| Message ID | 20241025012304.2473312-2-shakeel.butt@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | memcg-v1: fully deprecate charge moving | expand |
On Thu 24-10-24 18:22:58, Shakeel Butt wrote: > Proceed with the complete deprecation of memcg v1's charge moving > feature. The deprecation warning has been in the kernel for almost two > years and has been ported to all stable kernel since. Now is the time to > fully deprecate this feature. > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Thanks! > --- > > Changes since RFC: > - Writing 0 to memory.move_charge_at_immigrate is allowed. > > .../admin-guide/cgroup-v1/memory.rst | 82 +------------------ > mm/memcontrol-v1.c | 14 +--- > 2 files changed, 5 insertions(+), 91 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst > index 270501db9f4e..286d16fc22eb 100644 > --- a/Documentation/admin-guide/cgroup-v1/memory.rst > +++ b/Documentation/admin-guide/cgroup-v1/memory.rst > @@ -90,9 +90,7 @@ Brief summary of control files. > used. > memory.swappiness set/show swappiness parameter of vmscan > (See sysctl's vm.swappiness) > - memory.move_charge_at_immigrate set/show controls of moving charges > - This knob is deprecated and shouldn't be > - used. > + memory.move_charge_at_immigrate This knob is deprecated. > memory.oom_control set/show oom controls. > This knob is deprecated and shouldn't be > used. > @@ -243,10 +241,6 @@ behind this approach is that a cgroup that aggressively uses a shared > page will eventually get charged for it (once it is uncharged from > the cgroup that brought it in -- this will happen on memory pressure). > > -But see :ref:`section 8.2 <cgroup-v1-memory-movable-charges>` when moving a > -task to another cgroup, its pages may be recharged to the new cgroup, if > -move_charge_at_immigrate has been chosen. > - > 2.4 Swap Extension > -------------------------------------- > > @@ -756,78 +750,8 @@ If we want to change this to 1G, we can at any time use:: > > THIS IS DEPRECATED! > > -It's expensive and unreliable! It's better practice to launch workload > -tasks directly from inside their target cgroup. Use dedicated workload > -cgroups to allow fine-grained policy adjustments without having to > -move physical pages between control domains. > - > -Users can move charges associated with a task along with task migration, that > -is, uncharge task's pages from the old cgroup and charge them to the new cgroup. > -This feature is not supported in !CONFIG_MMU environments because of lack of > -page tables. > - > -8.1 Interface > -------------- > - > -This feature is disabled by default. It can be enabled (and disabled again) by > -writing to memory.move_charge_at_immigrate of the destination cgroup. > - > -If you want to enable it:: > - > - # echo (some positive value) > memory.move_charge_at_immigrate > - > -.. note:: > - Each bits of move_charge_at_immigrate has its own meaning about what type > - of charges should be moved. See :ref:`section 8.2 > - <cgroup-v1-memory-movable-charges>` for details. > - > -.. note:: > - Charges are moved only when you move mm->owner, in other words, > - a leader of a thread group. > - > -.. note:: > - If we cannot find enough space for the task in the destination cgroup, we > - try to make space by reclaiming memory. Task migration may fail if we > - cannot make enough space. > - > -.. note:: > - It can take several seconds if you move charges much. > - > -And if you want disable it again:: > - > - # echo 0 > memory.move_charge_at_immigrate > - > -.. _cgroup-v1-memory-movable-charges: > - > -8.2 Type of charges which can be moved > --------------------------------------- > - > -Each bit in move_charge_at_immigrate has its own meaning about what type of > -charges should be moved. But in any case, it must be noted that an account of > -a page or a swap can be moved only when it is charged to the task's current > -(old) memory cgroup. > - > -+---+--------------------------------------------------------------------------+ > -|bit| what type of charges would be moved ? | > -+===+==========================================================================+ > -| 0 | A charge of an anonymous page (or swap of it) used by the target task. | > -| | You must enable Swap Extension (see 2.4) to enable move of swap charges. | > -+---+--------------------------------------------------------------------------+ > -| 1 | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory) | > -| | and swaps of tmpfs file) mmapped by the target task. Unlike the case of | > -| | anonymous pages, file pages (and swaps) in the range mmapped by the task | > -| | will be moved even if the task hasn't done page fault, i.e. they might | > -| | not be the task's "RSS", but other task's "RSS" that maps the same file. | > -| | The mapcount of the page is ignored (the page can be moved independent | > -| | of the mapcount). You must enable Swap Extension (see 2.4) to | > -| | enable move of swap charges. | > -+---+--------------------------------------------------------------------------+ > - > -8.3 TODO > --------- > - > -- All of moving charge operations are done under cgroup_mutex. It's not good > - behavior to hold the mutex too long, so we may need some trick. > +Reading memory.move_charge_at_immigrate will always return 0 and writing > +to it will always return -EINVAL. > > 9. Memory thresholds > ==================== > diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c > index 81d8819f13cd..9b3b1a446c65 100644 > --- a/mm/memcontrol-v1.c > +++ b/mm/memcontrol-v1.c > @@ -593,29 +593,19 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry, > static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css, > struct cftype *cft) > { > - return mem_cgroup_from_css(css)->move_charge_at_immigrate; > + return 0; > } > > #ifdef CONFIG_MMU > static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css, > struct cftype *cft, u64 val) > { > - struct mem_cgroup *memcg = mem_cgroup_from_css(css); > - > pr_warn_once("Cgroup memory moving (move_charge_at_immigrate) is deprecated. " > "Please report your usecase to linux-mm@kvack.org if you " > "depend on this functionality.\n"); > > - if (val & ~MOVE_MASK) > + if (val != 0) > return -EINVAL; > - > - /* > - * No kind of locking is needed in here, because ->can_attach() will > - * check this value once in the beginning of the process, and then carry > - * on with stale data. This means that changes to this value will only > - * affect task migrations starting after the change. > - */ > - memcg->move_charge_at_immigrate = val; > return 0; > } > #else > -- > 2.43.5
On Thu, Oct 24, 2024 at 06:22:58PM -0700, Shakeel Butt wrote: > Proceed with the complete deprecation of memcg v1's charge moving > feature. The deprecation warning has been in the kernel for almost two > years and has been ported to all stable kernel since. Now is the time to > fully deprecate this feature. > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst index 270501db9f4e..286d16fc22eb 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -90,9 +90,7 @@ Brief summary of control files. used. memory.swappiness set/show swappiness parameter of vmscan (See sysctl's vm.swappiness) - memory.move_charge_at_immigrate set/show controls of moving charges - This knob is deprecated and shouldn't be - used. + memory.move_charge_at_immigrate This knob is deprecated. memory.oom_control set/show oom controls. This knob is deprecated and shouldn't be used. @@ -243,10 +241,6 @@ behind this approach is that a cgroup that aggressively uses a shared page will eventually get charged for it (once it is uncharged from the cgroup that brought it in -- this will happen on memory pressure). -But see :ref:`section 8.2 <cgroup-v1-memory-movable-charges>` when moving a -task to another cgroup, its pages may be recharged to the new cgroup, if -move_charge_at_immigrate has been chosen. - 2.4 Swap Extension -------------------------------------- @@ -756,78 +750,8 @@ If we want to change this to 1G, we can at any time use:: THIS IS DEPRECATED! -It's expensive and unreliable! It's better practice to launch workload -tasks directly from inside their target cgroup. Use dedicated workload -cgroups to allow fine-grained policy adjustments without having to -move physical pages between control domains. - -Users can move charges associated with a task along with task migration, that -is, uncharge task's pages from the old cgroup and charge them to the new cgroup. -This feature is not supported in !CONFIG_MMU environments because of lack of -page tables. - -8.1 Interface -------------- - -This feature is disabled by default. It can be enabled (and disabled again) by -writing to memory.move_charge_at_immigrate of the destination cgroup. - -If you want to enable it:: - - # echo (some positive value) > memory.move_charge_at_immigrate - -.. note:: - Each bits of move_charge_at_immigrate has its own meaning about what type - of charges should be moved. See :ref:`section 8.2 - <cgroup-v1-memory-movable-charges>` for details. - -.. note:: - Charges are moved only when you move mm->owner, in other words, - a leader of a thread group. - -.. note:: - If we cannot find enough space for the task in the destination cgroup, we - try to make space by reclaiming memory. Task migration may fail if we - cannot make enough space. - -.. note:: - It can take several seconds if you move charges much. - -And if you want disable it again:: - - # echo 0 > memory.move_charge_at_immigrate - -.. _cgroup-v1-memory-movable-charges: - -8.2 Type of charges which can be moved --------------------------------------- - -Each bit in move_charge_at_immigrate has its own meaning about what type of -charges should be moved. But in any case, it must be noted that an account of -a page or a swap can be moved only when it is charged to the task's current -(old) memory cgroup. - -+---+--------------------------------------------------------------------------+ -|bit| what type of charges would be moved ? | -+===+==========================================================================+ -| 0 | A charge of an anonymous page (or swap of it) used by the target task. | -| | You must enable Swap Extension (see 2.4) to enable move of swap charges. | -+---+--------------------------------------------------------------------------+ -| 1 | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory) | -| | and swaps of tmpfs file) mmapped by the target task. Unlike the case of | -| | anonymous pages, file pages (and swaps) in the range mmapped by the task | -| | will be moved even if the task hasn't done page fault, i.e. they might | -| | not be the task's "RSS", but other task's "RSS" that maps the same file. | -| | The mapcount of the page is ignored (the page can be moved independent | -| | of the mapcount). You must enable Swap Extension (see 2.4) to | -| | enable move of swap charges. | -+---+--------------------------------------------------------------------------+ - -8.3 TODO --------- - -- All of moving charge operations are done under cgroup_mutex. It's not good - behavior to hold the mutex too long, so we may need some trick. +Reading memory.move_charge_at_immigrate will always return 0 and writing +to it will always return -EINVAL. 9. Memory thresholds ==================== diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index 81d8819f13cd..9b3b1a446c65 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -593,29 +593,19 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry, static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css, struct cftype *cft) { - return mem_cgroup_from_css(css)->move_charge_at_immigrate; + return 0; } #ifdef CONFIG_MMU static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css, struct cftype *cft, u64 val) { - struct mem_cgroup *memcg = mem_cgroup_from_css(css); - pr_warn_once("Cgroup memory moving (move_charge_at_immigrate) is deprecated. " "Please report your usecase to linux-mm@kvack.org if you " "depend on this functionality.\n"); - if (val & ~MOVE_MASK) + if (val != 0) return -EINVAL; - - /* - * No kind of locking is needed in here, because ->can_attach() will - * check this value once in the beginning of the process, and then carry - * on with stale data. This means that changes to this value will only - * affect task migrations starting after the change. - */ - memcg->move_charge_at_immigrate = val; return 0; } #else