Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/

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Export of internal Abseil changes -- 341670bce317dd6af8d3c066970230591a47e80c by Martijn Vels <mvels@google.com>: Change GetStack() and GetParentStack() to return absl::Span PiperOrigin-RevId: 368765721 -- 6aaab9536d6957303c7aba100c3afaa6fb0ea2c8 by Martijn Vels <mvels@google.com>: Remove locking from parent stack. This change removes the need to lock all access to `parent_stack' by making the 'copy constructor' logic specify the 'copied from' CordzInfo (where available) to the TrackCord function, after which parent_stack is immutable. PiperOrigin-RevId: 368760630 -- b19e2059cada35a8ede994833018edac94de6ddc by Martijn Vels <mvels@google.com>: Add cordz instrumentation to Cord PiperOrigin-RevId: 368746225 -- 67b8bbf980f0f4e1db79aa32968e9a715a09b51a by Martijn Vels <mvels@google.com>: Create ABSL_INTERNAL_CORDZ_ENABLED define controlling when Cordz code is enabled There are specific builds and condtions under which we don't support cordz sampling, which is per this change represented by ABSL_INTERNAL_CORDZ_ENABLED being defined. PiperOrigin-RevId: 368731603 -- 8cbfe0e3169637a620f4b66ad2bc2ce340879cb0 by Martijn Vels <mvels@google.com>: Add a `rep` property to CordzInfo to be managed by Cord logic. This change adds a `rep` property to CordzInfo, which is intended to be used by collection logic. Mini design: Cord invokes TrackCord() providing the active 'root' cordrep of the newly sampled Cord, returning a CordzInfo with a weak (uncounted) reference to this root. Cord invokes `SetCordRep()` each time the root cordrep of the sampled Cord is updated while holding `mutex()`. Cord must also obtain `mutex()` _before_ removing a reference on the old root. i.e.: Cord must guarantee that the (weak) reference held in CordzInfo is at all times valid. CordzInfo collection code can then safely obtain a (reference counted) rep pointer by adding a reference to `rep_` while holding `mutex()`. This requires only a very brief critical section inside CordzInfo logic, minimizing contention with concurrent Cord updates. Cord code should typically obtain and hold `mutex()` for the entirety of each mutating Cord operation on a sampled cord. As Cord is thread compatible, it never competes on the lock with any other thread. The only possible concurrent access is from Cordz collection code, which should be a relatively rare event. PiperOrigin-RevId: 368673758 -- 1255120dce2bdd6b4205a34a0e555e0b74b6152f by Martijn Vels <mvels@google.com>: Remove 'depth' from active recorded metrics. Going forward we do not 'live' record depth (and size), but will observe these at collection time only. PiperOrigin-RevId: 368636572 -- 83e5146e35f221736b49e9f0a8805f8c159a51db by Martijn Vels <mvels@google.com>: Make cordz targets visible in OSS PiperOrigin-RevId: 368615010 -- dcb16a4f1239151f0a8c70a8cfeb29dabbd113b8 by Martijn Vels <mvels@google.com>: Internal cleanup PiperOrigin-RevId: 368514666 GitOrigin-RevId: 341670bce317dd6af8d3c066970230591a47e80c Change-Id: I94cecfbbd441eb386f99fc5186c468a7a5538862
4 years ago
// Copyright 2019 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ABSL_STRINGS_INTERNAL_CORDZ_FUNCTIONS_H_
#define ABSL_STRINGS_INTERNAL_CORDZ_FUNCTIONS_H_
Export of internal Abseil changes -- 341670bce317dd6af8d3c066970230591a47e80c by Martijn Vels <mvels@google.com>: Change GetStack() and GetParentStack() to return absl::Span PiperOrigin-RevId: 368765721 -- 6aaab9536d6957303c7aba100c3afaa6fb0ea2c8 by Martijn Vels <mvels@google.com>: Remove locking from parent stack. This change removes the need to lock all access to `parent_stack' by making the 'copy constructor' logic specify the 'copied from' CordzInfo (where available) to the TrackCord function, after which parent_stack is immutable. PiperOrigin-RevId: 368760630 -- b19e2059cada35a8ede994833018edac94de6ddc by Martijn Vels <mvels@google.com>: Add cordz instrumentation to Cord PiperOrigin-RevId: 368746225 -- 67b8bbf980f0f4e1db79aa32968e9a715a09b51a by Martijn Vels <mvels@google.com>: Create ABSL_INTERNAL_CORDZ_ENABLED define controlling when Cordz code is enabled There are specific builds and condtions under which we don't support cordz sampling, which is per this change represented by ABSL_INTERNAL_CORDZ_ENABLED being defined. PiperOrigin-RevId: 368731603 -- 8cbfe0e3169637a620f4b66ad2bc2ce340879cb0 by Martijn Vels <mvels@google.com>: Add a `rep` property to CordzInfo to be managed by Cord logic. This change adds a `rep` property to CordzInfo, which is intended to be used by collection logic. Mini design: Cord invokes TrackCord() providing the active 'root' cordrep of the newly sampled Cord, returning a CordzInfo with a weak (uncounted) reference to this root. Cord invokes `SetCordRep()` each time the root cordrep of the sampled Cord is updated while holding `mutex()`. Cord must also obtain `mutex()` _before_ removing a reference on the old root. i.e.: Cord must guarantee that the (weak) reference held in CordzInfo is at all times valid. CordzInfo collection code can then safely obtain a (reference counted) rep pointer by adding a reference to `rep_` while holding `mutex()`. This requires only a very brief critical section inside CordzInfo logic, minimizing contention with concurrent Cord updates. Cord code should typically obtain and hold `mutex()` for the entirety of each mutating Cord operation on a sampled cord. As Cord is thread compatible, it never competes on the lock with any other thread. The only possible concurrent access is from Cordz collection code, which should be a relatively rare event. PiperOrigin-RevId: 368673758 -- 1255120dce2bdd6b4205a34a0e555e0b74b6152f by Martijn Vels <mvels@google.com>: Remove 'depth' from active recorded metrics. Going forward we do not 'live' record depth (and size), but will observe these at collection time only. PiperOrigin-RevId: 368636572 -- 83e5146e35f221736b49e9f0a8805f8c159a51db by Martijn Vels <mvels@google.com>: Make cordz targets visible in OSS PiperOrigin-RevId: 368615010 -- dcb16a4f1239151f0a8c70a8cfeb29dabbd113b8 by Martijn Vels <mvels@google.com>: Internal cleanup PiperOrigin-RevId: 368514666 GitOrigin-RevId: 341670bce317dd6af8d3c066970230591a47e80c Change-Id: I94cecfbbd441eb386f99fc5186c468a7a5538862
4 years ago
#include <stdint.h>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace cord_internal {
// Returns the current sample rate. This represents the average interval
// between samples.
int32_t get_cordz_mean_interval();
// Sets the sample rate with the average interval between samples.
void set_cordz_mean_interval(int32_t mean_interval);
// Enable cordz unless any of the following applies:
// - no thread local support
// - MSVC build
// - Android build
// - Apple build
// - DLL build
// Hashtablez is turned off completely in opensource builds.
// MSVC's static atomics are dynamically initialized in debug mode, which breaks
// sampling.
#if defined(ABSL_HAVE_THREAD_LOCAL) && !defined(_MSC_VER) && \
!defined(ABSL_BUILD_DLL) && !defined(ABSL_CONSUME_DLL) && \
!defined(__ANDROID__) && !defined(__APPLE__)
#define ABSL_INTERNAL_CORDZ_ENABLED 1
#endif
#ifdef ABSL_INTERNAL_CORDZ_ENABLED
// cordz_next_sample is the number of events until the next sample event. If
// the value is 1 or less, the code will check on the next event if cordz is
// enabled, and if so, will sample the Cord. cordz is only enabled when we can
// use thread locals.
ABSL_CONST_INIT extern thread_local int64_t cordz_next_sample;
// Determines if the next sample should be profiled. If it is, the value pointed
// at by next_sample will be set with the interval until the next sample.
bool cordz_should_profile_slow();
// Returns true if the next cord should be sampled.
inline bool cordz_should_profile() {
if (ABSL_PREDICT_TRUE(cordz_next_sample > 1)) {
cordz_next_sample--;
return false;
}
return cordz_should_profile_slow();
}
// Sets the interval until the next sample (for testing only)
void cordz_set_next_sample_for_testing(int64_t next_sample);
#else // ABSL_INTERNAL_CORDZ_ENABLED
inline bool cordz_should_profile() { return false; }
inline void cordz_set_next_sample_for_testing(int64_t) {}
#endif // ABSL_INTERNAL_CORDZ_ENABLED
} // namespace cord_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_STRINGS_INTERNAL_CORDZ_FUNCTIONS_H_