From 0c026f49e7348bce5b3c74be896ae208ae6e26a4 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Wed, 1 Aug 2018 19:12:20 +0200 Subject: [PATCH] MINOR: threads: add more consistency between certain variables in no-thread case When threads are disabled, some variables such as tid and tid_bit are still checked everywhere, the MAX_THREADS_MASK macro is ~0UL while MAX_THREADS is 1, and the all_threads_mask variable is replaced with a macro forced to zero. The compiler cannot optimize away all this code involving checks on tid and tid_bit, and we end up in special cases where all_threads_mask has to be specifically tested for being zero or not. It is not even certain the code paths are always equivalent when testing without threads and with nbthread 1. Let's change this to make sure we always present a single thread when threads are disabled, and have the relevant values declared as constants so that the compiler can optimize all the tests away. Now we have MAX_THREADS_MASK set to 1, all_threads_mask set to 1, tid set to zero and tid_bit set to 1. Doing just this has removed 4 kB of code in the no-thread case. A few checks for all_threads_mask==0 have been removed since it never happens anymore. --- include/common/hathreads.h | 26 +++++++++++++++++++++----- src/cfgparse.c | 4 ++-- src/haproxy.c | 3 +-- src/hathreads.c | 9 +++++---- 4 files changed, 29 insertions(+), 13 deletions(-) diff --git a/include/common/hathreads.h b/include/common/hathreads.h index 068b2a1530..4cf3db9bee 100644 --- a/include/common/hathreads.h +++ b/include/common/hathreads.h @@ -24,10 +24,6 @@ #include -#define MAX_THREADS_MASK ((unsigned long)-1) -extern THREAD_LOCAL unsigned int tid; /* The thread id */ -extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */ - /* Note about all_threads_mask : * - with threads support disabled, this symbol is defined as zero (0UL). * - with threads enabled, this variable is never zero, it contains the mask @@ -37,7 +33,14 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa #ifndef USE_THREAD #define MAX_THREADS 1 -#define all_threads_mask 0UL +#define MAX_THREADS_MASK 1 + +/* Only way found to replace variables with constants that are optimized away + * at build time. + */ +enum { all_threads_mask = 1UL }; +enum { tid_bit = 1UL }; +enum { tid = 0 }; #define __decl_hathreads(decl) @@ -116,6 +119,9 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa #define ha_sigmask(how, set, oldset) sigprocmask(how, set, oldset) +static inline void ha_set_tid(unsigned int tid) +{ +} static inline void __ha_barrier_load(void) { @@ -138,6 +144,7 @@ static inline void __ha_barrier_full(void) #include #define MAX_THREADS LONGBITS +#define MAX_THREADS_MASK ((unsigned long)-1) #define __decl_hathreads(decl) decl @@ -266,10 +273,19 @@ void thread_exit_sync(void); int thread_no_sync(void); int thread_need_sync(void); +extern THREAD_LOCAL unsigned int tid; /* The thread id */ +extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */ extern volatile unsigned long all_threads_mask; #define ha_sigmask(how, set, oldset) pthread_sigmask(how, set, oldset) +/* sets the thread ID and the TID bit for the current thread */ +static inline void ha_set_tid(unsigned int data) +{ + tid = data; + tid_bit = (1UL << tid); +} + #if defined(DEBUG_THREAD) || defined(DEBUG_FULL) diff --git a/src/cfgparse.c b/src/cfgparse.c index 5abe9fa0ca..1451243adc 100644 --- a/src/cfgparse.c +++ b/src/cfgparse.c @@ -7587,11 +7587,11 @@ int check_config_validity() nbproc = my_ffsl(bind_conf->bind_proc); mask = bind_conf->bind_thread[nbproc - 1]; - if (mask && !(mask & (all_threads_mask ? all_threads_mask : 1UL))) { + if (mask && !(mask & all_threads_mask)) { unsigned long new_mask = 0; while (mask) { - new_mask |= mask & (all_threads_mask ? all_threads_mask : 1UL); + new_mask |= mask & all_threads_mask; mask >>= global.nbthread; } diff --git a/src/haproxy.c b/src/haproxy.c index 810d598389..42f1f3e64f 100644 --- a/src/haproxy.c +++ b/src/haproxy.c @@ -2459,8 +2459,7 @@ static void *run_thread_poll_loop(void *data) struct per_thread_deinit_fct *ptdf; __decl_hathreads(static HA_SPINLOCK_T start_lock); - tid = *((unsigned int *)data); - tid_bit = (1UL << tid); + ha_set_tid(*((unsigned int *)data)); tv_update_date(-1,-1); list_for_each_entry(ptif, &per_thread_init_list, list) { diff --git a/src/hathreads.c b/src/hathreads.c index bfd055aa9b..595a71717c 100644 --- a/src/hathreads.c +++ b/src/hathreads.c @@ -19,8 +19,6 @@ #include #include -THREAD_LOCAL unsigned int tid = 0; -THREAD_LOCAL unsigned long tid_bit = (1UL << 0); /* Dummy I/O handler used by the sync pipe.*/ void thread_sync_io_handler(int fd) @@ -33,6 +31,9 @@ static HA_SPINLOCK_T sync_lock; static int threads_sync_pipe[2]; static unsigned long threads_want_sync = 0; volatile unsigned long all_threads_mask = 1; // nbthread 1 assumed by default +THREAD_LOCAL unsigned int tid = 0; +THREAD_LOCAL unsigned long tid_bit = (1UL << 0); + #if defined(DEBUG_THREAD) || defined(DEBUG_FULL) struct lock_stat lock_stats[LOCK_LABELS]; @@ -127,7 +128,7 @@ void thread_enter_sync() { static volatile unsigned long barrier = 0; - if (!all_threads_mask) + if (!(all_threads_mask & (all_threads_mask - 1))) return; thread_sync_barrier(&barrier); @@ -143,7 +144,7 @@ void thread_exit_sync() { static volatile unsigned long barrier = 0; - if (!all_threads_mask) + if (!(all_threads_mask & (all_threads_mask - 1))) return; if (threads_want_sync & tid_bit) -- 2.39.5