job. That job scheduler however doesn't have
the necessary internal workload knowledge to make targeted madvise
calls.
Security concerns:
In previous discussions security concerns have been brought up. The
problem is that an individual workload does not have the knowledge about
what else is running on a machine. Therefore it has to be very
conservative in what memory areas can be shared or not. However, if the
system is dedicated to running multiple jobs within the same security
domain, its the job scheduler that has the knowledge that sharing can be
safely enabled and is even desirable.
Performance:
Experiments with using UKSM have shown a capacity increase of around 20%.
Here are the metrics from an instagram workload (taken from a machine
with 64GB main memory):
full_scans: 445
general_profit: 20158298048
max_page_sharing: 256
merge_across_nodes: 1
pages_shared: 129547
pages_sharing: 5119146
pages_to_scan: 4000
pages_unshared: 1760924
pages_volatile: 10761341
run: 1
sleep_millisecs: 20
stable_node_chains: 167
stable_node_chains_prune_millisecs: 2000
stable_node_dups: 2751
use_zero_pages: 0
zero_pages_sharing: 0
After the service is running for 30 minutes to an hour, 4 to 5 million
shared pages are common for this workload when using KSM.
Detailed changes:
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.
3. 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.
4. Add more metrics to ksm_stat
This adds the process profit metric to /proc/<pid>/ksm_stat.
5. Add more tests to ksm_tests and ksm_functional_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 two new tests to ksm_functional_tests: one to test
the new prctl options and the other one is a fork test to verify that
the KSM process setting is inherited by client processes.
This patch (of 3):
So far KSM can only be enabled by calling madvise for memory regions. To
be able to use KSM for more workloads, KSM needs to have the ability to be
enabled / disabled at the process / cgroup level.
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.
1) Introduce new MMF_VM_MERGE_ANY flag
This introduces the new flag MMF_VM_MERGE_ANY flag. When this flag
is set, kernel samepage merging (ksm) gets enabled for all vma's of a
process.
2) Setting VM_MERGEABLE on VMA creation
When a VMA is created, if the MMF_VM_MERGE_ANY flag is set, the
VM_MERGEABLE flag will be set for this VMA.
3) support disabling of ksm for a process
This adds the ability to disable ksm for a process if ksm has been
enabled for the process with prctl.
4) add new prctl option to get and set ksm for a process
This adds two new options to the prctl system call
- enable ksm for all vmas of a process (if the vmas support it).
- query if ksm has been enabled for a process.
3. Disabling MMF_VM_MERGE_ANY for storage keys in s390
In the s390 architecture when storage keys are used, the
MMF_VM_MERGE_ANY will be disabled.
Link: https://lkml.kernel.org/r/20230418051342.1919757-1-shr@devkernel.io
Link: https://lkml.kernel.org/r/20230418051342.1919757-2-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
94 lines
3.2 KiB
C
94 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_SCHED_COREDUMP_H
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#define _LINUX_SCHED_COREDUMP_H
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#include <linux/mm_types.h>
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#define SUID_DUMP_DISABLE 0 /* No setuid dumping */
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#define SUID_DUMP_USER 1 /* Dump as user of process */
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#define SUID_DUMP_ROOT 2 /* Dump as root */
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/* mm flags */
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/* for SUID_DUMP_* above */
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#define MMF_DUMPABLE_BITS 2
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#define MMF_DUMPABLE_MASK ((1 << MMF_DUMPABLE_BITS) - 1)
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extern void set_dumpable(struct mm_struct *mm, int value);
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/*
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* This returns the actual value of the suid_dumpable flag. For things
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* that are using this for checking for privilege transitions, it must
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* test against SUID_DUMP_USER rather than treating it as a boolean
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* value.
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*/
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static inline int __get_dumpable(unsigned long mm_flags)
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{
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return mm_flags & MMF_DUMPABLE_MASK;
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}
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static inline int get_dumpable(struct mm_struct *mm)
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{
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return __get_dumpable(mm->flags);
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}
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/* coredump filter bits */
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#define MMF_DUMP_ANON_PRIVATE 2
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#define MMF_DUMP_ANON_SHARED 3
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#define MMF_DUMP_MAPPED_PRIVATE 4
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#define MMF_DUMP_MAPPED_SHARED 5
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#define MMF_DUMP_ELF_HEADERS 6
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#define MMF_DUMP_HUGETLB_PRIVATE 7
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#define MMF_DUMP_HUGETLB_SHARED 8
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#define MMF_DUMP_DAX_PRIVATE 9
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#define MMF_DUMP_DAX_SHARED 10
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#define MMF_DUMP_FILTER_SHIFT MMF_DUMPABLE_BITS
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#define MMF_DUMP_FILTER_BITS 9
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#define MMF_DUMP_FILTER_MASK \
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(((1 << MMF_DUMP_FILTER_BITS) - 1) << MMF_DUMP_FILTER_SHIFT)
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#define MMF_DUMP_FILTER_DEFAULT \
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((1 << MMF_DUMP_ANON_PRIVATE) | (1 << MMF_DUMP_ANON_SHARED) |\
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(1 << MMF_DUMP_HUGETLB_PRIVATE) | MMF_DUMP_MASK_DEFAULT_ELF)
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#ifdef CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS
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# define MMF_DUMP_MASK_DEFAULT_ELF (1 << MMF_DUMP_ELF_HEADERS)
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#else
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# define MMF_DUMP_MASK_DEFAULT_ELF 0
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#endif
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/* leave room for more dump flags */
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#define MMF_VM_MERGEABLE 16 /* KSM may merge identical pages */
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#define MMF_VM_HUGEPAGE 17 /* set when mm is available for
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khugepaged */
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/*
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* This one-shot flag is dropped due to necessity of changing exe once again
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* on NFS restore
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*/
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//#define MMF_EXE_FILE_CHANGED 18 /* see prctl_set_mm_exe_file() */
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#define MMF_HAS_UPROBES 19 /* has uprobes */
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#define MMF_RECALC_UPROBES 20 /* MMF_HAS_UPROBES can be wrong */
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#define MMF_OOM_SKIP 21 /* mm is of no interest for the OOM killer */
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#define MMF_UNSTABLE 22 /* mm is unstable for copy_from_user */
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#define MMF_HUGE_ZERO_PAGE 23 /* mm has ever used the global huge zero page */
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#define MMF_DISABLE_THP 24 /* disable THP for all VMAs */
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#define MMF_OOM_REAP_QUEUED 25 /* mm was queued for oom_reaper */
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#define MMF_MULTIPROCESS 26 /* mm is shared between processes */
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/*
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* MMF_HAS_PINNED: Whether this mm has pinned any pages. This can be either
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* replaced in the future by mm.pinned_vm when it becomes stable, or grow into
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* a counter on its own. We're aggresive on this bit for now: even if the
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* pinned pages were unpinned later on, we'll still keep this bit set for the
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* lifecycle of this mm, just for simplicity.
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*/
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#define MMF_HAS_PINNED 27 /* FOLL_PIN has run, never cleared */
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#define MMF_HAS_MDWE 28
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#define MMF_HAS_MDWE_MASK (1 << MMF_HAS_MDWE)
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#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
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#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
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MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK)
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#define MMF_VM_MERGE_ANY 29
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#endif /* _LINUX_SCHED_COREDUMP_H */
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