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This is one of the few POSIX APIs that was missing. It lets you choose a monotonic clock for your condition variables. This might improve perf on some platforms. It might also grant more flexibility with NTP configs. I know Qt is one project that believes it needs this. To introduce this, I needed to change some the *NSYNC APIs, to support passing a clock param. There's also new benchmarks, demonstrating Cosmopolitan's supremacy over many libc implementations when it comes to mutex performance. Cygwin has an alarmingly bad pthread_mutex_t implementation. It is so bad that they would have been significantly better off if they'd used naive spinlocks.
37 lines
1.6 KiB
C
Executable file
37 lines
1.6 KiB
C
Executable file
#ifndef COSMOPOLITAN_THIRD_PARTY_NSYNC_MU_SEMAPHORE_INTERNAL_H_
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#define COSMOPOLITAN_THIRD_PARTY_NSYNC_MU_SEMAPHORE_INTERNAL_H_
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#include "third_party/nsync/mu_semaphore.h"
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#include "third_party/nsync/time.h"
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COSMOPOLITAN_C_START_
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/* XNU ulock (used by cosmo futexes) is an internal API, however:
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1. Unlike GCD it's cancelable i.e. can be EINTR'd by signals
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2. We have no choice but to use ulock for joining threads
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3. Grand Central Dispatch requires a busy loop workaround
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4. ulock makes our mutexes use 20% more system time (meh)
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5. ulock makes our mutexes use 40% less wall time (good)
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6. ulock makes our mutexes use 64% less user time (woop)
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ulock is an outstanding system call that must be used.
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gcd is not an acceptable alternative to ulock. */
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#define NSYNC_USE_GRAND_CENTRAL 0
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bool nsync_mu_semaphore_init_futex(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_futex(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_with_deadline_futex(nsync_semaphore *, int, nsync_time);
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void nsync_mu_semaphore_v_futex(nsync_semaphore *);
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bool nsync_mu_semaphore_init_sem(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_sem(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_with_deadline_sem(nsync_semaphore *, int, nsync_time);
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void nsync_mu_semaphore_v_sem(nsync_semaphore *);
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bool nsync_mu_semaphore_init_gcd(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_gcd(nsync_semaphore *);
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errno_t nsync_mu_semaphore_p_with_deadline_gcd(nsync_semaphore *, int, nsync_time);
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void nsync_mu_semaphore_v_gcd(nsync_semaphore *);
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COSMOPOLITAN_C_END_
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#endif /* COSMOPOLITAN_THIRD_PARTY_NSYNC_MU_SEMAPHORE_INTERNAL_H_ */
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