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authorGravatar Abseil Team <absl-team@google.com>2020-10-26 09:50:44 -0700
committerGravatar vslashg <gfalcon@google.com>2020-10-26 16:18:57 -0400
commit5bf048b8425cc0a342e4647932de19e25ffd6ad7 (patch)
tree230a48e04f01169f632ee13b4f6c7e218b5cc177 /absl/base
parent1e3d25b2657228bd691ee938cfd37d487f48054b (diff)
Export of internal Abseil changes
-- 730bb88bee556aa11fa19aa33e1434cb6fa78985 by Evan Brown <ezb@google.com>: Support missing allocator-related constructors in b-tree. See [reference](https://en.cppreference.com/w/cpp/container/set/set). Also use allocator_traits::select_on_container_copy_construction() to get allocator for copy construction. PiperOrigin-RevId: 339058322 -- b6cc121689ae3e452d1db2d66122cb198d25142b by Derek Mauro <dmauro@google.com>: Fix more sign-compare warnings PiperOrigin-RevId: 339057920 -- 0e2c62da1dcaf6529abab952bdcc96c6de2d9506 by Abseil Team <absl-team@google.com>: Add missing <limits> include PiperOrigin-RevId: 339054753 -- d5a9ec2d1e40fe6359e720942e4955009ee415ec by Derek Mauro <dmauro@google.com>: Stop disabling sign-compare warnings for non-test targets. Our users complain about these. This does not catch issues in header-only libraries (like btree.h) but we may work on those in the future PiperOrigin-RevId: 338967089 -- 0c062c542a4c61ea0f65d25811827c0858e3adde by Abseil Team <absl-team@google.com>: Improve cache-locality for ThreadIdentity and PerThreadSynch. This is a change based on an observation in RPC benchmarks that shows significant cycles being spent in waking up a thread, 99.8% of which was on cache misses. Investigating this a bit more, it turns out to be due to sharing the cache line with the waiter state. To fix this issue, the following changes are introduced: - Reorder fields in PerThreadSync so that it fits in a single cache line The size of this structure was 80 bytes before this change. Note: Manually inspected all booleans to make sure they are not modified by multiple threads concurrently. PiperOrigin-RevId: 338852058 -- a90d6f2b2346385017e32dd8ae1b5ca691a5863f by Derek Mauro <dmauro@google.com>: Delete GCC 4.9 test script. It is no longer supported PiperOrigin-RevId: 338779452 -- 7274008d4757e88869110be9db39d03d911ae2b5 by Abseil Team <absl-team@google.com>: Fix the usage example in which SetFlag should take a pointer. PiperOrigin-RevId: 338744529 GitOrigin-RevId: 730bb88bee556aa11fa19aa33e1434cb6fa78985 Change-Id: Iff99594c4022e60e482a392d334b376c7ae8883e
Diffstat (limited to 'absl/base')
-rw-r--r--absl/base/internal/thread_identity.h79
1 files changed, 39 insertions, 40 deletions
diff --git a/absl/base/internal/thread_identity.h b/absl/base/internal/thread_identity.h
index ceb109b4..c61d1feb 100644
--- a/absl/base/internal/thread_identity.h
+++ b/absl/base/internal/thread_identity.h
@@ -32,6 +32,7 @@
#include "absl/base/config.h"
#include "absl/base/internal/per_thread_tls.h"
+#include "absl/base/optimization.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
@@ -69,30 +70,28 @@ struct PerThreadSynch {
// is using this PerThreadSynch as a terminator. Its
// skip field must not be filled in because the loop
// might then skip over the terminator.
-
- // The wait parameters of the current wait. waitp is null if the
- // thread is not waiting. Transitions from null to non-null must
- // occur before the enqueue commit point (state = kQueued in
- // Enqueue() and CondVarEnqueue()). Transitions from non-null to
- // null must occur after the wait is finished (state = kAvailable in
- // Mutex::Block() and CondVar::WaitCommon()). This field may be
- // changed only by the thread that describes this PerThreadSynch. A
- // special case is Fer(), which calls Enqueue() on another thread,
- // but with an identical SynchWaitParams pointer, thus leaving the
- // pointer unchanged.
- SynchWaitParams *waitp;
-
- bool suppress_fatal_errors; // If true, try to proceed even in the face of
- // broken invariants. This is used within fatal
- // signal handlers to improve the chances of
- // debug logging information being output
- // successfully.
-
- intptr_t readers; // Number of readers in mutex.
- int priority; // Priority of thread (updated every so often).
-
- // When priority will next be read (cycles).
- int64_t next_priority_read_cycles;
+ bool wake; // This thread is to be woken from a Mutex.
+ // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the
+ // waiter is waiting on the mutex as part of a CV Wait or Mutex Await.
+ //
+ // The value of "x->cond_waiter" is meaningless if "x" is not on a
+ // Mutex waiter list.
+ bool cond_waiter;
+ bool maybe_unlocking; // Valid at head of Mutex waiter queue;
+ // true if UnlockSlow could be searching
+ // for a waiter to wake. Used for an optimization
+ // in Enqueue(). true is always a valid value.
+ // Can be reset to false when the unlocker or any
+ // writer releases the lock, or a reader fully
+ // releases the lock. It may not be set to false
+ // by a reader that decrements the count to
+ // non-zero. protected by mutex spinlock
+ bool suppress_fatal_errors; // If true, try to proceed even in the face
+ // of broken invariants. This is used within
+ // fatal signal handlers to improve the
+ // chances of debug logging information being
+ // output successfully.
+ int priority; // Priority of thread (updated every so often).
// State values:
// kAvailable: This PerThreadSynch is available.
@@ -111,30 +110,30 @@ struct PerThreadSynch {
};
std::atomic<State> state;
- bool maybe_unlocking; // Valid at head of Mutex waiter queue;
- // true if UnlockSlow could be searching
- // for a waiter to wake. Used for an optimization
- // in Enqueue(). true is always a valid value.
- // Can be reset to false when the unlocker or any
- // writer releases the lock, or a reader fully releases
- // the lock. It may not be set to false by a reader
- // that decrements the count to non-zero.
- // protected by mutex spinlock
+ // The wait parameters of the current wait. waitp is null if the
+ // thread is not waiting. Transitions from null to non-null must
+ // occur before the enqueue commit point (state = kQueued in
+ // Enqueue() and CondVarEnqueue()). Transitions from non-null to
+ // null must occur after the wait is finished (state = kAvailable in
+ // Mutex::Block() and CondVar::WaitCommon()). This field may be
+ // changed only by the thread that describes this PerThreadSynch. A
+ // special case is Fer(), which calls Enqueue() on another thread,
+ // but with an identical SynchWaitParams pointer, thus leaving the
+ // pointer unchanged.
+ SynchWaitParams* waitp;
- bool wake; // This thread is to be woken from a Mutex.
+ intptr_t readers; // Number of readers in mutex.
- // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the
- // waiter is waiting on the mutex as part of a CV Wait or Mutex Await.
- //
- // The value of "x->cond_waiter" is meaningless if "x" is not on a
- // Mutex waiter list.
- bool cond_waiter;
+ // When priority will next be read (cycles).
+ int64_t next_priority_read_cycles;
// Locks held; used during deadlock detection.
// Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity().
SynchLocksHeld *all_locks;
};
+// The instances of this class are allocated in NewThreadIdentity() with an
+// alignment of PerThreadSynch::kAlignment.
struct ThreadIdentity {
// Must be the first member. The Mutex implementation requires that
// the PerThreadSynch object associated with each thread is