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lib: cache PID & TID in zlog code

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glibc removed its pid cache a while back, and grabbing this from TLS is
faster than repeatedly calling the kernel...

Also use `intmax_t` which is more appropriate for both PID & TID.

Signed-off-by: David Lamparter <equinox@diac24.net>
This commit is contained in:
David Lamparter 2021-04-11 03:59:25 +02:00 committed by David Lamparter
parent 8b94cb4388
commit 78598fd019
2 changed files with 37 additions and 3 deletions
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35
lib/zlog.c
View File

@ -220,8 +220,15 @@ static inline void zlog_tls_set(struct zlog_tls *val)
#endif #endif
#ifdef CAN_DO_TLS #ifdef CAN_DO_TLS
static long zlog_gettid(void) static intmax_t zlog_gettid(void)
{ {
#ifndef __OpenBSD__
/* accessing a TLS variable is much faster than a syscall */
static thread_local intmax_t cached_tid = -1;
if (cached_tid != -1)
return cached_tid;
#endif
long rv = -1; long rv = -1;
#ifdef HAVE_PTHREAD_GETTHREADID_NP #ifdef HAVE_PTHREAD_GETTHREADID_NP
rv = pthread_getthreadid_np(); rv = pthread_getthreadid_np();
@ -241,6 +248,10 @@ static long zlog_gettid(void)
rv = mach_thread_self(); rv = mach_thread_self();
mach_port_deallocate(mach_task_self(), rv); mach_port_deallocate(mach_task_self(), rv);
#endif #endif
#ifndef __OpenBSD__
cached_tid = rv;
#endif
return rv; return rv;
} }
@ -260,7 +271,7 @@ void zlog_tls_buffer_init(void)
for (i = 0; i < array_size(zlog_tls->msgp); i++) for (i = 0; i < array_size(zlog_tls->msgp); i++)
zlog_tls->msgp[i] = &zlog_tls->msgs[i]; zlog_tls->msgp[i] = &zlog_tls->msgs[i];
snprintfrr(mmpath, sizeof(mmpath), "logbuf.%ld", zlog_gettid()); snprintfrr(mmpath, sizeof(mmpath), "logbuf.%jd", zlog_gettid());
mmfd = openat(zlog_tmpdirfd, mmpath, mmfd = openat(zlog_tmpdirfd, mmpath,
O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0600); O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0600);
@ -327,7 +338,7 @@ void zlog_tls_buffer_fini(void)
zlog_tls_free(zlog_tls); zlog_tls_free(zlog_tls);
zlog_tls_set(NULL); zlog_tls_set(NULL);
snprintfrr(mmpath, sizeof(mmpath), "logbuf.%ld", zlog_gettid()); snprintfrr(mmpath, sizeof(mmpath), "logbuf.%jd", zlog_gettid());
if (do_unlink && unlinkat(zlog_tmpdirfd, mmpath, 0)) if (do_unlink && unlinkat(zlog_tmpdirfd, mmpath, 0))
zlog_err("unlink logbuf: %s (%d)", strerror(errno), errno); zlog_err("unlink logbuf: %s (%d)", strerror(errno), errno);
} }
@ -342,6 +353,24 @@ void zlog_tls_buffer_fini(void)
} }
#endif #endif
void zlog_msg_pid(struct zlog_msg *msg, intmax_t *pid, intmax_t *tid)
{
#ifndef __OpenBSD__
static thread_local intmax_t cached_pid = -1;
if (cached_pid != -1)
*pid = cached_pid;
else
cached_pid = *pid = (intmax_t)getpid();
#else
*pid = (intmax_t)getpid();
#endif
#ifdef CAN_DO_TLS
*tid = zlog_gettid();
#else
*tid = *pid;
#endif
}
static inline void zlog_tls_free(void *arg) static inline void zlog_tls_free(void *arg)
{ {
struct zlog_tls *zlog_tls = arg; struct zlog_tls *zlog_tls = arg;

5
lib/zlog.h
View File

@ -178,6 +178,11 @@ extern size_t zlog_msg_ts(struct zlog_msg *msg, struct fbuf *out,
extern size_t zlog_msg_ts_3164(struct zlog_msg *msg, struct fbuf *out, extern size_t zlog_msg_ts_3164(struct zlog_msg *msg, struct fbuf *out,
uint32_t flags); uint32_t flags);
/* currently just returns the current PID/TID since we never write another
* thread's messages
*/
extern void zlog_msg_pid(struct zlog_msg *msg, intmax_t *pid, intmax_t *tid);
/* This list & struct implements the actual logging targets. It is accessed /* This list & struct implements the actual logging targets. It is accessed
* lock-free from all threads, and thus MUST only be changed atomically, i.e. * lock-free from all threads, and thus MUST only be changed atomically, i.e.
* RCU. * RCU.