| Message ID | 20230829081142.3619-6-urezki@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Mitigate a vmap lock contention v2 | expand |
On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > Similar to busy VA, lazily-freed area is stored to a node > it belongs to. Such approach does not require any global > locking primitive, instead an access becomes scalable what > mitigates a contention. > > This patch removes a global purge-lock, global purge-tree > and global purge list. > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > --- > mm/vmalloc.c | 135 +++++++++++++++++++++++++++++++-------------------- > 1 file changed, 82 insertions(+), 53 deletions(-) LGTM, Reviewed-by: Baoquan He <bhe@redhat.com> > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index ae0368c314ff..5a8a9c1370b6 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -733,10 +733,6 @@ static DEFINE_SPINLOCK(free_vmap_area_lock); > LIST_HEAD(vmap_area_list); > static bool vmap_initialized __read_mostly; > > -static struct rb_root purge_vmap_area_root = RB_ROOT; > -static LIST_HEAD(purge_vmap_area_list); > -static DEFINE_SPINLOCK(purge_vmap_area_lock); > - > /* > * This kmem_cache is used for vmap_area objects. Instead of > * allocating from slab we reuse an object from this cache to > @@ -784,6 +780,12 @@ struct rb_list { > struct vmap_node { > /* Bookkeeping data of this node. */ > struct rb_list busy; > + struct rb_list lazy; > + > + /* > + * Ready-to-free areas. > + */ > + struct list_head purge_list; > }; > > static struct vmap_node *nodes, snode; > @@ -1768,40 +1770,22 @@ static DEFINE_MUTEX(vmap_purge_lock); > > /* for per-CPU blocks */ > static void purge_fragmented_blocks_allcpus(void); > +static cpumask_t purge_nodes; > > /* > * Purges all lazily-freed vmap areas. > */ > -static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > +static unsigned long > +purge_vmap_node(struct vmap_node *vn) > { > - unsigned long resched_threshold; > - unsigned int num_purged_areas = 0; > - struct list_head local_purge_list; > + unsigned long num_purged_areas = 0; > struct vmap_area *va, *n_va; > > - lockdep_assert_held(&vmap_purge_lock); > - > - spin_lock(&purge_vmap_area_lock); > - purge_vmap_area_root = RB_ROOT; > - list_replace_init(&purge_vmap_area_list, &local_purge_list); > - spin_unlock(&purge_vmap_area_lock); > - > - if (unlikely(list_empty(&local_purge_list))) > - goto out; > - > - start = min(start, > - list_first_entry(&local_purge_list, > - struct vmap_area, list)->va_start); > - > - end = max(end, > - list_last_entry(&local_purge_list, > - struct vmap_area, list)->va_end); > - > - flush_tlb_kernel_range(start, end); > - resched_threshold = lazy_max_pages() << 1; > + if (list_empty(&vn->purge_list)) > + return 0; > > spin_lock(&free_vmap_area_lock); > - list_for_each_entry_safe(va, n_va, &local_purge_list, list) { > + list_for_each_entry_safe(va, n_va, &vn->purge_list, list) { > unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT; > unsigned long orig_start = va->va_start; > unsigned long orig_end = va->va_end; > @@ -1823,13 +1807,55 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > > atomic_long_sub(nr, &vmap_lazy_nr); > num_purged_areas++; > - > - if (atomic_long_read(&vmap_lazy_nr) < resched_threshold) > - cond_resched_lock(&free_vmap_area_lock); > } > spin_unlock(&free_vmap_area_lock); > > -out: > + return num_purged_areas; > +} > + > +/* > + * Purges all lazily-freed vmap areas. > + */ > +static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > +{ > + unsigned long num_purged_areas = 0; > + struct vmap_node *vn; > + int i; > + > + lockdep_assert_held(&vmap_purge_lock); > + purge_nodes = CPU_MASK_NONE; > + > + for (i = 0; i < nr_nodes; i++) { > + vn = &nodes[i]; > + > + INIT_LIST_HEAD(&vn->purge_list); > + > + if (RB_EMPTY_ROOT(&vn->lazy.root)) > + continue; > + > + spin_lock(&vn->lazy.lock); > + WRITE_ONCE(vn->lazy.root.rb_node, NULL); > + list_replace_init(&vn->lazy.head, &vn->purge_list); > + spin_unlock(&vn->lazy.lock); > + > + start = min(start, list_first_entry(&vn->purge_list, > + struct vmap_area, list)->va_start); > + > + end = max(end, list_last_entry(&vn->purge_list, > + struct vmap_area, list)->va_end); > + > + cpumask_set_cpu(i, &purge_nodes); > + } > + > + if (cpumask_weight(&purge_nodes) > 0) { > + flush_tlb_kernel_range(start, end); > + > + for_each_cpu(i, &purge_nodes) { > + vn = &nodes[i]; > + num_purged_areas += purge_vmap_node(vn); > + } > + } > + > trace_purge_vmap_area_lazy(start, end, num_purged_areas); > return num_purged_areas > 0; > } > @@ -1848,16 +1874,9 @@ static void reclaim_and_purge_vmap_areas(void) > > static void drain_vmap_area_work(struct work_struct *work) > { > - unsigned long nr_lazy; > - > - do { > - mutex_lock(&vmap_purge_lock); > - __purge_vmap_area_lazy(ULONG_MAX, 0); > - mutex_unlock(&vmap_purge_lock); > - > - /* Recheck if further work is required. */ > - nr_lazy = atomic_long_read(&vmap_lazy_nr); > - } while (nr_lazy > lazy_max_pages()); > + mutex_lock(&vmap_purge_lock); > + __purge_vmap_area_lazy(ULONG_MAX, 0); > + mutex_unlock(&vmap_purge_lock); > } > > /* > @@ -1867,6 +1886,7 @@ static void drain_vmap_area_work(struct work_struct *work) > */ > static void free_vmap_area_noflush(struct vmap_area *va) > { > + struct vmap_node *vn = addr_to_node(va->va_start); > unsigned long nr_lazy_max = lazy_max_pages(); > unsigned long va_start = va->va_start; > unsigned long nr_lazy; > @@ -1880,10 +1900,9 @@ static void free_vmap_area_noflush(struct vmap_area *va) > /* > * Merge or place it to the purge tree/list. > */ > - spin_lock(&purge_vmap_area_lock); > - merge_or_add_vmap_area(va, > - &purge_vmap_area_root, &purge_vmap_area_list); > - spin_unlock(&purge_vmap_area_lock); > + spin_lock(&vn->lazy.lock); > + merge_or_add_vmap_area(va, &vn->lazy.root, &vn->lazy.head); > + spin_unlock(&vn->lazy.lock); > > trace_free_vmap_area_noflush(va_start, nr_lazy, nr_lazy_max); > > @@ -4390,15 +4409,21 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v) > > static void show_purge_info(struct seq_file *m) > { > + struct vmap_node *vn; > struct vmap_area *va; > + int i; > > - spin_lock(&purge_vmap_area_lock); > - list_for_each_entry(va, &purge_vmap_area_list, list) { > - seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n", > - (void *)va->va_start, (void *)va->va_end, > - va->va_end - va->va_start); > + for (i = 0; i < nr_nodes; i++) { > + vn = &nodes[i]; > + > + spin_lock(&vn->lazy.lock); > + list_for_each_entry(va, &vn->lazy.head, list) { > + seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n", > + (void *)va->va_start, (void *)va->va_end, > + va->va_end - va->va_start); > + } > + spin_unlock(&vn->lazy.lock); > } > - spin_unlock(&purge_vmap_area_lock); > } > > static int s_show(struct seq_file *m, void *p) > @@ -4545,6 +4570,10 @@ static void vmap_init_nodes(void) > vn->busy.root = RB_ROOT; > INIT_LIST_HEAD(&vn->busy.head); > spin_lock_init(&vn->busy.lock); > + > + vn->lazy.root = RB_ROOT; > + INIT_LIST_HEAD(&vn->lazy.head); > + spin_lock_init(&vn->lazy.lock); > } > } > > -- > 2.30.2 >
> On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > > Similar to busy VA, lazily-freed area is stored to a node > > it belongs to. Such approach does not require any global > > locking primitive, instead an access becomes scalable what > > mitigates a contention. > > > > This patch removes a global purge-lock, global purge-tree > > and global purge list. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > --- > > mm/vmalloc.c | 135 +++++++++++++++++++++++++++++++-------------------- > > 1 file changed, 82 insertions(+), 53 deletions(-) > > LGTM, > > Reviewed-by: Baoquan He <bhe@redhat.com> > Applied. Thank you for review! -- Uladzislau Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index ae0368c314ff..5a8a9c1370b6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -733,10 +733,6 @@ static DEFINE_SPINLOCK(free_vmap_area_lock); LIST_HEAD(vmap_area_list); static bool vmap_initialized __read_mostly; -static struct rb_root purge_vmap_area_root = RB_ROOT; -static LIST_HEAD(purge_vmap_area_list); -static DEFINE_SPINLOCK(purge_vmap_area_lock); - /* * This kmem_cache is used for vmap_area objects. Instead of * allocating from slab we reuse an object from this cache to @@ -784,6 +780,12 @@ struct rb_list { struct vmap_node { /* Bookkeeping data of this node. */ struct rb_list busy; + struct rb_list lazy; + + /* + * Ready-to-free areas. + */ + struct list_head purge_list; }; static struct vmap_node *nodes, snode; @@ -1768,40 +1770,22 @@ static DEFINE_MUTEX(vmap_purge_lock); /* for per-CPU blocks */ static void purge_fragmented_blocks_allcpus(void); +static cpumask_t purge_nodes; /* * Purges all lazily-freed vmap areas. */ -static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) +static unsigned long +purge_vmap_node(struct vmap_node *vn) { - unsigned long resched_threshold; - unsigned int num_purged_areas = 0; - struct list_head local_purge_list; + unsigned long num_purged_areas = 0; struct vmap_area *va, *n_va; - lockdep_assert_held(&vmap_purge_lock); - - spin_lock(&purge_vmap_area_lock); - purge_vmap_area_root = RB_ROOT; - list_replace_init(&purge_vmap_area_list, &local_purge_list); - spin_unlock(&purge_vmap_area_lock); - - if (unlikely(list_empty(&local_purge_list))) - goto out; - - start = min(start, - list_first_entry(&local_purge_list, - struct vmap_area, list)->va_start); - - end = max(end, - list_last_entry(&local_purge_list, - struct vmap_area, list)->va_end); - - flush_tlb_kernel_range(start, end); - resched_threshold = lazy_max_pages() << 1; + if (list_empty(&vn->purge_list)) + return 0; spin_lock(&free_vmap_area_lock); - list_for_each_entry_safe(va, n_va, &local_purge_list, list) { + list_for_each_entry_safe(va, n_va, &vn->purge_list, list) { unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT; unsigned long orig_start = va->va_start; unsigned long orig_end = va->va_end; @@ -1823,13 +1807,55 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) atomic_long_sub(nr, &vmap_lazy_nr); num_purged_areas++; - - if (atomic_long_read(&vmap_lazy_nr) < resched_threshold) - cond_resched_lock(&free_vmap_area_lock); } spin_unlock(&free_vmap_area_lock); -out: + return num_purged_areas; +} + +/* + * Purges all lazily-freed vmap areas. + */ +static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) +{ + unsigned long num_purged_areas = 0; + struct vmap_node *vn; + int i; + + lockdep_assert_held(&vmap_purge_lock); + purge_nodes = CPU_MASK_NONE; + + for (i = 0; i < nr_nodes; i++) { + vn = &nodes[i]; + + INIT_LIST_HEAD(&vn->purge_list); + + if (RB_EMPTY_ROOT(&vn->lazy.root)) + continue; + + spin_lock(&vn->lazy.lock); + WRITE_ONCE(vn->lazy.root.rb_node, NULL); + list_replace_init(&vn->lazy.head, &vn->purge_list); + spin_unlock(&vn->lazy.lock); + + start = min(start, list_first_entry(&vn->purge_list, + struct vmap_area, list)->va_start); + + end = max(end, list_last_entry(&vn->purge_list, + struct vmap_area, list)->va_end); + + cpumask_set_cpu(i, &purge_nodes); + } + + if (cpumask_weight(&purge_nodes) > 0) { + flush_tlb_kernel_range(start, end); + + for_each_cpu(i, &purge_nodes) { + vn = &nodes[i]; + num_purged_areas += purge_vmap_node(vn); + } + } + trace_purge_vmap_area_lazy(start, end, num_purged_areas); return num_purged_areas > 0; } @@ -1848,16 +1874,9 @@ static void reclaim_and_purge_vmap_areas(void) static void drain_vmap_area_work(struct work_struct *work) { - unsigned long nr_lazy; - - do { - mutex_lock(&vmap_purge_lock); - __purge_vmap_area_lazy(ULONG_MAX, 0); - mutex_unlock(&vmap_purge_lock); - - /* Recheck if further work is required. */ - nr_lazy = atomic_long_read(&vmap_lazy_nr); - } while (nr_lazy > lazy_max_pages()); + mutex_lock(&vmap_purge_lock); + __purge_vmap_area_lazy(ULONG_MAX, 0); + mutex_unlock(&vmap_purge_lock); } /* @@ -1867,6 +1886,7 @@ static void drain_vmap_area_work(struct work_struct *work) */ static void free_vmap_area_noflush(struct vmap_area *va) { + struct vmap_node *vn = addr_to_node(va->va_start); unsigned long nr_lazy_max = lazy_max_pages(); unsigned long va_start = va->va_start; unsigned long nr_lazy; @@ -1880,10 +1900,9 @@ static void free_vmap_area_noflush(struct vmap_area *va) /* * Merge or place it to the purge tree/list. */ - spin_lock(&purge_vmap_area_lock); - merge_or_add_vmap_area(va, - &purge_vmap_area_root, &purge_vmap_area_list); - spin_unlock(&purge_vmap_area_lock); + spin_lock(&vn->lazy.lock); + merge_or_add_vmap_area(va, &vn->lazy.root, &vn->lazy.head); + spin_unlock(&vn->lazy.lock); trace_free_vmap_area_noflush(va_start, nr_lazy, nr_lazy_max); @@ -4390,15 +4409,21 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v) static void show_purge_info(struct seq_file *m) { + struct vmap_node *vn; struct vmap_area *va; + int i; - spin_lock(&purge_vmap_area_lock); - list_for_each_entry(va, &purge_vmap_area_list, list) { - seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n", - (void *)va->va_start, (void *)va->va_end, - va->va_end - va->va_start); + for (i = 0; i < nr_nodes; i++) { + vn = &nodes[i]; + + spin_lock(&vn->lazy.lock); + list_for_each_entry(va, &vn->lazy.head, list) { + seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n", + (void *)va->va_start, (void *)va->va_end, + va->va_end - va->va_start); + } + spin_unlock(&vn->lazy.lock); } - spin_unlock(&purge_vmap_area_lock); } static int s_show(struct seq_file *m, void *p) @@ -4545,6 +4570,10 @@ static void vmap_init_nodes(void) vn->busy.root = RB_ROOT; INIT_LIST_HEAD(&vn->busy.head); spin_lock_init(&vn->busy.lock); + + vn->lazy.root = RB_ROOT; + INIT_LIST_HEAD(&vn->lazy.head); + spin_lock_init(&vn->lazy.lock); } }
Similar to busy VA, lazily-freed area is stored to a node it belongs to. Such approach does not require any global locking primitive, instead an access becomes scalable what mitigates a contention. This patch removes a global purge-lock, global purge-tree and global purge list. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> --- mm/vmalloc.c | 135 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 82 insertions(+), 53 deletions(-)