From c7d03a00b56fc23c3a01a8353789ad257363e281 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Thu, 17 Nov 2016 04:58:21 +0300 Subject: netns: make struct pernet_operations::id unsigned int 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: Alexey Dobriyan Signed-off-by: David S. Miller --- fs/lockd/netns.h | 2 +- fs/lockd/svc.c | 2 +- fs/nfs/inode.c | 2 +- fs/nfs/netns.h | 2 +- fs/nfs_common/grace.c | 2 +- fs/nfsd/netns.h | 2 +- fs/nfsd/nfsctl.c | 2 +- 7 files changed, 7 insertions(+), 7 deletions(-) (limited to 'fs') diff --git a/fs/lockd/netns.h b/fs/lockd/netns.h index 5426189406c1..fb8cac88251a 100644 --- a/fs/lockd/netns.h +++ b/fs/lockd/netns.h @@ -15,6 +15,6 @@ struct lockd_net { struct list_head nsm_handles; }; -extern int lockd_net_id; +extern unsigned int lockd_net_id; #endif diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c index fc4084ef4736..1c13dd80744f 100644 --- a/fs/lockd/svc.c +++ b/fs/lockd/svc.c @@ -57,7 +57,7 @@ static struct task_struct *nlmsvc_task; static struct svc_rqst *nlmsvc_rqst; unsigned long nlmsvc_timeout; -int lockd_net_id; +unsigned int lockd_net_id; /* * These can be set at insmod time (useful for NFS as root filesystem), diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index bf4ec5ecc97e..ce42dd00e4ee 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -2015,7 +2015,7 @@ static void nfsiod_stop(void) destroy_workqueue(wq); } -int nfs_net_id; +unsigned int nfs_net_id; EXPORT_SYMBOL_GPL(nfs_net_id); static int nfs_net_init(struct net *net) diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h index fbce0d885d4c..5fbd2bde91ba 100644 --- a/fs/nfs/netns.h +++ b/fs/nfs/netns.h @@ -35,6 +35,6 @@ struct nfs_net { #endif }; -extern int nfs_net_id; +extern unsigned int nfs_net_id; #endif diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c index fd8c9a5bcac4..420d3a0ab258 100644 --- a/fs/nfs_common/grace.c +++ b/fs/nfs_common/grace.c @@ -9,7 +9,7 @@ #include #include -static int grace_net_id; +static unsigned int grace_net_id; static DEFINE_SPINLOCK(grace_lock); /** diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index ee36efd5aece..3714231a9d0f 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -124,5 +124,5 @@ struct nfsd_net { /* Simple check to find out if a given net was properly initialized */ #define nfsd_netns_ready(nn) ((nn)->sessionid_hashtbl) -extern int nfsd_net_id; +extern unsigned int nfsd_net_id; #endif /* __NFSD_NETNS_H__ */ diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index 36b2af931e06..2857e46d5cc5 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1201,7 +1201,7 @@ static int create_proc_exports_entry(void) } #endif -int nfsd_net_id; +unsigned int nfsd_net_id; static __net_init int nfsd_init_net(struct net *net) { -- cgit v1.2.3