* [PATCH net 1/2] Revert "net: use lib/percpu_counter API for fragmentation mem accounting"
2017-09-01 9:26 [PATCH net 0/2] net: revert lib/percpu_counter API for fragmentation mem accounting Jesper Dangaard Brouer
@ 2017-09-01 9:26 ` Jesper Dangaard Brouer
2017-09-01 9:30 ` Florian Westphal
2017-09-01 9:26 ` [PATCH net 2/2] Revert "net: fix percpu memory leaks" Jesper Dangaard Brouer
2017-09-03 18:01 ` [PATCH net 0/2] net: revert lib/percpu_counter API for fragmentation mem accounting David Miller
2 siblings, 1 reply; 5+ messages in thread
From: Jesper Dangaard Brouer @ 2017-09-01 9:26 UTC (permalink / raw)
To: netdev; +Cc: mkubecek, Florian Westphal, liujian56, Jesper Dangaard Brouer
This reverts commit 6d7b857d541ecd1d9bd997c97242d4ef94b19de2.
There is a bug in fragmentation codes use of the percpu_counter API,
that can cause issues on systems with many CPUs.
The frag_mem_limit() just reads the global counter (fbc->count),
without considering other CPUs can have upto batch size (130K) that
haven't been subtracted yet. Due to the 3MBytes lower thresh limit,
this become dangerous at >=24 CPUs (3*1024*1024/130000=24).
The correct API usage would be to use __percpu_counter_compare() which
does the right thing, and takes into account the number of (online)
CPUs and batch size, to account for this and call __percpu_counter_sum()
when needed.
We choose to revert the use of the lib/percpu_counter API for frag
memory accounting for several reasons:
1) On systems with CPUs > 24, the heavier fully locked
__percpu_counter_sum() is always invoked, which will be more
expensive than the atomic_t that is reverted to.
Given systems with more than 24 CPUs are becoming common this doesn't
seem like a good option. To mitigate this, the batch size could be
decreased and thresh be increased.
2) The add_frag_mem_limit+sub_frag_mem_limit pairs happen on the RX
CPU, before SKBs are pushed into sockets on remote CPUs. Given
NICs can only hash on L2 part of the IP-header, the NIC-RXq's will
likely be limited. Thus, a fair chance that atomic add+dec happen
on the same CPU.
Revert note that commit 1d6119baf061 ("net: fix percpu memory leaks")
removed init_frag_mem_limit() and instead use inet_frags_init_net().
After this revert, inet_frags_uninit_net() becomes empty.
Fixes: 6d7b857d541e ("net: use lib/percpu_counter API for fragmentation mem accounting")
Fixes: 1d6119baf061 ("net: fix percpu memory leaks")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/inet_frag.h | 30 +++++++++---------------------
net/ipv4/inet_fragment.c | 4 +---
2 files changed, 10 insertions(+), 24 deletions(-)
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 6fdcd2427776..fa635aa6d0b9 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -1,14 +1,9 @@
#ifndef __NET_FRAG_H__
#define __NET_FRAG_H__
-#include <linux/percpu_counter.h>
-
struct netns_frags {
- /* The percpu_counter "mem" need to be cacheline aligned.
- * mem.count must not share cacheline with other writers
- */
- struct percpu_counter mem ____cacheline_aligned_in_smp;
-
+ /* Keep atomic mem on separate cachelines in structs that include it */
+ atomic_t mem ____cacheline_aligned_in_smp;
/* sysctls */
int timeout;
int high_thresh;
@@ -110,11 +105,11 @@ void inet_frags_fini(struct inet_frags *);
static inline int inet_frags_init_net(struct netns_frags *nf)
{
- return percpu_counter_init(&nf->mem, 0, GFP_KERNEL);
+ atomic_set(&nf->mem, 0);
+ return 0;
}
static inline void inet_frags_uninit_net(struct netns_frags *nf)
{
- percpu_counter_destroy(&nf->mem);
}
void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f);
@@ -140,31 +135,24 @@ static inline bool inet_frag_evicting(struct inet_frag_queue *q)
/* Memory Tracking Functions. */
-/* The default percpu_counter batch size is not big enough to scale to
- * fragmentation mem acct sizes.
- * The mem size of a 64K fragment is approx:
- * (44 fragments * 2944 truesize) + frag_queue struct(200) = 129736 bytes
- */
-static unsigned int frag_percpu_counter_batch = 130000;
-
static inline int frag_mem_limit(struct netns_frags *nf)
{
- return percpu_counter_read(&nf->mem);
+ return atomic_read(&nf->mem);
}
static inline void sub_frag_mem_limit(struct netns_frags *nf, int i)
{
- percpu_counter_add_batch(&nf->mem, -i, frag_percpu_counter_batch);
+ atomic_sub(i, &nf->mem);
}
static inline void add_frag_mem_limit(struct netns_frags *nf, int i)
{
- percpu_counter_add_batch(&nf->mem, i, frag_percpu_counter_batch);
+ atomic_add(i, &nf->mem);
}
-static inline unsigned int sum_frag_mem_limit(struct netns_frags *nf)
+static inline int sum_frag_mem_limit(struct netns_frags *nf)
{
- return percpu_counter_sum_positive(&nf->mem);
+ return atomic_read(&nf->mem);
}
/* RFC 3168 support :
diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index 96e95e83cc61..af74d0433453 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -234,10 +234,8 @@ void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
cond_resched();
if (read_seqretry(&f->rnd_seqlock, seq) ||
- percpu_counter_sum(&nf->mem))
+ sum_frag_mem_limit(nf))
goto evict_again;
-
- percpu_counter_destroy(&nf->mem);
}
EXPORT_SYMBOL(inet_frags_exit_net);
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH net 2/2] Revert "net: fix percpu memory leaks"
2017-09-01 9:26 [PATCH net 0/2] net: revert lib/percpu_counter API for fragmentation mem accounting Jesper Dangaard Brouer
2017-09-01 9:26 ` [PATCH net 1/2] Revert "net: use lib/percpu_counter API for fragmentation mem accounting" Jesper Dangaard Brouer
@ 2017-09-01 9:26 ` Jesper Dangaard Brouer
2017-09-03 18:01 ` [PATCH net 0/2] net: revert lib/percpu_counter API for fragmentation mem accounting David Miller
2 siblings, 0 replies; 5+ messages in thread
From: Jesper Dangaard Brouer @ 2017-09-01 9:26 UTC (permalink / raw)
To: netdev; +Cc: mkubecek, Florian Westphal, liujian56, Jesper Dangaard Brouer
This reverts commit 1d6119baf0610f813eb9d9580eb4fd16de5b4ceb.
After reverting commit 6d7b857d541e ("net: use lib/percpu_counter API
for fragmentation mem accounting") then here is no need for this
fix-up patch. As percpu_counter is no longer used, it cannot
memory leak it any-longer.
Fixes: 6d7b857d541e ("net: use lib/percpu_counter API for fragmentation mem accounting")
Fixes: 1d6119baf061 ("net: fix percpu memory leaks")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/inet_frag.h | 7 +------
net/ieee802154/6lowpan/reassembly.c | 11 +++--------
net/ipv4/ip_fragment.c | 12 +++---------
net/ipv6/netfilter/nf_conntrack_reasm.c | 12 +++---------
net/ipv6/reassembly.c | 12 +++---------
5 files changed, 13 insertions(+), 41 deletions(-)
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index fa635aa6d0b9..fc59e0775e00 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -103,15 +103,10 @@ struct inet_frags {
int inet_frags_init(struct inet_frags *);
void inet_frags_fini(struct inet_frags *);
-static inline int inet_frags_init_net(struct netns_frags *nf)
+static inline void inet_frags_init_net(struct netns_frags *nf)
{
atomic_set(&nf->mem, 0);
- return 0;
}
-static inline void inet_frags_uninit_net(struct netns_frags *nf)
-{
-}
-
void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f);
void inet_frag_kill(struct inet_frag_queue *q, struct inet_frags *f);
diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
index 30d875dff6b5..f85b08baff16 100644
--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -580,19 +580,14 @@ static int __net_init lowpan_frags_init_net(struct net *net)
{
struct netns_ieee802154_lowpan *ieee802154_lowpan =
net_ieee802154_lowpan(net);
- int res;
ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
- res = inet_frags_init_net(&ieee802154_lowpan->frags);
- if (res)
- return res;
- res = lowpan_frags_ns_sysctl_register(net);
- if (res)
- inet_frags_uninit_net(&ieee802154_lowpan->frags);
- return res;
+ inet_frags_init_net(&ieee802154_lowpan->frags);
+
+ return lowpan_frags_ns_sysctl_register(net);
}
static void __net_exit lowpan_frags_exit_net(struct net *net)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 9a8cfac503dc..46408c220d9d 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -844,8 +844,6 @@ static void __init ip4_frags_ctl_register(void)
static int __net_init ipv4_frags_init_net(struct net *net)
{
- int res;
-
/* Fragment cache limits.
*
* The fragment memory accounting code, (tries to) account for
@@ -871,13 +869,9 @@ static int __net_init ipv4_frags_init_net(struct net *net)
net->ipv4.frags.max_dist = 64;
- res = inet_frags_init_net(&net->ipv4.frags);
- if (res)
- return res;
- res = ip4_frags_ns_ctl_register(net);
- if (res)
- inet_frags_uninit_net(&net->ipv4.frags);
- return res;
+ inet_frags_init_net(&net->ipv4.frags);
+
+ return ip4_frags_ns_ctl_register(net);
}
static void __net_exit ipv4_frags_exit_net(struct net *net)
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index 986d4ca38832..b263bf3a19f7 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -622,18 +622,12 @@ EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
static int nf_ct_net_init(struct net *net)
{
- int res;
-
net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
- res = inet_frags_init_net(&net->nf_frag.frags);
- if (res)
- return res;
- res = nf_ct_frag6_sysctl_register(net);
- if (res)
- inet_frags_uninit_net(&net->nf_frag.frags);
- return res;
+ inet_frags_init_net(&net->nf_frag.frags);
+
+ return nf_ct_frag6_sysctl_register(net);
}
static void nf_ct_net_exit(struct net *net)
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index e1da5b888cc4..846012eae526 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -714,19 +714,13 @@ static void ip6_frags_sysctl_unregister(void)
static int __net_init ipv6_frags_init_net(struct net *net)
{
- int res;
-
net->ipv6.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
net->ipv6.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
net->ipv6.frags.timeout = IPV6_FRAG_TIMEOUT;
- res = inet_frags_init_net(&net->ipv6.frags);
- if (res)
- return res;
- res = ip6_frags_ns_sysctl_register(net);
- if (res)
- inet_frags_uninit_net(&net->ipv6.frags);
- return res;
+ inet_frags_init_net(&net->ipv6.frags);
+
+ return ip6_frags_ns_sysctl_register(net);
}
static void __net_exit ipv6_frags_exit_net(struct net *net)
^ permalink raw reply related [flat|nested] 5+ messages in thread