| Message ID | 20200422204708.2176080-3-guro@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | The new cgroup slab memory controller | expand |
On Wed, Apr 22, 2020 at 01:46:51PM -0700, Roman Gushchin wrote: > To implement per-object slab memory accounting, we need to > convert slab vmstat counters to bytes. Actually, out of > 4 levels of counters: global, per-node, per-memcg and per-lruvec > only two last levels will require byte-sized counters. > It's because global and per-node counters will be counting the > number of slab pages, and per-memcg and per-lruvec will be > counting the amount of memory taken by charged slab objects. > > Converting all vmstat counters to bytes or even all slab > counters to bytes would introduce an additional overhead. > So instead let's store global and per-node counters > in pages, and memcg and lruvec counters in bytes. > > To make the API clean all access helpers (both on the read > and write sides) are dealing with bytes. > > To avoid back-and-forth conversions a new flavor of helpers > is introduced, which always returns values in pages: > node_page_state_pages() and global_node_page_state_pages(). > > Actually new helpers are just reading raw values. Old helpers are > simple wrappers, which perform a conversion if the vmstat items are > in bytes. Because at the moment no one actually need bytes, > there are WARN_ON_ONCE() macroses inside to warn about inappropriate > use cases. > > Thanks to Johannes Weiner for the idea of having the byte-sized API > on top of the page-sized internal storage. > > Signed-off-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
On 4/22/20 10:46 PM, Roman Gushchin wrote: > To implement per-object slab memory accounting, we need to > convert slab vmstat counters to bytes. Actually, out of > 4 levels of counters: global, per-node, per-memcg and per-lruvec > only two last levels will require byte-sized counters. > It's because global and per-node counters will be counting the > number of slab pages, and per-memcg and per-lruvec will be > counting the amount of memory taken by charged slab objects. > > Converting all vmstat counters to bytes or even all slab > counters to bytes would introduce an additional overhead. > So instead let's store global and per-node counters > in pages, and memcg and lruvec counters in bytes. > > To make the API clean all access helpers (both on the read > and write sides) are dealing with bytes. > > To avoid back-and-forth conversions a new flavor of helpers > is introduced, which always returns values in pages: > node_page_state_pages() and global_node_page_state_pages(). > > Actually new helpers are just reading raw values. Old helpers are > simple wrappers, which perform a conversion if the vmstat items are > in bytes. Because at the moment no one actually need bytes, > there are WARN_ON_ONCE() macroses inside to warn about inappropriate > use cases. > > Thanks to Johannes Weiner for the idea of having the byte-sized API > on top of the page-sized internal storage. > > Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-By: Vlastimil Babka <vbabka@suse.cz> But it's somewhat complicated, so it would be great to document it in comments of e.g. include/linux/vmstat.h that what the API returns as unsigned long, can be either bytes or pages depending on vmstat_item_in_bytes(). > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -204,6 +204,11 @@ enum node_stat_item { > NR_VM_NODE_STAT_ITEMS > }; > > +static __always_inline bool vmstat_item_in_bytes(enum node_stat_item item) This should also have a comment explaining if it's talking about API or storage, as it's not immediately obvious. > +{ > + return false; > +} > + > /* > * We do arithmetic on the LRU lists in various places in the code, > * so it is important to keep the active lists LRU_ACTIVE higher in
On 5/20/20 1:31 PM, Vlastimil Babka wrote: > On 4/22/20 10:46 PM, Roman Gushchin wrote: >> To implement per-object slab memory accounting, we need to >> convert slab vmstat counters to bytes. Actually, out of >> 4 levels of counters: global, per-node, per-memcg and per-lruvec >> only two last levels will require byte-sized counters. >> It's because global and per-node counters will be counting the >> number of slab pages, and per-memcg and per-lruvec will be >> counting the amount of memory taken by charged slab objects. >> >> Converting all vmstat counters to bytes or even all slab >> counters to bytes would introduce an additional overhead. >> So instead let's store global and per-node counters >> in pages, and memcg and lruvec counters in bytes. >> >> To make the API clean all access helpers (both on the read >> and write sides) are dealing with bytes. >> >> To avoid back-and-forth conversions a new flavor of helpers >> is introduced, which always returns values in pages: >> node_page_state_pages() and global_node_page_state_pages(). >> >> Actually new helpers are just reading raw values. Old helpers are >> simple wrappers, which perform a conversion if the vmstat items are >> in bytes. Because at the moment no one actually need bytes, >> there are WARN_ON_ONCE() macroses inside to warn about inappropriate >> use cases. >> >> Thanks to Johannes Weiner for the idea of having the byte-sized API >> on top of the page-sized internal storage. >> >> Signed-off-by: Roman Gushchin <guro@fb.com> > > Reviewed-By: Vlastimil Babka <vbabka@suse.cz> > > But it's somewhat complicated, so it would be great to document it in comments > of e.g. include/linux/vmstat.h that what the API returns as unsigned long, can > be either bytes or pages depending on vmstat_item_in_bytes(). Also forgot to add that if those WARN_ON_ONCEs are going to stay, they should rather become VM_WARN_ON_ONCEs
diff --git a/drivers/base/node.c b/drivers/base/node.c index 10d7e818e118..9d6afb7d2ccd 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -507,7 +507,7 @@ static ssize_t node_read_vmstat(struct device *dev, for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) n += sprintf(buf+n, "%s %lu\n", node_stat_name(i), - node_page_state(pgdat, i)); + node_page_state_pages(pgdat, i)); return n; } diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index c1fbda9ddd1f..22fe65edf425 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -204,6 +204,11 @@ enum node_stat_item { NR_VM_NODE_STAT_ITEMS }; +static __always_inline bool vmstat_item_in_bytes(enum node_stat_item item) +{ + return false; +} + /* * We do arithmetic on the LRU lists in various places in the code, * so it is important to keep the active lists LRU_ACTIVE higher in diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index 292485f3d24d..117763827cd0 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -190,7 +190,8 @@ static inline unsigned long global_zone_page_state(enum zone_stat_item item) return x; } -static inline unsigned long global_node_page_state(enum node_stat_item item) +static inline +unsigned long global_node_page_state_pages(enum node_stat_item item) { long x = atomic_long_read(&vm_node_stat[item]); #ifdef CONFIG_SMP @@ -200,6 +201,16 @@ static inline unsigned long global_node_page_state(enum node_stat_item item) return x; } +static inline unsigned long global_node_page_state(enum node_stat_item item) +{ + unsigned long x = global_node_page_state_pages(item); + + if (WARN_ON_ONCE(vmstat_item_in_bytes(item))) + return x << PAGE_SHIFT; + + return x; +} + static inline unsigned long zone_page_state(struct zone *zone, enum zone_stat_item item) { @@ -240,9 +251,12 @@ extern unsigned long sum_zone_node_page_state(int node, extern unsigned long sum_zone_numa_state(int node, enum numa_stat_item item); extern unsigned long node_page_state(struct pglist_data *pgdat, enum node_stat_item item); +extern unsigned long node_page_state_pages(struct pglist_data *pgdat, + enum node_stat_item item); #else #define sum_zone_node_page_state(node, item) global_zone_page_state(item) #define node_page_state(node, item) global_node_page_state(item) +#define node_page_state_pages(node, item) global_node_page_state_pages(item) #endif /* CONFIG_NUMA */ #ifdef CONFIG_SMP diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f6ff20095105..5f700fa8b78c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -681,13 +681,16 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz) */ void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val) { - long x; + long x, threshold = MEMCG_CHARGE_BATCH; if (mem_cgroup_disabled()) return; + if (vmstat_item_in_bytes(idx)) + threshold <<= PAGE_SHIFT; + x = val + __this_cpu_read(memcg->vmstats_percpu->stat[idx]); - if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) { + if (unlikely(abs(x) > threshold)) { struct mem_cgroup *mi; /* @@ -719,7 +722,7 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, pg_data_t *pgdat = lruvec_pgdat(lruvec); struct mem_cgroup_per_node *pn; struct mem_cgroup *memcg; - long x; + long x, threshold = MEMCG_CHARGE_BATCH; pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); memcg = pn->memcg; @@ -730,8 +733,11 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, /* Update lruvec */ __this_cpu_add(pn->lruvec_stat_local->count[idx], val); + if (vmstat_item_in_bytes(idx)) + threshold <<= PAGE_SHIFT; + x = val + __this_cpu_read(pn->lruvec_stat_cpu->count[idx]); - if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) { + if (unlikely(abs(x) > threshold)) { struct mem_cgroup_per_node *pi; for (pi = pn; pi; pi = parent_nodeinfo(pi, pgdat->node_id)) diff --git a/mm/vmstat.c b/mm/vmstat.c index 6fd1407f4632..7ac13f6d189a 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -341,6 +341,11 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item, long x; long t; + if (vmstat_item_in_bytes(item)) { + WARN_ON(delta & (PAGE_SIZE - 1)); + delta >>= PAGE_SHIFT; + } + x = delta + __this_cpu_read(*p); t = __this_cpu_read(pcp->stat_threshold); @@ -398,6 +403,8 @@ void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item) s8 __percpu *p = pcp->vm_node_stat_diff + item; s8 v, t; + WARN_ON_ONCE(vmstat_item_in_bytes(item)); + v = __this_cpu_inc_return(*p); t = __this_cpu_read(pcp->stat_threshold); if (unlikely(v > t)) { @@ -442,6 +449,8 @@ void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item) s8 __percpu *p = pcp->vm_node_stat_diff + item; s8 v, t; + WARN_ON_ONCE(vmstat_item_in_bytes(item)); + v = __this_cpu_dec_return(*p); t = __this_cpu_read(pcp->stat_threshold); if (unlikely(v < - t)) { @@ -541,6 +550,11 @@ static inline void mod_node_state(struct pglist_data *pgdat, s8 __percpu *p = pcp->vm_node_stat_diff + item; long o, n, t, z; + if (vmstat_item_in_bytes(item)) { + WARN_ON_ONCE(delta & (PAGE_SIZE - 1)); + delta >>= PAGE_SHIFT; + } + do { z = 0; /* overflow to node counters */ @@ -989,8 +1003,8 @@ unsigned long sum_zone_numa_state(int node, /* * Determine the per node value of a stat item. */ -unsigned long node_page_state(struct pglist_data *pgdat, - enum node_stat_item item) +unsigned long node_page_state_pages(struct pglist_data *pgdat, + enum node_stat_item item) { long x = atomic_long_read(&pgdat->vm_stat[item]); #ifdef CONFIG_SMP @@ -999,6 +1013,17 @@ unsigned long node_page_state(struct pglist_data *pgdat, #endif return x; } + +unsigned long node_page_state(struct pglist_data *pgdat, + enum node_stat_item item) +{ + unsigned long x = node_page_state_pages(pgdat, item); + + if (WARN_ON_ONCE(vmstat_item_in_bytes(item))) + return x << PAGE_SHIFT; + + return x; +} #endif #ifdef CONFIG_COMPACTION @@ -1571,7 +1596,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat, seq_printf(m, "\n per-node stats"); for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) { seq_printf(m, "\n %-12s %lu", node_stat_name(i), - node_page_state(pgdat, i)); + node_page_state_pages(pgdat, i)); } } seq_printf(m, @@ -1692,7 +1717,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos) #endif for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) - v[i] = global_node_page_state(i); + v[i] = global_node_page_state_pages(i); v += NR_VM_NODE_STAT_ITEMS; global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
To implement per-object slab memory accounting, we need to convert slab vmstat counters to bytes. Actually, out of 4 levels of counters: global, per-node, per-memcg and per-lruvec only two last levels will require byte-sized counters. It's because global and per-node counters will be counting the number of slab pages, and per-memcg and per-lruvec will be counting the amount of memory taken by charged slab objects. Converting all vmstat counters to bytes or even all slab counters to bytes would introduce an additional overhead. So instead let's store global and per-node counters in pages, and memcg and lruvec counters in bytes. To make the API clean all access helpers (both on the read and write sides) are dealing with bytes. To avoid back-and-forth conversions a new flavor of helpers is introduced, which always returns values in pages: node_page_state_pages() and global_node_page_state_pages(). Actually new helpers are just reading raw values. Old helpers are simple wrappers, which perform a conversion if the vmstat items are in bytes. Because at the moment no one actually need bytes, there are WARN_ON_ONCE() macroses inside to warn about inappropriate use cases. Thanks to Johannes Weiner for the idea of having the byte-sized API on top of the page-sized internal storage. Signed-off-by: Roman Gushchin <guro@fb.com> --- drivers/base/node.c | 2 +- include/linux/mmzone.h | 5 +++++ include/linux/vmstat.h | 16 +++++++++++++++- mm/memcontrol.c | 14 ++++++++++---- mm/vmstat.c | 33 +++++++++++++++++++++++++++++---- 5 files changed, 60 insertions(+), 10 deletions(-)