1. 18 Nov, 2016 2 commits
    • Alexey Dobriyan's avatar
      netns: make struct pernet_operations::id unsigned int · c7d03a00
      Alexey Dobriyan authored
      Make struct pernet_operations::id unsigned.
      
      There are 2 reasons to do so:
      
      1)
      This field is really an index into an zero based array and
      thus is unsigned entity. Using negative value is out-of-bound
      access by definition.
      
      2)
      On x86_64 unsigned 32-bit data which are mixed with pointers
      via array indexing or offsets added or subtracted to pointers
      are preffered to signed 32-bit data.
      
      "int" being used as an array index needs to be sign-extended
      to 64-bit before being used.
      
      	void f(long *p, int i)
      	{
      		g(p[i]);
      	}
      
        roughly translates to
      
      	movsx	rsi, esi
      	mov	rdi, [rsi+...]
      	call 	g
      
      MOVSX is 3 byte instruction which isn't necessary if the variable is
      unsigned because x86_64 is zero extending by default.
      
      Now, there is net_generic() function which, you guessed it right, uses
      "int" as an array index:
      
      	static inline void *net_generic(const struct net *net, int id)
      	{
      		...
      		ptr = ng->ptr[id - 1];
      		...
      	}
      
      And this function is used a lot, so those sign extensions add up.
      
      Patch snipes ~1730 bytes on allyesconfig kernel (without all junk
      messing with code generation):
      
      	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)
      
      Unfortunately some functions actually grow bigger.
      This is a semmingly random artefact of code generation with register
      allocator being used differently. gcc decides that some variable
      needs to live in new r8+ registers and every access now requires REX
      prefix. Or it is shifted into r12, so [r12+0] addressing mode has to be
      used which is longer than [r8]
      
      However, overall balance is in negative direction:
      
      	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)
      	function                                     old     new   delta
      	nfsd4_lock                                  3886    3959     +73
      	tipc_link_build_proto_msg                   1096    1140     +44
      	mac80211_hwsim_new_radio                    2776    2808     +32
      	tipc_mon_rcv                                1032    1058     +26
      	svcauth_gss_legacy_init                     1413    1429     +16
      	tipc_bcbase_select_primary                   379     392     +13
      	nfsd4_exchange_id                           1247    1260     +13
      	nfsd4_setclientid_confirm                    782     793     +11
      		...
      	put_client_renew_locked                      494     480     -14
      	ip_set_sockfn_get                            730     716     -14
      	geneve_sock_add                              829     813     -16
      	nfsd4_sequence_done                          721     703     -18
      	nlmclnt_lookup_host                          708     686     -22
      	nfsd4_lockt                                 1085    1063     -22
      	nfs_get_client                              1077    1050     -27
      	tcf_bpf_init                                1106    1076     -30
      	nfsd4_encode_fattr                          5997    5930     -67
      	Total: Before=154856051, After=154854321, chg -0.00%
      Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      c7d03a00
    • Eric Dumazet's avatar
      udp: enable busy polling for all sockets · e68b6e50
      Eric Dumazet authored
      UDP busy polling is restricted to connected UDP sockets.
      
      This is because sk_busy_loop() only takes care of one NAPI context.
      
      There are cases where it could be extended.
      
      1) Some hosts receive traffic on a single NIC, with one RX queue.
      
      2) Some applications use SO_REUSEPORT and associated BPF filter
         to split the incoming traffic on one UDP socket per RX
      queue/thread/cpu
      
      3) Some UDP sockets are used to send/receive traffic for one flow, but
      they do not bother with connect()
      
      This patch records the napi_id of first received skb, giving more
      reach to busy polling.
      
      Tested:
      
      lpaa23:~# echo 70 >/proc/sys/net/core/busy_read
      lpaa24:~# echo 70 >/proc/sys/net/core/busy_read
      
      lpaa23:~# for f in `seq 1 10`; do ./super_netperf 1 -H lpaa24 -t UDP_RR -l 5; done
      
      Before patch :
         27867   28870   37324   41060   41215
         36764   36838   44455   41282   43843
      After patch :
         73920   73213   70147   74845   71697
         68315   68028   75219   70082   73707
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Cc: Willem de Bruijn <willemb@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      e68b6e50
  2. 17 Nov, 2016 22 commits
  3. 16 Nov, 2016 16 commits