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i#6938 sched migrate: Add lock contention stats (#6968)
Adds lock contention counters for mutex_dbg_owned::lock() in non-NDEBUG builds. While it's not there for release builds, the results in non-release should still be indicative of general lock behavior. When I just changed the mutex_dbg_owned header, the relese build static drmemtrace tests (e.g., the burst_* ones) were all failing with floating point exceptions. It turns out it's due to different compilation units having different values for NDEBUG. I tried to make them all the same: but we have some files that contain `#undef NDEBUG` and other complexities. So I split the mutex_dbg_owned implementation into a .cpp file and have the mutex wrapper extra fields always present. Prints the stats for sched_lock_ with the other scheduler stats. Sample results on schedule_stats on a threadsig trace show a lot of contention even with only 3 cores, which the forthcoming separate runqueue change will address: ``` $ clients/bin64/drmemtrace_launcher -indir ../build_x64_dbg_tests/drmemtrace.threadsig.5* -core_sharded -cores 3 -tool schedule_stats -verbose 1 [scheduler] Schedule lock acquired : 2196602 [scheduler] Schedule lock contended : 257580 ``` Issue: #6938
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| Original file line number | Diff line number | Diff line change |
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| /* ********************************************************** | ||
| * Copyright (c) 2024 Google, Inc. All rights reserved. | ||
| * **********************************************************/ | ||
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| /* | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions are met: | ||
| * | ||
| * * Redistributions of source code must retain the above copyright notice, | ||
| * this list of conditions and the following disclaimer. | ||
| * | ||
| * * Redistributions in binary form must reproduce the above copyright notice, | ||
| * this list of conditions and the following disclaimer in the documentation | ||
| * and/or other materials provided with the distribution. | ||
| * | ||
| * * Neither the name of Google, Inc. nor the names of its contributors may be | ||
| * used to endorse or promote products derived from this software without | ||
| * specific prior written permission. | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | ||
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | ||
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | ||
| * ARE DISCLAIMED. IN NO EVENT SHALL VMWARE, INC. OR CONTRIBUTORS BE LIABLE | ||
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | ||
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | ||
| * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | ||
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | ||
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | ||
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH | ||
| * DAMAGE. | ||
| */ | ||
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| #include <mutex> | ||
| #include <thread> | ||
| #include "mutex_dbg_owned.h" | ||
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| namespace dynamorio { | ||
| namespace drmemtrace { | ||
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| void | ||
| mutex_dbg_owned::lock() | ||
| { | ||
| #ifdef NDEBUG | ||
| lock_.lock(); | ||
| #else | ||
| bool contended = true; | ||
| if (lock_.try_lock()) | ||
| contended = false; | ||
| else | ||
| lock_.lock(); | ||
| owner_ = std::this_thread::get_id(); | ||
| ++count_acquired_; | ||
| if (contended) | ||
| ++count_contended_; | ||
| #endif | ||
| } | ||
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| bool | ||
| mutex_dbg_owned::try_lock() | ||
| { | ||
| #ifdef NDEBUG | ||
| return lock_.try_lock(); | ||
| #else | ||
| if (lock_.try_lock()) { | ||
| owner_ = std::this_thread::get_id(); | ||
| return true; | ||
| } | ||
| return false; | ||
| #endif | ||
| } | ||
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| void | ||
| mutex_dbg_owned::unlock() | ||
| { | ||
| #ifndef NDEBUG | ||
| owner_ = std::thread::id(); // id() creates a no-thread sentinel value. | ||
| #endif | ||
| lock_.unlock(); | ||
| } | ||
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| // This query should only be called when the lock is required to be held | ||
| // as it is racy when the lock is not held. | ||
| bool | ||
| mutex_dbg_owned::owned_by_cur_thread() | ||
| { | ||
| return owner_ == std::this_thread::get_id(); | ||
| } | ||
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| // These statistics only count lock(): they do *not* count try_lock() | ||
| // (we could count try_lock with std::atomic on count_contended). | ||
| int64_t | ||
| mutex_dbg_owned::get_count_acquired() | ||
| { | ||
| return count_acquired_; | ||
| } | ||
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| int64_t | ||
| mutex_dbg_owned::get_count_contended() | ||
| { | ||
| return count_contended_; | ||
| } | ||
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| } // namespace drmemtrace | ||
| } // namespace dynamorio |
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