| Message ID | 20220830055949.12640-3-ryncsn@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: memcontrol: cleanup and optimize for accounting params | expand |
On Tue 30-08-22 13:59:49, Kairui Song wrote: > From: Kairui Song <kasong@tencent.com> > > cgroup_memory_noswap is used in many hot path, so make it a static key > to lower the kernel overhead. > > Using 8G of ZRAM as SWAP, benchmark using `perf stat -d -d -d --repeat 100` > with the following code snip in a non-root cgroup: > > #include <stdio.h> > #include <string.h> > #include <linux/mman.h> > #include <sys/mman.h> > #define MB 1024UL * 1024UL > int main(int argc, char **argv){ > void *p = mmap(NULL, 8000 * MB, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > memset(p, 0xff, 8000 * MB); > madvise(p, 8000 * MB, MADV_PAGEOUT); > memset(p, 0xff, 8000 * MB); > return 0; > } > > Before: > 7,021.43 msec task-clock # 0.967 CPUs utilized ( +- 0.03% ) > 4,010 context-switches # 573.853 /sec ( +- 0.01% ) > 0 cpu-migrations # 0.000 /sec > 2,052,057 page-faults # 293.661 K/sec ( +- 0.00% ) > 12,616,546,027 cycles # 1.805 GHz ( +- 0.06% ) (39.92%) > 156,823,666 stalled-cycles-frontend # 1.25% frontend cycles idle ( +- 0.10% ) (40.25%) > 310,130,812 stalled-cycles-backend # 2.47% backend cycles idle ( +- 4.39% ) (40.73%) > 18,692,516,591 instructions # 1.49 insn per cycle > # 0.01 stalled cycles per insn ( +- 0.04% ) (40.75%) > 4,907,447,976 branches # 702.283 M/sec ( +- 0.05% ) (40.30%) > 13,002,578 branch-misses # 0.26% of all branches ( +- 0.08% ) (40.48%) > 7,069,786,296 L1-dcache-loads # 1.012 G/sec ( +- 0.03% ) (40.32%) > 649,385,847 L1-dcache-load-misses # 9.13% of all L1-dcache accesses ( +- 0.07% ) (40.10%) > 1,485,448,688 L1-icache-loads # 212.576 M/sec ( +- 0.15% ) (39.49%) > 31,628,457 L1-icache-load-misses # 2.13% of all L1-icache accesses ( +- 0.40% ) (39.57%) > 6,667,311 dTLB-loads # 954.129 K/sec ( +- 0.21% ) (39.50%) > 5,668,555 dTLB-load-misses # 86.40% of all dTLB cache accesses ( +- 0.12% ) (39.03%) > 765 iTLB-loads # 109.476 /sec ( +- 21.81% ) (39.44%) > 4,370,351 iTLB-load-misses # 214320.09% of all iTLB cache accesses ( +- 1.44% ) (39.86%) > 149,207,254 L1-dcache-prefetches # 21.352 M/sec ( +- 0.13% ) (40.27%) > > 7.25869 +- 0.00203 seconds time elapsed ( +- 0.03% ) > > After: > 6,576.16 msec task-clock # 0.953 CPUs utilized ( +- 0.10% ) > 4,020 context-switches # 605.595 /sec ( +- 0.01% ) > 0 cpu-migrations # 0.000 /sec > 2,052,056 page-faults # 309.133 K/sec ( +- 0.00% ) > 11,967,619,180 cycles # 1.803 GHz ( +- 0.36% ) (38.76%) > 161,259,240 stalled-cycles-frontend # 1.38% frontend cycles idle ( +- 0.27% ) (36.58%) > 253,605,302 stalled-cycles-backend # 2.16% backend cycles idle ( +- 4.45% ) (34.78%) > 19,328,171,892 instructions # 1.65 insn per cycle > # 0.01 stalled cycles per insn ( +- 0.10% ) (31.46%) > 5,213,967,902 branches # 785.461 M/sec ( +- 0.18% ) (30.68%) > 12,385,170 branch-misses # 0.24% of all branches ( +- 0.26% ) (34.13%) > 7,271,687,822 L1-dcache-loads # 1.095 G/sec ( +- 0.12% ) (35.29%) > 649,873,045 L1-dcache-load-misses # 8.93% of all L1-dcache accesses ( +- 0.11% ) (41.41%) > 1,950,037,608 L1-icache-loads # 293.764 M/sec ( +- 0.33% ) (43.11%) > 31,365,566 L1-icache-load-misses # 1.62% of all L1-icache accesses ( +- 0.39% ) (45.89%) > 6,767,809 dTLB-loads # 1.020 M/sec ( +- 0.47% ) (48.42%) > 6,339,590 dTLB-load-misses # 95.43% of all dTLB cache accesses ( +- 0.50% ) (46.60%) > 736 iTLB-loads # 110.875 /sec ( +- 1.79% ) (48.60%) > 4,314,836 iTLB-load-misses # 518653.73% of all iTLB cache accesses ( +- 0.63% ) (42.91%) > 144,950,156 L1-dcache-prefetches # 21.836 M/sec ( +- 0.37% ) (41.39%) > > 6.89935 +- 0.00703 seconds time elapsed ( +- 0.10% ) Do you happen to have a perf profile before and after to see which of the paths really benefits from this? > The performance is clearly better. > > Signed-off-by: Kairui Song <kasong@tencent.com> Anyway, this looks good to me. I like memcg_swap_enabled() better than !cgroup_memory_noswap. The double negative was quite confusing. Acked-by: Michal Hocko <mhocko@suse.com> Thanks! > --- > mm/memcontrol.c | 27 +++++++++++++++++++-------- > 1 file changed, 19 insertions(+), 8 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 20e26ccd7dddc..8ea5589345a14 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -90,9 +90,18 @@ static bool cgroup_memory_nokmem __initdata; > > /* Whether the swap controller is active */ > #ifdef CONFIG_MEMCG_SWAP > -static bool cgroup_memory_noswap __ro_after_init; > +static bool cgroup_memory_noswap __initdata; > + > +static DEFINE_STATIC_KEY_FALSE(memcg_swap_enabled_key); > +static inline bool memcg_swap_enabled(void) > +{ > + return static_branch_likely(&memcg_swap_enabled_key); > +} > #else > -#define cgroup_memory_noswap 1 > +static inline bool memcg_swap_enabled(void) > +{ > + return false; > +} > #endif > > #ifdef CONFIG_CGROUP_WRITEBACK > @@ -102,7 +111,7 @@ static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq); > /* Whether legacy memory+swap accounting is active */ > static bool do_memsw_account(void) > { > - return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap; > + return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg_swap_enabled(); > } > > #define THRESHOLDS_EVENTS_TARGET 128 > @@ -7264,7 +7273,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry) > if (!mem_cgroup_is_root(memcg)) > page_counter_uncharge(&memcg->memory, nr_entries); > > - if (!cgroup_memory_noswap && memcg != swap_memcg) { > + if (memcg_swap_enabled() && memcg != swap_memcg) { > if (!mem_cgroup_is_root(swap_memcg)) > page_counter_charge(&swap_memcg->memsw, nr_entries); > page_counter_uncharge(&memcg->memsw, nr_entries); > @@ -7316,7 +7325,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry) > > memcg = mem_cgroup_id_get_online(memcg); > > - if (!cgroup_memory_noswap && !mem_cgroup_is_root(memcg) && > + if (memcg_swap_enabled() && !mem_cgroup_is_root(memcg) && > !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { > memcg_memory_event(memcg, MEMCG_SWAP_MAX); > memcg_memory_event(memcg, MEMCG_SWAP_FAIL); > @@ -7348,7 +7357,7 @@ void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages) > rcu_read_lock(); > memcg = mem_cgroup_from_id(id); > if (memcg) { > - if (!cgroup_memory_noswap && !mem_cgroup_is_root(memcg)) { > + if (memcg_swap_enabled() && !mem_cgroup_is_root(memcg)) { > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > page_counter_uncharge(&memcg->swap, nr_pages); > else > @@ -7364,7 +7373,7 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg) > { > long nr_swap_pages = get_nr_swap_pages(); > > - if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + if (!memcg_swap_enabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return nr_swap_pages; > for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) > nr_swap_pages = min_t(long, nr_swap_pages, > @@ -7381,7 +7390,7 @@ bool mem_cgroup_swap_full(struct page *page) > > if (vm_swap_full()) > return true; > - if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + if (!memcg_swap_enabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return false; > > memcg = page_memcg(page); > @@ -7689,6 +7698,8 @@ static int __init mem_cgroup_swap_init(void) > if (cgroup_memory_noswap) > return 0; > > + static_branch_enable(&memcg_swap_enabled_key); > + > WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files)); > WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, memsw_files)); > #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP) > -- > 2.35.2
Michal Hocko <mhocko@suse.com> 于2022年8月30日周二 15:01写道： > > On Tue 30-08-22 13:59:49, Kairui Song wrote: > > From: Kairui Song <kasong@tencent.com> > > > > cgroup_memory_noswap is used in many hot path, so make it a static key > > to lower the kernel overhead. > > > > Using 8G of ZRAM as SWAP, benchmark using `perf stat -d -d -d --repeat 100` > > with the following code snip in a non-root cgroup: > > > > #include <stdio.h> > > #include <string.h> > > #include <linux/mman.h> > > #include <sys/mman.h> > > #define MB 1024UL * 1024UL > > int main(int argc, char **argv){ > > void *p = mmap(NULL, 8000 * MB, PROT_READ | PROT_WRITE, > > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > > memset(p, 0xff, 8000 * MB); > > madvise(p, 8000 * MB, MADV_PAGEOUT); > > memset(p, 0xff, 8000 * MB); > > return 0; > > } > > > > Before: > > 7,021.43 msec task-clock # 0.967 CPUs utilized ( +- 0.03% ) > > 4,010 context-switches # 573.853 /sec ( +- 0.01% ) > > 0 cpu-migrations # 0.000 /sec > > 2,052,057 page-faults # 293.661 K/sec ( +- 0.00% ) > > 12,616,546,027 cycles # 1.805 GHz ( +- 0.06% ) (39.92%) > > 156,823,666 stalled-cycles-frontend # 1.25% frontend cycles idle ( +- 0.10% ) (40.25%) > > 310,130,812 stalled-cycles-backend # 2.47% backend cycles idle ( +- 4.39% ) (40.73%) > > 18,692,516,591 instructions # 1.49 insn per cycle > > # 0.01 stalled cycles per insn ( +- 0.04% ) (40.75%) > > 4,907,447,976 branches # 702.283 M/sec ( +- 0.05% ) (40.30%) > > 13,002,578 branch-misses # 0.26% of all branches ( +- 0.08% ) (40.48%) > > 7,069,786,296 L1-dcache-loads # 1.012 G/sec ( +- 0.03% ) (40.32%) > > 649,385,847 L1-dcache-load-misses # 9.13% of all L1-dcache accesses ( +- 0.07% ) (40.10%) > > 1,485,448,688 L1-icache-loads # 212.576 M/sec ( +- 0.15% ) (39.49%) > > 31,628,457 L1-icache-load-misses # 2.13% of all L1-icache accesses ( +- 0.40% ) (39.57%) > > 6,667,311 dTLB-loads # 954.129 K/sec ( +- 0.21% ) (39.50%) > > 5,668,555 dTLB-load-misses # 86.40% of all dTLB cache accesses ( +- 0.12% ) (39.03%) > > 765 iTLB-loads # 109.476 /sec ( +- 21.81% ) (39.44%) > > 4,370,351 iTLB-load-misses # 214320.09% of all iTLB cache accesses ( +- 1.44% ) (39.86%) > > 149,207,254 L1-dcache-prefetches # 21.352 M/sec ( +- 0.13% ) (40.27%) > > > > 7.25869 +- 0.00203 seconds time elapsed ( +- 0.03% ) > > > > After: > > 6,576.16 msec task-clock # 0.953 CPUs utilized ( +- 0.10% ) > > 4,020 context-switches # 605.595 /sec ( +- 0.01% ) > > 0 cpu-migrations # 0.000 /sec > > 2,052,056 page-faults # 309.133 K/sec ( +- 0.00% ) > > 11,967,619,180 cycles # 1.803 GHz ( +- 0.36% ) (38.76%) > > 161,259,240 stalled-cycles-frontend # 1.38% frontend cycles idle ( +- 0.27% ) (36.58%) > > 253,605,302 stalled-cycles-backend # 2.16% backend cycles idle ( +- 4.45% ) (34.78%) > > 19,328,171,892 instructions # 1.65 insn per cycle > > # 0.01 stalled cycles per insn ( +- 0.10% ) (31.46%) > > 5,213,967,902 branches # 785.461 M/sec ( +- 0.18% ) (30.68%) > > 12,385,170 branch-misses # 0.24% of all branches ( +- 0.26% ) (34.13%) > > 7,271,687,822 L1-dcache-loads # 1.095 G/sec ( +- 0.12% ) (35.29%) > > 649,873,045 L1-dcache-load-misses # 8.93% of all L1-dcache accesses ( +- 0.11% ) (41.41%) > > 1,950,037,608 L1-icache-loads # 293.764 M/sec ( +- 0.33% ) (43.11%) > > 31,365,566 L1-icache-load-misses # 1.62% of all L1-icache accesses ( +- 0.39% ) (45.89%) > > 6,767,809 dTLB-loads # 1.020 M/sec ( +- 0.47% ) (48.42%) > > 6,339,590 dTLB-load-misses # 95.43% of all dTLB cache accesses ( +- 0.50% ) (46.60%) > > 736 iTLB-loads # 110.875 /sec ( +- 1.79% ) (48.60%) > > 4,314,836 iTLB-load-misses # 518653.73% of all iTLB cache accesses ( +- 0.63% ) (42.91%) > > 144,950,156 L1-dcache-prefetches # 21.836 M/sec ( +- 0.37% ) (41.39%) > > > > 6.89935 +- 0.00703 seconds time elapsed ( +- 0.10% ) > > Do you happen to have a perf profile before and after to see which of > the paths really benefits from this? No I don't have a clear profile data about which path benefit the most. The performance benchmark result can be stably reproduced, but perf record & report & diff doesn't seems too helpful, as I can't see a significant change of any single symbols. There are quite a few callers of memcg_swap_enabled and do_memsw_account (which also calls memcg_swap_enabled), to me, it seems multiple pieces of optimization caused an overall improvement. And a lower overhead for the branch predictor may also help in general. Any other suggestion about how to collect such data?
On Tue 30-08-22 16:50:38, Kairui Song wrote: > Michal Hocko <mhocko@suse.com> 于2022年8月30日周二 15:01写道： > > > > On Tue 30-08-22 13:59:49, Kairui Song wrote: > > > From: Kairui Song <kasong@tencent.com> > > > > > > cgroup_memory_noswap is used in many hot path, so make it a static key > > > to lower the kernel overhead. > > > > > > Using 8G of ZRAM as SWAP, benchmark using `perf stat -d -d -d --repeat 100` > > > with the following code snip in a non-root cgroup: > > > > > > #include <stdio.h> > > > #include <string.h> > > > #include <linux/mman.h> > > > #include <sys/mman.h> > > > #define MB 1024UL * 1024UL > > > int main(int argc, char **argv){ > > > void *p = mmap(NULL, 8000 * MB, PROT_READ | PROT_WRITE, > > > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > > > memset(p, 0xff, 8000 * MB); > > > madvise(p, 8000 * MB, MADV_PAGEOUT); > > > memset(p, 0xff, 8000 * MB); > > > return 0; > > > } > > > > > > Before: > > > 7,021.43 msec task-clock # 0.967 CPUs utilized ( +- 0.03% ) > > > 4,010 context-switches # 573.853 /sec ( +- 0.01% ) > > > 0 cpu-migrations # 0.000 /sec > > > 2,052,057 page-faults # 293.661 K/sec ( +- 0.00% ) > > > 12,616,546,027 cycles # 1.805 GHz ( +- 0.06% ) (39.92%) > > > 156,823,666 stalled-cycles-frontend # 1.25% frontend cycles idle ( +- 0.10% ) (40.25%) > > > 310,130,812 stalled-cycles-backend # 2.47% backend cycles idle ( +- 4.39% ) (40.73%) > > > 18,692,516,591 instructions # 1.49 insn per cycle > > > # 0.01 stalled cycles per insn ( +- 0.04% ) (40.75%) > > > 4,907,447,976 branches # 702.283 M/sec ( +- 0.05% ) (40.30%) > > > 13,002,578 branch-misses # 0.26% of all branches ( +- 0.08% ) (40.48%) > > > 7,069,786,296 L1-dcache-loads # 1.012 G/sec ( +- 0.03% ) (40.32%) > > > 649,385,847 L1-dcache-load-misses # 9.13% of all L1-dcache accesses ( +- 0.07% ) (40.10%) > > > 1,485,448,688 L1-icache-loads # 212.576 M/sec ( +- 0.15% ) (39.49%) > > > 31,628,457 L1-icache-load-misses # 2.13% of all L1-icache accesses ( +- 0.40% ) (39.57%) > > > 6,667,311 dTLB-loads # 954.129 K/sec ( +- 0.21% ) (39.50%) > > > 5,668,555 dTLB-load-misses # 86.40% of all dTLB cache accesses ( +- 0.12% ) (39.03%) > > > 765 iTLB-loads # 109.476 /sec ( +- 21.81% ) (39.44%) > > > 4,370,351 iTLB-load-misses # 214320.09% of all iTLB cache accesses ( +- 1.44% ) (39.86%) > > > 149,207,254 L1-dcache-prefetches # 21.352 M/sec ( +- 0.13% ) (40.27%) > > > > > > 7.25869 +- 0.00203 seconds time elapsed ( +- 0.03% ) > > > > > > After: > > > 6,576.16 msec task-clock # 0.953 CPUs utilized ( +- 0.10% ) > > > 4,020 context-switches # 605.595 /sec ( +- 0.01% ) > > > 0 cpu-migrations # 0.000 /sec > > > 2,052,056 page-faults # 309.133 K/sec ( +- 0.00% ) > > > 11,967,619,180 cycles # 1.803 GHz ( +- 0.36% ) (38.76%) > > > 161,259,240 stalled-cycles-frontend # 1.38% frontend cycles idle ( +- 0.27% ) (36.58%) > > > 253,605,302 stalled-cycles-backend # 2.16% backend cycles idle ( +- 4.45% ) (34.78%) > > > 19,328,171,892 instructions # 1.65 insn per cycle > > > # 0.01 stalled cycles per insn ( +- 0.10% ) (31.46%) > > > 5,213,967,902 branches # 785.461 M/sec ( +- 0.18% ) (30.68%) > > > 12,385,170 branch-misses # 0.24% of all branches ( +- 0.26% ) (34.13%) > > > 7,271,687,822 L1-dcache-loads # 1.095 G/sec ( +- 0.12% ) (35.29%) > > > 649,873,045 L1-dcache-load-misses # 8.93% of all L1-dcache accesses ( +- 0.11% ) (41.41%) > > > 1,950,037,608 L1-icache-loads # 293.764 M/sec ( +- 0.33% ) (43.11%) > > > 31,365,566 L1-icache-load-misses # 1.62% of all L1-icache accesses ( +- 0.39% ) (45.89%) > > > 6,767,809 dTLB-loads # 1.020 M/sec ( +- 0.47% ) (48.42%) > > > 6,339,590 dTLB-load-misses # 95.43% of all dTLB cache accesses ( +- 0.50% ) (46.60%) > > > 736 iTLB-loads # 110.875 /sec ( +- 1.79% ) (48.60%) > > > 4,314,836 iTLB-load-misses # 518653.73% of all iTLB cache accesses ( +- 0.63% ) (42.91%) > > > 144,950,156 L1-dcache-prefetches # 21.836 M/sec ( +- 0.37% ) (41.39%) > > > > > > 6.89935 +- 0.00703 seconds time elapsed ( +- 0.10% ) > > > > Do you happen to have a perf profile before and after to see which of > > the paths really benefits from this? > > No I don't have a clear profile data about which path benefit the most. > The performance benchmark result can be stably reproduced, but perf > record & report & diff doesn't seems too helpful, as I can't see a > significant change of any single symbols. This is a good information on its own as it suggests that the overhead is spilled over multiple places rather than a single hot spot. Good to have in the changelog.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 20e26ccd7dddc..8ea5589345a14 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -90,9 +90,18 @@ static bool cgroup_memory_nokmem __initdata; /* Whether the swap controller is active */ #ifdef CONFIG_MEMCG_SWAP -static bool cgroup_memory_noswap __ro_after_init; +static bool cgroup_memory_noswap __initdata; + +static DEFINE_STATIC_KEY_FALSE(memcg_swap_enabled_key); +static inline bool memcg_swap_enabled(void) +{ + return static_branch_likely(&memcg_swap_enabled_key); +} #else -#define cgroup_memory_noswap 1 +static inline bool memcg_swap_enabled(void) +{ + return false; +} #endif #ifdef CONFIG_CGROUP_WRITEBACK @@ -102,7 +111,7 @@ static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq); /* Whether legacy memory+swap accounting is active */ static bool do_memsw_account(void) { - return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap; + return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg_swap_enabled(); } #define THRESHOLDS_EVENTS_TARGET 128 @@ -7264,7 +7273,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry) if (!mem_cgroup_is_root(memcg)) page_counter_uncharge(&memcg->memory, nr_entries); - if (!cgroup_memory_noswap && memcg != swap_memcg) { + if (memcg_swap_enabled() && memcg != swap_memcg) { if (!mem_cgroup_is_root(swap_memcg)) page_counter_charge(&swap_memcg->memsw, nr_entries); page_counter_uncharge(&memcg->memsw, nr_entries); @@ -7316,7 +7325,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry) memcg = mem_cgroup_id_get_online(memcg); - if (!cgroup_memory_noswap && !mem_cgroup_is_root(memcg) && + if (memcg_swap_enabled() && !mem_cgroup_is_root(memcg) && !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { memcg_memory_event(memcg, MEMCG_SWAP_MAX); memcg_memory_event(memcg, MEMCG_SWAP_FAIL); @@ -7348,7 +7357,7 @@ void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages) rcu_read_lock(); memcg = mem_cgroup_from_id(id); if (memcg) { - if (!cgroup_memory_noswap && !mem_cgroup_is_root(memcg)) { + if (memcg_swap_enabled() && !mem_cgroup_is_root(memcg)) { if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) page_counter_uncharge(&memcg->swap, nr_pages); else @@ -7364,7 +7373,7 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg) { long nr_swap_pages = get_nr_swap_pages(); - if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) + if (!memcg_swap_enabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) return nr_swap_pages; for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) nr_swap_pages = min_t(long, nr_swap_pages, @@ -7381,7 +7390,7 @@ bool mem_cgroup_swap_full(struct page *page) if (vm_swap_full()) return true; - if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) + if (!memcg_swap_enabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) return false; memcg = page_memcg(page); @@ -7689,6 +7698,8 @@ static int __init mem_cgroup_swap_init(void) if (cgroup_memory_noswap) return 0; + static_branch_enable(&memcg_swap_enabled_key); + WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files)); WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, memsw_files)); #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)