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net/dst: use a smaller percpu_counter batch for dst entries accounting

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percpu_counter_add() uses a default batch size which is quite big
on platforms with 256 cpus. (2*256 -> 512)

This means dst_entries_get_fast() can be off by +/- 2*(nr_cpus^2)
(131072 on servers with 256 cpus)

Reduce the batch size to something more reasonable, and
add logic to ip6_dst_gc() to call dst_entries_get_slow()
before calling the _very_ expensive fib6_run_gc() function.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2020-05-07 18:58:10 -07:00 committed by Jakub Kicinski
parent 790709f249
commit cf86a086a1
3 changed files with 10 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
include/net/dst_ops.h
View file

@ -53,9 +53,11 @@ static inline int dst_entries_get_slow(struct dst_ops *dst)
return percpu_counter_sum_positive(&dst->pcpuc_entries); return percpu_counter_sum_positive(&dst->pcpuc_entries);
} }
#define DST_PERCPU_COUNTER_BATCH 32
static inline void dst_entries_add(struct dst_ops *dst, int val) static inline void dst_entries_add(struct dst_ops *dst, int val)
{ {
percpu_counter_add(&dst->pcpuc_entries, val); percpu_counter_add_batch(&dst->pcpuc_entries, val,
DST_PERCPU_COUNTER_BATCH);
} }
static inline int dst_entries_init(struct dst_ops *dst) static inline int dst_entries_init(struct dst_ops *dst)

8
net/core/dst.c
View file

@ -81,11 +81,11 @@ void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
{ {
struct dst_entry *dst; struct dst_entry *dst;
if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) { if (ops->gc &&
!(flags & DST_NOCOUNT) &&
dst_entries_get_fast(ops) > ops->gc_thresh) {
if (ops->gc(ops)) { if (ops->gc(ops)) {
printk_ratelimited(KERN_NOTICE "Route cache is full: " pr_notice_ratelimited("Route cache is full: consider increasing sysctl net.ipv6.route.max_size.\n");
"consider increasing sysctl "
"net.ipv[4|6].route.max_size.\n");
return NULL; return NULL;
} }
} }

3
net/ipv6/route.c
View file

@ -3195,6 +3195,9 @@ static int ip6_dst_gc(struct dst_ops *ops)
int entries; int entries;
entries = dst_entries_get_fast(ops); entries = dst_entries_get_fast(ops);
if (entries > rt_max_size)
entries = dst_entries_get_slow(ops);
if (time_after(rt_last_gc + rt_min_interval, jiffies) && if (time_after(rt_last_gc + rt_min_interval, jiffies) &&
entries <= rt_max_size) entries <= rt_max_size)
goto out; goto out;