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authorEric Dumazet <edumazet@google.com>2021-10-14 16:41:26 +0300
committerDavid S. Miller <davem@davemloft.net>2021-10-15 13:28:34 +0300
commit19757cebf0c5016a1f36f7fe9810a9f0b33c0832 (patch)
tree9d2349b63f328c9cb79fe6580215f823f8765b78 /drivers/net/ethernet/chelsio
parent0b93aed2842d950e8d2625e975e5a57febeff33d (diff)
downloadlinux-19757cebf0c5016a1f36f7fe9810a9f0b33c0832.tar.xz
tcp: switch orphan_count to bare per-cpu counters
Use of percpu_counter structure to track count of orphaned sockets is causing problems on modern hosts with 256 cpus or more. Stefan Bach reported a serious spinlock contention in real workloads, that I was able to reproduce with a netfilter rule dropping incoming FIN packets. 53.56% server [kernel.kallsyms] [k] queued_spin_lock_slowpath | ---queued_spin_lock_slowpath | --53.51%--_raw_spin_lock_irqsave | --53.51%--__percpu_counter_sum tcp_check_oom | |--39.03%--__tcp_close | tcp_close | inet_release | inet6_release | sock_close | __fput | ____fput | task_work_run | exit_to_usermode_loop | do_syscall_64 | entry_SYSCALL_64_after_hwframe | __GI___libc_close | --14.48%--tcp_out_of_resources tcp_write_timeout tcp_retransmit_timer tcp_write_timer_handler tcp_write_timer call_timer_fn expire_timers __run_timers run_timer_softirq __softirqentry_text_start As explained in commit cf86a086a180 ("net/dst: use a smaller percpu_counter batch for dst entries accounting"), default batch size is too big for the default value of tcp_max_orphans (262144). But even if we reduce batch sizes, there would still be cases where the estimated count of orphans is beyond the limit, and where tcp_too_many_orphans() has to call the expensive percpu_counter_sum_positive(). One solution is to use plain per-cpu counters, and have a timer to periodically refresh this cache. Updating this cache every 100ms seems about right, tcp pressure state is not radically changing over shorter periods. percpu_counter was nice 15 years ago while hosts had less than 16 cpus, not anymore by current standards. v2: Fix the build issue for CONFIG_CRYPTO_DEV_CHELSIO_TLS=m, reported by kernel test robot <lkp@intel.com> Remove unused socket argument from tcp_too_many_orphans() Fixes: dd24c00191d5 ("net: Use a percpu_counter for orphan_count") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Stefan Bach <sfb@google.com> Cc: Neal Cardwell <ncardwell@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/chelsio')
-rw-r--r--drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c2
-rw-r--r--drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h2
2 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
index bcad69c48074..4af5561cbfc5 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
@@ -870,7 +870,7 @@ static void do_abort_syn_rcv(struct sock *child, struct sock *parent)
* created only after 3 way handshake is done.
*/
sock_orphan(child);
- percpu_counter_inc((child)->sk_prot->orphan_count);
+ INC_ORPHAN_COUNT(child);
chtls_release_resources(child);
chtls_conn_done(child);
} else {
diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
index b1161bdeda4d..f61ca657601c 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
@@ -95,7 +95,7 @@ struct deferred_skb_cb {
#define WSCALE_OK(tp) ((tp)->rx_opt.wscale_ok)
#define TSTAMP_OK(tp) ((tp)->rx_opt.tstamp_ok)
#define SACK_OK(tp) ((tp)->rx_opt.sack_ok)
-#define INC_ORPHAN_COUNT(sk) percpu_counter_inc((sk)->sk_prot->orphan_count)
+#define INC_ORPHAN_COUNT(sk) this_cpu_inc(*(sk)->sk_prot->orphan_count)
/* TLS SKB */
#define skb_ulp_tls_inline(skb) (ULP_SKB_CB(skb)->ulp.tls.ofld)