Re: Question about ip_defrag
flat view
From: Florian Westphal <fw@strlen.de>
Date: 2017-08-28 14:03:43
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
Possibly related (same subject, not in this thread)
- 2017-08-24 · Re: Question about ip_defrag · Jesper Dangaard Brouer <hidden>
liujian (CE) [off-list ref] wrote:
Hi I checked our 3.10 kernel, we had backported all percpu_counter bug fix in lib/percpu_counter.c and include/linux/percpu_counter.h. And I check 4.13-rc6, also has the issue if NIC's rx cpu num big enough.quoted
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the issue: Ip_defrag fail caused by frag_mem_limit reached 4M(frags.high_thresh). At this moment,sum_frag_mem_limit is about 10K.So should we change ipfrag high/low thresh to a reasonable value ? And if it is, is there a standard to change the value?
Each cpu can have frag_percpu_counter_batch bytes rest doesn't know about so with 64 cpus that is ~8 mbyte. possible solutions: 1. reduce frag_percpu_counter_batch to 16k or so 2. make both low and high thresh depend on NR_CPUS liujian, does this change help in any way?
diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c@@ -123,6 +123,17 @@ static bool inet_fragq_should_evict(const struct inet_frag_queue *q) frag_mem_limit(q->net) >= q->net->low_thresh; } +/* ->mem batch size is huge, this can cause severe discrepancies + * between actual value (sum of pcpu values) and the global estimate. + * + * Use a smaller batch to give an opportunity for the global estimate + * to more accurately reflect current state. + */ +static void update_frag_mem_limit(struct netns_frags *nf, unsigned int batch) +{ + percpu_counter_add_batch(&nf->mem, 0, batch); +} + static unsigned int inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) {
@@ -146,8 +157,12 @@ inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) spin_unlock(&hb->chain_lock); - hlist_for_each_entry_safe(fq, n, &expired, list_evictor) + hlist_for_each_entry_safe(fq, n, &expired, list_evictor) { + struct netns_frags *nf = fq->net; + f->frag_expire((unsigned long) fq); + update_frag_mem_limit(nf, 1); + } return evicted; }
@@ -396,8 +411,10 @@ struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, struct inet_frag_queue *q; int depth = 0; - if (frag_mem_limit(nf) > nf->low_thresh) + if (frag_mem_limit(nf) > nf->low_thresh) { inet_frag_schedule_worker(f); + update_frag_mem_limit(nf, SKB_TRUESIZE(1500) * 16); + } hash &= (INETFRAGS_HASHSZ - 1); hb = &f->hash[hash];
@@ -416,6 +433,8 @@ struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, if (depth <= INETFRAGS_MAXDEPTH) return inet_frag_create(nf, f, key); + update_frag_mem_limit(nf, 1); + if (inet_frag_may_rebuild(f)) { if (!f->rebuild) f->rebuild = true;