mdebray/tvl-depot - Forge git de la DGNum

mdebray/tvl-depot

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Export of internal Abseil changes. -- 178e7a9a76fc8fcd6df6335b59139cbe644a16b9 by Jon Cohen <cohenjon@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 220523164 -- 59ef14fe7034a3148f1e9cef1f128b8ca264b444 by Jon Cohen <cohenjon@google.com>: Don't assume how much std::vector's constructors allocate in InlinedVector's test for scoped_allocator_adaptor support. PiperOrigin-RevId: 220464683 -- 6f8351be43a44a8f10bf20612b2cc744a4a911c7 by Jon Cohen <cohenjon@google.com>: Add VS Code and some Bazel output files to absl/.gitignore PiperOrigin-RevId: 220464362 -- 43fac22f8af6b6ed55309a784a9d25d837393d0e by Abseil Team <absl-team@google.com>: absl: fix SpinLock::EncodeWaitCycles If a thread has ever observed or set kSpinLockSleeper, it must never leave 0 in kWaitTimeMask because at this point it is expected to wake subsequent threads. Current calculations in EncodeWaitCycles can result in 0 in kWaitTimeMask and lead to missed wakeups. This is mostly theoretical today, because the futex call needs to finish within 128 cycles (futex can return immediately without waiting, but 128 cycles still look too low for this). But this can well fire in future if we bump granularity and/or threshold for recording contention. Use kSpinLockSleeper instead of 0. PiperOrigin-RevId: 220463123 -- def9b7e3d45c99d68cc52a4429256116d7f421f2 by Abseil Team <absl-team@google.com>: absl: optimize SpinLock::SlowLock Currently we record contention even after the first initial spin. This leads to several performance issues: 1. If we succeed in acquiring the lock after the initial spin, overall wait time can be within tens/hundreds of nanoseconds. Recording such low wait time looks completely unnecessary and excessive. From some point of view this is not even a wait, because we did not sleep. And, for example, Mutex does not record contention in this case. In majority of cases the lock should be acquired exactly during the initial spin, yet we still go through full overhead of submitting contention. 2. Whenever a thread submits contention it also calls FUTEX_WAKE (there is no way to understand if it's necessary or not when wait value is stored in the lock). So if there are just 2 threads and a brief contention, the second thread will still call FUTEX_WAKE which is completely unnecessary overhead. Don't record contention after the initial spin wait. FWIW this also removes 2 CycleClock::Now calls and EncodeWaitCycles from the common hot path. PiperOrigin-RevId: 220379972 -- 75b0c0cb214de904ea622f81ec3f4eabdc8695b0 by Derek Mauro <dmauro@google.com>: Supress MSVC warnings in raw_hash_set's use of TrailingZeros and LeadingZeros. https://github.com/abseil/abseil-cpp/issues/208 PiperOrigin-RevId: 220372204 GitOrigin-RevId: 178e7a9a76fc8fcd6df6335b59139cbe644a16b9 Change-Id: I3a66af4e050810a3274e45d4e055b2aa19ffba1b

2018-11-07 22:52:16 +01:00

2018g-9-gf0d2759