## Problem
When the build ids of the profile and binary do not match, the error
reported by llvm-profdata is `no entries in callstack map after
symbolization`, but the root cause of this problem is the **build id
mismatch**.
## Trigger scenario
For example, when performing `memprof` optimization on `clang`,
`rawprofile` is collected through `ninja clang`. In addition to running
clang, some other programs will also be executed, and these programs
will also generate rawprofile. When `no entries in callstack map after
symbolization` appears during `llvm-profdata merge`, users may
mistakenly think that the **instrumentation failed or other reasons**,
and will **not directly realize that the binary and profile do not
match**.
## Changed
Currently, when the build id does not match, an assert error is
triggered only in debug mode. Change it to directly return an error when
the build id does not match.
We can use *Set::insert_range to collapse:
for (auto Elem : Range)
Set.insert(E.first);
down to:
Set.insert_range(llvm::make_first_range(Range));
In some cases, we can further fold that into the set declaration.
Collect profiles for functions we encounter when collecting a contextual profile, that are not associated with a call site. This is expected to happen for signal handlers, but it also - problematically - currently happens for mem{memset|copy|move|set}, which are currently inserted after profile instrumentation.
Collecting a "regular" flat profile in these cases would hide the problem - that we loose better profile opportunities.
When we collect a contextual profile, we sample the threads entering its root and only collect on one at a time (see `ContextRoot::Taken`). If we want to compare profiles between contextual profiles, and/or flat profiles, we have a problem: we don't know how to compare the counter values relative to each other. To that end, we add `ContextRoot::TotalEntries`, which is incremented every time a root is entered and serves as multiplier for the counter values collected under that root.
We expose this in the profile and leave the normalization to the user of the profile, for a few reasons:
* it's only needed if reasoning about all profiles in aggregate.
* the goal, in compiler_rt, is to flush out the profile as quickly as possible, and performing multiplications adds an overhead that may not even be necessary if the consumer of the profile doesn't care about combining profiles
* the information itself may be interesting as an indication of relative sampling of various contexts.
* Added YAML traits for `CallSiteInfo`
* Updated the `MemProfReader` to pass `Frames` instead of the entire
`CallSiteInfo`
* Updated test cases to use `testing::Field`
* Add YAML sequence traits for CallSiteInfo in MemProfYAML
* Also extend IndexedMemProfRecord
* XFAIL the MemProfYaml round trip test until we update the profile
format
For now we only read and write the additional information from the YAML
format. The YAML round trip test will be enabled when the serialized format is updated.
A section for flat profiles (i.e. non-contextual). This is useful for debugging or for intentional cases where a root isn't identified.
This patch adds the reader/writer support. `compiler-rt` changes follow in a subsequent change.
The module currently stores the target triple as a string. This means
that any code that wants to actually use the triple first has to
instantiate a Triple, which is somewhat expensive. The change in #121652
caused a moderate compile-time regression due to this. While it would be
easy enough to work around, I think that architecturally, it makes more
sense to store the parsed Triple in the module, so that it can always be
directly queried.
For this change, I've opted not to add any magic conversions between
std::string and Triple for backwards-compatibilty purses, and instead
write out needed Triple()s or str()s explicitly. This is because I think
a decent number of them should be changed to work on Triple as well, to
avoid unnecessary conversions back and forth.
The only interesting part in this patch is that the default triple is
Triple("") instead of Triple() to preserve existing behavior. The former
defaults to using the ELF object format instead of unknown object
format. We should fix that as well.
The profile format has now a separate section called "Contexts" - there will be a corresponding one for flat profiles. The root has a separate tag because, in addition to not having a callsite ID as all the other context nodes have under it, it will have additional fields in subsequent patches.
The rest of this patch amounts to a bit of refactorings in the reader/writer (for better reuse later) and tests fixups.
Fix a build speed regression due to repeated reading of profile
metadata. Before the function `readFuncMetadata(ProfileHasAttribute,
Profiles)` reads the metadata for all the functions(`Profiles`),
however, it's actually used for on-demand loading, it can be called for
multiple times, which leads to redundant reading that causes the build
speed regression. Now fix it to read the metadata only for the new
loaded functions(functions in the `FuncsToUse`).
DefaultCutoffsData does not have an entry for the 0th percentile. As a
result, when the getEntryForPercentile method is called with a
percentile argument of 0, it returns a ProfileSummaryEntry for the 1st
percentile instead. This behavior affects the threshold calculations,
such as getHotCountThreshold, causing them to incorrectly identify some
sample profile counts as hot when they should not be.
This patch addresses the issue by handling the 0th percentile case in
the getEntryForPercentile method. This ensures that when the
-profile-summary-cutoff-hot (or -cold) option is set to 0, no sample
counts are treated as hot (or all sample counts are treated as cold).
When iterating over function records, filtered by file name, currently,
the iteration goes over all the function records, repeatedly for each
source file, essentially giving quadratic behavior.
413647d730972eac9675f695c2ea63fb393a5531 sped up some cases by keeping
track of the indices of the function records corresponding to each file
name. This change expands the use of that map to FunctionRecordIterator.
On a test case with Firefox's libxul.so and a 2.5MB profile, this brings
down the runtime of `llvm-cov export $lib --instr-profile $prof -t lcov`
from 12 minutes with 90% spent in skipOtherFiles to 19 seconds with no
samples in skipOtherFiles at all under a sampling profiler (with a
sampling interval of 1ms).
Fixes#62079
This is a follow-up from PR #122545, which enabled converting yaml to contextual profiles.
This change uses the lower level yaml APIs because:
- the mapping APIs `llvm::yaml` offers don't work with `const` values, because they (the APIs) want to enable both serialization and deserialization
- building a helper data structure would be an alternative, but it'd be either memory-consuming or overly-complex design, given the recursive nature of the contextual profiles.
We have a textual representation of contextual profiles for test scenarios, mainly. This patch moves that to YAML instead of JSON. YAML is more succinct and readable (some of the .ll tests should be illustrative). In addition, JSON is parse-able by the YAML reader.
A subsequent patch will address deserialization.
(thanks, @kazutakahirata, for showing me how to use the llvm YAML reader/writer APIs, which I incorrectly thought to be more low-level than the JSON ones!)
The result of "Independence pairs" is not mergeable. This change makes
defers re-calculation of "Independence pairs" after merging test
vectors.
No apparent behavior changes.
This patch makes sure YAML files are opened for reading as text file to
trigger auto-conversion from EBCDIC encoding into expected ASCII
encoding on z/OS platform. This is required to fix the following lit
tests:
```
LLVM :: tools/llvm-gsymutil/ARM_AArch64/macho-gsym-callsite-info-exe.yaml
LLVM :: tools/llvm-gsymutil/ARM_AArch64/macho-gsym-callsite-info-obj.test
LLVM :: tools/llvm-gsymutil/ARM_AArch64/macho-gsym-callsite-info-dsym.yaml
LLVM :: Transforms/PGOProfile/memprof_undrift_missing_leaf.ll
```
Now that IndexedMemProfData::{addFrame,addCallStack} are the only
callers of Frame::hash and hashCallStack, respectively, this patch
moves those functions into IndexedMemProfData and makes them private.
With this patch, we can obtain FrameId and CallStackId only through
addFrame and addCallStack, respectively.
This patch adds YAML read/write support to llvm-profdata. The primary
intent is to accommodate MemProf profiles in test cases, thereby
avoiding the binary format.
The read support is via llvm-profdata merge. This is useful when we
want to verify that the compiler does the right thing on a given .ll
file and a MemProf profile in a test case. In the test case, we would
convert the MemProf profile in YAML to an indexed profile and invoke
the compiler on the .ll file along with the indexed profile.
The write support is via llvm-profdata show --memory. This is useful
when we wish to convert an indexed MemProf profile to YAML while
writing tests. We would compile a test case in C++, run it for an
indexed MemProf profile, and then convert it to the text format.
This patch adds a helper function to replace an idiom like:
CallStackId CSId = hashCallStack(CallStack)
MemProfData.CallStacks.try_emplace(CSId, CallStack);
// Do something with CSId.
The patch makes InstrProfWriter::writeImpl less monolithic by adding
InstrProfWriter::writeBinaryIds to serialize binary IDs. This way,
InstrProfWriter::writeImpl can simply call the new function instead of
handling all the details within writeImpl.
This patch extends the PGO infrastructure with an option to prefer the
instrumentation of loop entry blocks.
This option is a generalization of
19fb5b467b,
and helps to cover cases where the loop exit is never executed.
An example where this can occur are event handling loops.
Note that change does NOT change the default behavior.
Now that MemProf format version 1 has been removed, nobody uses:
- IndexedAllocationInfo::CallStack
- IndexedMemProfRecord::CallSites
This patch removed the dead struct fields.
You might notice that IndexedMemProfRecord::{clear,merge} do not
mention CallSiteIds at all. I think it's an oversight. clear doesn't
matter at the moment because we call it during serialization to reduce
memory footprint. merge is simply not as well tested as it should be.
I'll follow up with a separate patch to address these issues.
This patch adds YAML-based deserialization for MemProf profile.
It's been painful to write tests for MemProf passes because we do not
have a text format for the MemProf profile. We would write a test
case in C++, run it for a binary MemProf profile, and then finally run
a test written in LLVM IR with the binary profile.
This patch paves the way toward YAML-based MemProf profile.
Specifically, it adds new class YAMLMemProfReader derived from
MemProfReader. For now, it only adds a function to parse StringRef
pointing to YAML data. Subseqeunt patches will wire it to
llvm-profdata and read from a file.
The field names are based on various printYAML functions in MemProf.h.
I'm not aiming for compatibility with the format used in printYAML,
but I don't see a point in changing the field names.
This iteration works around the unavailability of
ScalarTraits<uintptr_t> on macOS.
This reverts commit c00e53208db638c35499fc80b555f8e14baa35f0.
It looks like this breaks building LLVM on macOS and some other
platform/compiler combos
https://lab.llvm.org/buildbot/#/builders/23/builds/5252https://green.lab.llvm.org/job/llvm.org/job/clang-san-iossim/5356/console
In file included from /Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/lib/ProfileData/MemProfReader.cpp:34:
In file included from /Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/ProfileData/MemProfReader.h:24:
In file included from /Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/ProfileData/InstrProfReader.h:22:
In file included from /Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/ProfileData/InstrProfCorrelator.h:21:
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/Support/YAMLTraits.h:1173:36: error: implicit instantiation of undefined template 'llvm::yaml::MissingTrait<unsigned long>'
char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
^
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/Support/YAMLTraits.h:961:7: note: in instantiation of function template specialization 'llvm::yaml::yamlize<unsigned long>' requested here
yamlize(*this, Val, Required, Ctx);
^
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/Support/YAMLTraits.h:883:11: note: in instantiation of function template specialization 'llvm::yaml::IO::processKey<unsigned long, llvm::yaml::EmptyContext>' requested here
this->processKey(Key, Val, true, Ctx);
^
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/ProfileData/MIBEntryDef.inc:55:1: note: in instantiation of function template specialization 'llvm::yaml::IO::mapRequired<unsigned long>' requested here
MIBEntryDef(AccessHistogram = 27, AccessHistogram, uintptr_t)
^
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/lib/ProfileData/MemProfReader.cpp:77:8: note: expanded from macro 'MIBEntryDef'
Io.mapRequired(KeyStr.str().c_str(), MIB.Name); \
^
/Users/ec2-user/jenkins/workspace/llvm.org/clang-san-iossim/llvm-project/llvm/include/llvm/Support/YAMLTraits.h:310:8: note: template is declared here
struct MissingTrait;
^
1 error generated.
This patch adds YAML-based deserialization for MemProf profile.
It's been painful to write tests for MemProf passes because we do not
have a text format for the MemProf profile. We would write a test
case in C++, run it for a binary MemProf profile, and then finally run
a test written in LLVM IR with the binary profile.
This patch paves the way toward YAML-based MemProf profile.
Specifically, it adds new class YAMLMemProfReader derived from
MemProfReader. For now, it only adds a function to parse StringRef
pointing to YAML data. Subseqeunt patches will wire it to
llvm-profdata and read from a file.
The field names are based on various printYAML functions in MemProf.h.
I'm not aiming for compatibility with the format used in printYAML,
but I don't see a point in changing the field names.
IndexedMemProfRecord contains a complete package of the MemProf
profile, including frames, call stacks, and records. This patch
replaces the three member variables of MemProfReader with
IndexedMemProfRecord.
This transition significantly simplies both the constructor and the
final "take" method:
MemProfReader(IndexedMemProfData MemProfData)
: MemProfData(std::move(MemProfData)) {}
IndexedMemProfData takeMemProfData() { return std::move(MemProfData); }
CallStackRadixTreeBuilder::build takes the parameter
MemProfFrameIndexes by value, involving copies:
std::optional<const llvm::DenseMap<FrameIdTy, LinearFrameId>>
MemProfFrameIndexes
Then "build" makes another copy of MemProfFrameIndexe and passes it to
encodeCallStack for every call stack, which is painfully slow.
This patch changes the type to a pointer so that we don't have to make
a copy every time we pass the argument.
Without this patch, it takes 553 seconds to run "llvm-profdata merge"
on a large MemProf raw profile. This patch shortenes that down to 67
seconds.
This patch adds a quick validity check to
InstrProfWriter::addMemProfData. Specifically, we check to see if we
have all (or none) of the MemProf profile components (frames, call
stacks, records).
The credit goes to Teresa Johnson for suggesting this assert.
This patch removes two functions to verify the consistency between:
- IndexedAllocationInfo::CallStack
- IndexedAllocationInfo::CSId
Now that MemProf format Version 1 has been removed,
IndexedAllocationInfo::CallStack doesn't participate in either
serialization or deserialization, so we don't care about the
consistency between the two fields in IndexAllocationInfo.
Subsequent patches will remove uses of the old field and eventually
remove the field.
This reverts commit fdb050a5024320ec29d2edf3f2bc686c3a84abaa, and
restores ccb4702038900d82d1041ff610788740f5cef723, with a fix for build
bot failures.
Specifically, add ProfileData to the dependences of the BitWriter
library, which was causing shared library builds of LLVM to fail.
Reproduced the failure with a shared library build and confirmed this
change fixes that build failure.
Leverage the support added to represent allocation contexts in a more
compact way via a radix tree in the indexed profile to similarly reduce
sizes of the bitcode summaries.
For a large target, this reduced the size of the per-module summaries by
about 18% and in the distributed combined index files by 28%.
