1. 03 Feb, 2018 2 commits
  2. 18 Nov, 2016 1 commit
    • 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
  3. 13 Aug, 2015 1 commit
  4. 17 Sep, 2014 1 commit
  5. 27 Jul, 2012 2 commits
  6. 03 Oct, 2008 1 commit
    • J. Bruce Fields's avatar
      nfsd: common grace period control · af558e33
      J. Bruce Fields authored
      Rewrite grace period code to unify management of grace period across
      lockd and nfsd.  The current code has lockd and nfsd cooperate to
      compute a grace period which is satisfactory to them both, and then
      individually enforce it.  This creates a slight race condition, since
      the enforcement is not coordinated.  It's also more complicated than
      necessary.
      
      Here instead we have lockd and nfsd each inform common code when they
      enter the grace period, and when they're ready to leave the grace
      period, and allow normal locking only after both of them are ready to
      leave.
      
      We also expect the locks_start_grace()/locks_end_grace() interface here
      to be simpler to build on for future cluster/high-availability work,
      which may require (for example) putting individual filesystems into
      grace, or enforcing grace periods across multiple cluster nodes.
      Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
      af558e33