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logd: always wake 'wrapped' readers on prune 

See the comment in the code for more details.  'wrapped' readers are
uncommon and error prone, and this change makes them more reliable.
Its side effect is that wrapped readers will wake more often, but
they'll still be batched to a large degree.

Bug: 163617910
Test: logging unit tests
Test: logcat --wrap does the right thing
Change-Id: I4b6f8331ff7854787c97f821b2a5bf8d7da321c6
This commit is contained in:
Tom Cherry 2020-08-12 09:44:52 -07:00
parent 0df0fcbb9d
commit d0e8451d59
1 changed files with 10 additions and 6 deletions
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16
logd/SerializedLogBuffer.cpp
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@ -143,9 +143,16 @@ bool SerializedLogBuffer::Prune(log_id_t log_id, size_t bytes_to_free, uid_t uid
if (!reader_thread->IsWatching(log_id)) {
continue;
}
if (!oldest || oldest->start() > reader_thread->start() ||
(oldest->start() == reader_thread->start() &&
reader_thread->deadline().time_since_epoch().count() != 0)) {
if (reader_thread->deadline().time_since_epoch().count() != 0) {
// Always wake up wrapped readers when pruning. 'Wrapped' readers are an optimization
// that allows the reader to wait until logs starting at a specified time stamp are
// about to be pruned. This is error-prone however, since if that timestamp is about to
// be pruned, the reader is not likely to read the messages fast enough to not back-up
// logd. Instead, we can achieve an nearly-as-efficient but not error-prune batching
// effect by waking the reader whenever any chunk is about to be pruned.
reader_thread->triggerReader_Locked();
}
if (!oldest || oldest->start() > reader_thread->start()) {
oldest = reader_thread.get();
}
}
@ -202,9 +209,6 @@ void SerializedLogBuffer::KickReader(LogReaderThread* reader, log_id_t id, size_
LOG(WARNING) << "Kicking blocked reader, " << reader->name()
<< ", from LogBuffer::kickMe()";
reader->release_Locked();
} else if (reader->deadline().time_since_epoch().count() != 0) {
// Allow a blocked WRAP deadline reader to trigger and start reporting the log data.
reader->triggerReader_Locked();
} else {
// Tell slow reader to skip entries to catch up.
unsigned long prune_rows = bytes_to_free / 300;