user/sven/linux.git/kernel/cgroup/cpuset.c, branch v5.2.7

cpuset: restore sanity to cpuset_cpus_allowed_fallback()

2019-06-12T18:00:08Z

In the case that a process is constrained by taskset(1) (i.e. sched_setaffinity(2)) to a subset of available cpus, and all of those are subsequently offlined, the scheduler will set tsk->cpus_allowed to the current value of task_cs(tsk)->effective_cpus. This is done via a call to do_set_cpus_allowed() in the context of cpuset_cpus_allowed_fallback() made by the scheduler when this case is detected. This is the only call made to cpuset_cpus_allowed_fallback() in the latest mainline kernel. However, this is not sane behavior. I will demonstrate this on a system running the latest upstream kernel with the following initial configuration: # grep -i cpu /proc/$$/status Cpus_allowed: ffffffff,fffffff Cpus_allowed_list: 0-63 (Where cpus 32-63 are provided via smt.) If we limit our current shell process to cpu2 only and then offline it and reonline it: # taskset -p 4 $$ pid 2272's current affinity mask: ffffffffffffffff pid 2272's new affinity mask: 4 # echo off > /sys/devices/system/cpu/cpu2/online # dmesg | tail -3 [ 2195.866089] process 2272 (bash) no longer affine to cpu2 [ 2195.872700] IRQ 114: no longer affine to CPU2 [ 2195.879128] smpboot: CPU 2 is now offline # echo on > /sys/devices/system/cpu/cpu2/online # dmesg | tail -1 [ 2617.043572] smpboot: Booting Node 0 Processor 2 APIC 0x4 We see that our current process now has an affinity mask containing every cpu available on the system _except_ the one we originally constrained it to: # grep -i cpu /proc/$$/status Cpus_allowed: ffffffff,fffffffb Cpus_allowed_list: 0-1,3-63 This is not sane behavior, as the scheduler can now not only place the process on previously forbidden cpus, it can't even schedule it on the cpu it was originally constrained to! Other cases result in even more exotic affinity masks. Take for instance a process with an affinity mask containing only cpus provided by smt at the moment that smt is toggled, in a configuration such as the following: # taskset -p f000000000 $$ # grep -i cpu /proc/$$/status Cpus_allowed: 000000f0,00000000 Cpus_allowed_list: 36-39 A double toggle of smt results in the following behavior: # echo off > /sys/devices/system/cpu/smt/control # echo on > /sys/devices/system/cpu/smt/control # grep -i cpus /proc/$$/status Cpus_allowed: ffffff00,ffffffff Cpus_allowed_list: 0-31,40-63 This is even less sane than the previous case, as the new affinity mask excludes all smt-provided cpus with ids less than those that were previously in the affinity mask, as well as those that were actually in the mask. With this patch applied, both of these cases end in the following state: # grep -i cpu /proc/$$/status Cpus_allowed: ffffffff,ffffffff Cpus_allowed_list: 0-63 The original policy is discarded. Though not ideal, it is the simplest way to restore sanity to this fallback case without reinventing the cpuset wheel that rolls down the kernel just fine in cgroup v2. A user who wishes for the previous affinity mask to be restored in this fallback case can use that mechanism instead. This patch modifies scheduler behavior by instead resetting the mask to task_cs(tsk)->cpus_allowed by default, and cpu_possible mask in legacy mode. I tested the cases above on both modes. Note that the scheduler uses this fallback mechanism if and only if _every_ other valid avenue has been traveled, and it is the last resort before calling BUG(). Suggested-by: Waiman Long Suggested-by: Phil Auld Signed-off-by: Joel Savitz Acked-by: Phil Auld Acked-by: Waiman Long Acked-by: Peter Zijlstra (Intel) Signed-off-by: Tejun Heo

cgroup/cpuset: Update stale generate_sched_domains() comments

2019-04-19T17:44:14Z

Commit: fc560a26acce ("cpuset: replace cpuset->stack_list with cpuset_for_each_descendant_pre()") removed the local list (q) that was used to perform a top-down scan of all cpusets; however, comments mentioning it were not updated. Update comments to reflect current implementation. Signed-off-by: Juri Lelli Acked-by: Tejun Heo Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: cgroups@vger.kernel.org Cc: lizefan@huawei.com Link: http://lkml.kernel.org/r/20181219133445.31982-1-juri.lelli@redhat.com Signed-off-by: Ingo Molnar

Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2019-03-12T21:08:19Z

Pull vfs mount infrastructure updates from Al Viro: "The rest of core infrastructure; no new syscalls in that pile, but the old parts are switched to new infrastructure. At that point conversions of individual filesystems can happen independently; some are done here (afs, cgroup, procfs, etc.), there's also a large series outside of that pile dealing with NFS (quite a bit of option-parsing stuff is getting used there - it's one of the most convoluted filesystems in terms of mount-related logics), but NFS bits are the next cycle fodder. It got seriously simplified since the last cycle; documentation is probably the weakest bit at the moment - I considered dropping the commit introducing Documentation/filesystems/mount_api.txt (cutting the size increase by quarter ;-), but decided that it would be better to fix it up after -rc1 instead. That pile allows to do followup work in independent branches, which should make life much easier for the next cycle. fs/super.c size increase is unpleasant; there's a followup series that allows to shrink it considerably, but I decided to leave that until the next cycle" * 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (41 commits) afs: Use fs_context to pass parameters over automount afs: Add fs_context support vfs: Add some logging to the core users of the fs_context log vfs: Implement logging through fs_context vfs: Provide documentation for new mount API vfs: Remove kern_mount_data() hugetlbfs: Convert to fs_context cpuset: Use fs_context kernfs, sysfs, cgroup, intel_rdt: Support fs_context cgroup: store a reference to cgroup_ns into cgroup_fs_context cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper cgroup_do_mount(): massage calling conventions cgroup: stash cgroup_root reference into cgroup_fs_context cgroup2: switch to option-by-option parsing cgroup1: switch to option-by-option parsing cgroup: take options parsing into ->parse_monolithic() cgroup: fold cgroup1_mount() into cgroup1_get_tree() cgroup: start switching to fs_context ipc: Convert mqueue fs to fs_context proc: Add fs_context support to procfs ...

cpuset: Use fs_context

2019-02-28T08:29:35Z

Make the cpuset filesystem use the filesystem context. This is potentially tricky as the cpuset fs is almost an alias for the cgroup filesystem, but with some special parameters. This can, however, be handled by setting up an appropriate cgroup filesystem and returning the root directory of that as the root dir of this one. Signed-off-by: David Howells cc: Tejun Heo Signed-off-by: Al Viro

cpuset: remove unused task_has_mempolicy()

2019-02-19T14:26:02Z

This is a remnant of commit 5f155f27cb7f ("mm, cpuset: always use seqlock when changing task's nodemask"). Signed-off-by: Masahiro Yamada Signed-off-by: Tejun Heo

Merge branch 'for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2018-12-29T18:57:20Z

Pull cgroup updates from Tejun Heo: - Waiman's cgroup2 cpuset support has been finally merged closing one of the last remaining feature gaps. - cgroup.procs could show non-leader threads when cgroup2 threaded mode was used in certain ways. I forgot to push the fix during the last cycle. - A patch to fix mount option parsing when all mount options have been consumed by someone else (LSM). - cgroup_no_v1 boot param can now block named cgroup1 hierarchies too. * 'for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: Add named hierarchy disabling to cgroup_no_v1 boot param cgroup: fix parsing empty mount option string cpuset: Remove set but not used variable 'cs' cgroup: fix CSS_TASK_ITER_PROCS cgroup: Add .__DEBUG__. prefix to debug file names cpuset: Minor cgroup2 interface updates cpuset: Expose cpuset.cpus.subpartitions with cgroup_debug cpuset: Add documentation about the new "cpuset.sched.partition" flag cpuset: Use descriptive text when reading/writing cpuset.sched.partition cpuset: Expose cpus.effective and mems.effective on cgroup v2 root cpuset: Make generate_sched_domains() work with partition cpuset: Make CPU hotplug work with partition cpuset: Track cpusets that use parent's effective_cpus cpuset: Add an error state to cpuset.sched.partition cpuset: Add new v2 cpuset.sched.partition flag cpuset: Simply allocation and freeing of cpumasks cpuset: Define data structures to support scheduling partition cpuset: Enable cpuset controller in default hierarchy cgroup: remove unnecessary unlikely()

mm, oom: reorganize the oom report in dump_header

2018-12-28T20:11:48Z

OOM report contains several sections. The first one is the allocation context that has triggered the OOM. Then we have cpuset context followed by the stack trace of the OOM path. The tird one is the OOM memory information. Followed by the current memory state of all system tasks. At last, we will show oom eligible tasks and the information about the chosen oom victim. One thing that makes parsing more awkward than necessary is that we do not have a single and easily parsable line about the oom context. This patch is reorganizing the oom report to 1) who invoked oom and what was the allocation request [ 515.902945] tuned invoked oom-killer: gfp_mask=0x6200ca(GFP_HIGHUSER_MOVABLE), order=0, oom_score_adj=0 2) OOM stack trace [ 515.904273] CPU: 24 PID: 1809 Comm: tuned Not tainted 4.20.0-rc3+ #3 [ 515.905518] Hardware name: Inspur SA5212M4/YZMB-00370-107, BIOS 4.1.10 11/14/2016 [ 515.906821] Call Trace: [ 515.908062] dump_stack+0x5a/0x73 [ 515.909311] dump_header+0x55/0x28c [ 515.914260] oom_kill_process+0x2d8/0x300 [ 515.916708] out_of_memory+0x145/0x4a0 [ 515.917932] __alloc_pages_slowpath+0x7d2/0xa16 [ 515.919157] __alloc_pages_nodemask+0x277/0x290 [ 515.920367] filemap_fault+0x3d0/0x6c0 [ 515.921529] ? filemap_map_pages+0x2b8/0x420 [ 515.922709] ext4_filemap_fault+0x2c/0x40 [ext4] [ 515.923884] __do_fault+0x20/0x80 [ 515.925032] __handle_mm_fault+0xbc0/0xe80 [ 515.926195] handle_mm_fault+0xfa/0x210 [ 515.927357] __do_page_fault+0x233/0x4c0 [ 515.928506] do_page_fault+0x32/0x140 [ 515.929646] ? page_fault+0x8/0x30 [ 515.930770] page_fault+0x1e/0x30 3) OOM memory information [ 515.958093] Mem-Info: [ 515.959647] active_anon:26501758 inactive_anon:1179809 isolated_anon:0 active_file:4402672 inactive_file:483963 isolated_file:1344 unevictable:0 dirty:4886753 writeback:0 unstable:0 slab_reclaimable:148442 slab_unreclaimable:18741 mapped:1347 shmem:1347 pagetables:58669 bounce:0 free:88663 free_pcp:0 free_cma:0 ... 4) current memory state of all system tasks [ 516.079544] [ 744] 0 744 9211 1345 114688 82 0 systemd-journal [ 516.082034] [ 787] 0 787 31764 0 143360 92 0 lvmetad [ 516.084465] [ 792] 0 792 10930 1 110592 208 -1000 systemd-udevd [ 516.086865] [ 1199] 0 1199 13866 0 131072 112 -1000 auditd [ 516.089190] [ 1222] 0 1222 31990 1 110592 157 0 smartd [ 516.091477] [ 1225] 0 1225 4864 85 81920 43 0 irqbalance [ 516.093712] [ 1226] 0 1226 52612 0 258048 426 0 abrtd [ 516.112128] [ 1280] 0 1280 109774 55 299008 400 0 NetworkManager [ 516.113998] [ 1295] 0 1295 28817 37 69632 24 0 ksmtuned [ 516.144596] [ 10718] 0 10718 2622484 1721372 15998976 267219 0 panic [ 516.145792] [ 10719] 0 10719 2622484 1164767 9818112 53576 0 panic [ 516.146977] [ 10720] 0 10720 2622484 1174361 9904128 53709 0 panic [ 516.148163] [ 10721] 0 10721 2622484 1209070 10194944 54824 0 panic [ 516.149329] [ 10722] 0 10722 2622484 1745799 14774272 91138 0 panic 5) oom context (contrains and the chosen victim). oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0-1,task=panic,pid=10737,uid=0 An admin can easily get the full oom context at a single line which makes parsing much easier. Link: http://lkml.kernel.org/r/1542799799-36184-1-git-send-email-ufo19890607@gmail.com Signed-off-by: yuzhoujian Acked-by: Michal Hocko Cc: Andrea Arcangeli Cc: David Rientjes Cc: "Kirill A . Shutemov" Cc: Roman Gushchin Cc: Tetsuo Handa Cc: Yang Shi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cpuset: Remove set but not used variable 'cs'

2018-12-03T16:23:22Z

Fixes gcc '-Wunused-but-set-variable' warning: kernel/cgroup/cpuset.c: In function 'cpuset_cancel_attach': kernel/cgroup/cpuset.c:2167:17: warning: variable 'cs' set but not used [-Wunused-but-set-variable] It never used since introduction in commit 1f7dd3e5a6e4 ("cgroup: fix handling of multi-destination migration from subtree_control enabling") Signed-off-by: YueHaibing Signed-off-by: Tejun Heo

cpuset: Minor cgroup2 interface updates

2018-11-13T20:09:48Z

* Rename the partition file from "cpuset.sched.partition" to "cpuset.cpus.partition". * When writing to the partition file, drop "0" and "1" and only accept "member" and "root". Signed-off-by: Tejun Heo Cc: Peter Zijlstra (Intel) Cc: Waiman Long

cpuset: Expose cpuset.cpus.subpartitions with cgroup_debug

2018-11-08T20:27:32Z

For debugging purpose, it will be useful to expose the content of the subparts_cpus as a read-only file to see if the code work correctly. However, subparts_cpus will not be used at all in most use cases. So adding a new cpuset file that clutters the cgroup directory may not be desirable. This is now being done by using the hidden "cgroup_debug" kernel command line option to expose a new "cpuset.cpus.subpartitions" file. That option was originally used by the debug controller to expose itself when configured into the kernel. This is now extended to set an internal flag used by cgroup_addrm_files(). A new CFTYPE_DEBUG flag can now be used to specify that a cgroup file should only be created when the "cgroup_debug" option is specified. Signed-off-by: Waiman Long Acked-by: Peter Zijlstra (Intel) Signed-off-by: Tejun Heo