Revision 4df910620bebb5cfe234af16ac8f6474b60215fd authored by Feng Tang on 25 November 2020, 05:22:21 UTC, committed by Linus Torvalds on 26 November 2020, 17:35:49 UTC
0day reported one -22.7% regression for will-it-scale page_fault2 case [1] on a 4 sockets 144 CPU platform, and bisected to it to be caused by Waiman's optimization (commit bd0b230fe1) of saving one 'struct page_counter' space for 'struct mem_cgroup'. Initially we thought it was due to the cache alignment change introduced by the patch, but further debug shows that it is due to some hot data members ('vmstats_local', 'vmstats_percpu', 'vmstats') sit in 2 adjacent cacheline (2N and 2N+1 cacheline), and when adjacent cache line prefetch is enabled, it triggers an "extended level" of cache false sharing for 2 adjacent cache lines. So exchange the 2 member blocks, while keeping mostly the original cache alignment, which can restore and even enhance the performance, and save 64 bytes of space for 'struct mem_cgroup' (from 2880 to 2816, with 0day's default RHEL-8.3 kernel config) [1]. https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ Fixes: bd0b230fe145 ("mm/memcg: unify swap and memsw page counters") Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: Feng Tang <feng.tang@intel.com> Acked-by: Waiman Long <longman@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent fa02fcd
udplite.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* UDPLITE An implementation of the UDP-Lite protocol (RFC 3828).
*
* Authors: Gerrit Renker <gerrit@erg.abdn.ac.uk>
*
* Changes:
* Fixes:
*/
#define pr_fmt(fmt) "UDPLite: " fmt
#include <linux/export.h>
#include <linux/proc_fs.h>
#include "udp_impl.h"
struct udp_table udplite_table __read_mostly;
EXPORT_SYMBOL(udplite_table);
static int udplite_rcv(struct sk_buff *skb)
{
return __udp4_lib_rcv(skb, &udplite_table, IPPROTO_UDPLITE);
}
static int udplite_err(struct sk_buff *skb, u32 info)
{
return __udp4_lib_err(skb, info, &udplite_table);
}
static const struct net_protocol udplite_protocol = {
.handler = udplite_rcv,
.err_handler = udplite_err,
.no_policy = 1,
.netns_ok = 1,
};
struct proto udplite_prot = {
.name = "UDP-Lite",
.owner = THIS_MODULE,
.close = udp_lib_close,
.connect = ip4_datagram_connect,
.disconnect = udp_disconnect,
.ioctl = udp_ioctl,
.init = udplite_sk_init,
.destroy = udp_destroy_sock,
.setsockopt = udp_setsockopt,
.getsockopt = udp_getsockopt,
.sendmsg = udp_sendmsg,
.recvmsg = udp_recvmsg,
.sendpage = udp_sendpage,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
.rehash = udp_v4_rehash,
.get_port = udp_v4_get_port,
.memory_allocated = &udp_memory_allocated,
.sysctl_mem = sysctl_udp_mem,
.obj_size = sizeof(struct udp_sock),
.h.udp_table = &udplite_table,
};
EXPORT_SYMBOL(udplite_prot);
static struct inet_protosw udplite4_protosw = {
.type = SOCK_DGRAM,
.protocol = IPPROTO_UDPLITE,
.prot = &udplite_prot,
.ops = &inet_dgram_ops,
.flags = INET_PROTOSW_PERMANENT,
};
#ifdef CONFIG_PROC_FS
static struct udp_seq_afinfo udplite4_seq_afinfo = {
.family = AF_INET,
.udp_table = &udplite_table,
};
static int __net_init udplite4_proc_init_net(struct net *net)
{
if (!proc_create_net_data("udplite", 0444, net->proc_net, &udp_seq_ops,
sizeof(struct udp_iter_state), &udplite4_seq_afinfo))
return -ENOMEM;
return 0;
}
static void __net_exit udplite4_proc_exit_net(struct net *net)
{
remove_proc_entry("udplite", net->proc_net);
}
static struct pernet_operations udplite4_net_ops = {
.init = udplite4_proc_init_net,
.exit = udplite4_proc_exit_net,
};
static __init int udplite4_proc_init(void)
{
return register_pernet_subsys(&udplite4_net_ops);
}
#else
static inline int udplite4_proc_init(void)
{
return 0;
}
#endif
void __init udplite4_register(void)
{
udp_table_init(&udplite_table, "UDP-Lite");
if (proto_register(&udplite_prot, 1))
goto out_register_err;
if (inet_add_protocol(&udplite_protocol, IPPROTO_UDPLITE) < 0)
goto out_unregister_proto;
inet_register_protosw(&udplite4_protosw);
if (udplite4_proc_init())
pr_err("%s: Cannot register /proc!\n", __func__);
return;
out_unregister_proto:
proto_unregister(&udplite_prot);
out_register_err:
pr_crit("%s: Cannot add UDP-Lite protocol\n", __func__);
}
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