From: Florian Westphal <fw@strlen•de>
To: "liujian (CE)" <liujian56@huawei•com>
Cc: Jesper Dangaard Brouer <brouer@redhat•com>,
"davem@davemloft•net" <davem@davemloft•net>,
"kuznet@ms2•inr.ac.ru" <kuznet@ms2•inr.ac.ru>,
"yoshfuji@linux-ipv6•org" <yoshfuji@linux-ipv6•org>,
"elena.reshetova@intel•com" <elena.reshetova@intel•com>,
"edumazet@google•com" <edumazet@google•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"Wangkefeng (Kevin)" <wangkefeng.wang@huawei•com>,
"weiyongjun (A)" <weiyongjun1@huawei•com>
Subject: Re: Question about ip_defrag
Date: Mon, 28 Aug 2017 16:00:32 +0200 [thread overview]
Message-ID: <20170828140032.GB12926@breakpoint.cc> (raw)
In-Reply-To: <4F88C5DDA1E80143B232E89585ACE27D018F3157@DGGEMA502-MBX.china.huawei.com>
liujian (CE) <liujian56@huawei•com> 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.
>
> > > > > 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;
next prev parent reply other threads:[~2017-08-28 14:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4F88C5DDA1E80143B232E89585ACE27D018F07E2@DGGEMA502-MBX.china.huawei.com>
2017-08-24 13:53 ` Question about ip_defrag Jesper Dangaard Brouer
[not found] ` <4F88C5DDA1E80143B232E89585ACE27D018F0AE1@DGGEMA502-MBX.china.huawei.com>
2017-08-24 18:59 ` Jesper Dangaard Brouer
2017-08-25 1:33 ` liujian (CE)
2017-08-28 8:08 ` liujian (CE)
2017-08-28 14:00 ` Florian Westphal [this message]
2017-08-29 7:20 ` Jesper Dangaard Brouer
2017-08-29 7:44 ` liujian (CE)
2017-08-29 7:53 ` Florian Westphal
2017-08-30 10:58 ` Jesper Dangaard Brouer
2017-08-30 11:58 ` Florian Westphal
2017-08-30 12:22 ` Jesper Dangaard Brouer
2017-08-29 7:40 ` liujian (CE)
2017-08-29 13:01 ` liujian (CE)
2017-08-29 13:46 ` Florian Westphal
2017-08-30 1:52 ` liujian (CE)
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