There are only three places where the log buffer lock is not already
held when the reader lock is taken:
1) In LogReader, when a new reader connects
2) In LogReader, when a misbehaving reader disconnects
3) LogReaderThread::ThreadFunction()
1) and 2) happen sufficiently rarely that there's no impact if they
additionally held a global lock.
3) is refactored in this CL. Previously, it would do the below in a loop
1) Lock the reader lock then wait on a condition variable
2) Unlock the reader lock
3) Lock the log buffer lock in LogBuffer::FlushTo()
4) In each iteration in the LogBuffer::FlushTo() loop
1) Lock then unlock the reader lock in FilterSecondPass()
2) Unlock the log buffer lock to send the message, then re-lock it
5) Unlock the log buffer lock when leaving LogBuffer::FlushTo()
If these locks are collapsed into a single lock, then this simplifies to:
1) Lock the single lock then wait on a condition variable
2) In each iteration in the LogBuffer::FlushTo() loop
1) Unlock the single lock to send the message, then re-lock it
Collapsing both these locks into a single lock simplifes the code and
removes the overhead of acquiring the second lock, in the majority of
use cases where the first lock is already held.
Secondly, this lock will be a plain std::mutex instead of a RwLock.
RwLock's are appropriate when there is a substantial imbalance between
readers and writers and high contention, neither are true for logd.
Bug: 169736426
Test: logging unit tests
Change-Id: Ia511506f2d0935a5321c1b2f65569066f91ecb06
Also generic syntax clean up and removing some unused aspects (sorting
the list and the TODO increasing performance based on this sorting).
Test: logging unit tests
Change-Id: I56bb3866c13cb4c28bd48665bf32ec620cf0278e
Clear() and Prune() return a boolean indicating whether or not their
operations failed because the log buffer was 'busy'. This means that
they return false upon success and true upon failure, which is not
intuitive.
This change inverts their return value to simply be true if they were
successful or false otherwise. It also simplifies the return value of
ChattyLogBuffer::Prune() to true if the requested number of rows have
been pruned or if all rows in the log buffer have been pruned, and
otherwise return false.
Test: logging unit tests
Test: clearing works even under logging pressure
Change-Id: I346bb945496ef62bf8e973298f81c5163f49bc57
We can use libbase logging to output to the kernel log instead of the
'prdebug' function, so use that instead.
Bonus #1: we can now use CHECK().
Bonus #2: logging unit tests automatically output to stderr.
Bonus #3: We see dependent library's logs instead of losing them to
the void.
Test: logging unit tests
Test: logs show appropriately in dmesg / stderr
Test: CHECK() works
Change-Id: I92f8056b4820dc4998996cf46460568085299700
Other log buffers may not use LogBufferElement, so we should decouple
the two classes. This uses an intermediate LogStatisticsElement
structs instead of passing a large number of parameters to each
function.
This additionally moves IsBinary() and the GetTag() functions out into
LogUtils.h since they can be used generically by other users.
Test: logging unit tests
Change-Id: I71f53257342c067bcccd5aa00bae47f714cd7c66
This is required for tests that are aware of sequence numbers to pass;
each new LogBuffer instance should start from sequence = 1, which
isn't the case if the current sequence number is a static.
Test: unit tests
Change-Id: Ie488f8ac5e22b946b7e6237d1d5caf14929c0ec3
This saves 4 or 8 bytes off of each log message for 32 bit or 64 bit
devices respectively. In practice, this actually saves more, due to
avoiding heap fragmentation.
Averaging over 5 runs of the LogBufferTest.random_messages unit test
(32 bit), this change results in 8k less memory used when 1000 logs
are logged and results in 260k less memory used when 10000 logs are
logged.
Test: check memory usage during LogBufferTest.random_messages
Test: logging unit tests
Change-Id: Ia7953e3c4cb19631ef43bab1deb91bb336bc2520
This code and comment is hard to follow, despite the operation being
simple, so refactor the code to be easier to follow.
Also, use std::unique_ptr instead of raw pointers as appropriate.
Test: logging unit tests
Change-Id: Id1f29f4deeca730d1e3b6856e1581d0b840f883e
Fix a subtle bug that liblog event messages have a payload of int32_t,
not uint32_t, so they should only be summed to int32_t max.
Make a bunch of test improvements as well to support these.
Test: these tests
Change-Id: I4069cc546240bfffec5b19f34ebec913799674e8
One of the reasons that logcat and logd statically include liblog is
to access the symbols in log_time.cpp, which we do not expose
otherwise. Except for strptime(), which will be handled in a separate
CL, these symbols are either small enough to inline in the header or
unused and can be removed.
Test: logging unit tests
Change-Id: I1f8cfbb779aef79fc7d5b6d0050438fe5f0e0e2c
In the future, we'll want to be able to write to outputs that are not
necessarily a libsysutils SocketClient, for example host tests of
LogBuffer. Therefore, we add a LogWriter class to be used instead of
SocketClient.
Test: logging unit tests
Change-Id: I4385be65e14e83a635691a7ba79e9bf060e49484
We may use different implementations of LogBuffer in the future, so we
make it interface and create a concrete ChattyLogBuffer class that
implements it.
Test: logging unit tests
Change-Id: I5731d6404640664c9acc26b7c677dff3110c6a11
