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Implement GNU jobserver posix client support
The core principle of a jobserver is simple: Before starting a new job (edge in ninja-speak), a token must be acquired from an external entity as approval. Once a job is finished, the token must be returned to signal a free thread. In the case of GNU Make, this external entity is the parent process which has executed ninja and is managing the load capacity for all subprocesses which it has spawned. Introducing client support for this model allows ninja to give load capacity management to this parent process, allowing it to control the number of subprocesses that ninja spawns at any given time. This functionality is desirable when ninja is used as part of a bigger build, such as builds with Yocto/OpenEmbedded, Openwrt/Linux, Buildroot and Android. Here, multiple compile jobs are executed in parallel in order to maximize cpu utilization, but if each compile job uses all available cores, the system is overloaded. This implementation instantiates the client in real_main() and passes references to the class into other classes. All tokens are returned whenever the CommandRunner aborts, and the current number of tokens compared to the current number of running subprocesses controls the available load capacity, used to determine how many new tokens to attempt to acquire in order to start another job for each loop to find work. Co-authored-by: Martin Hundebøll <martin@geanix.com> Signed-off-by: Michael Pratt <mcpratt@pm.me>
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| // Copyright 2024 Google Inc. All Rights Reserved. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| #include "jobserver.h" | ||
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| #include <fcntl.h> | ||
| #include <unistd.h> | ||
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| #include <cassert> | ||
| #include <cstring> | ||
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| #include "util.h" | ||
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| Jobserver::Jobserver() { | ||
| assert(rfd_ < 0); | ||
| assert(wfd_ < 0); | ||
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| // Return early if no makeflags are passed in the environment | ||
| char* makeflags = std::getenv("MAKEFLAGS"); | ||
| if (makeflags == nullptr) { | ||
| return; | ||
| } | ||
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| // Tokenize string to characters in flag_, then words in flags_ | ||
| while (flag_char_ < strlen(makeflags)) { | ||
| while (flag_char_ < strlen(makeflags) && | ||
| !isblank(static_cast<unsigned char>(makeflags[flag_char_]))) { | ||
| flag_.push_back(static_cast<unsigned char>(makeflags[flag_char_])); | ||
| flag_char_++; | ||
| } | ||
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| if (flag_.size() > 0) | ||
| flags_.push_back(flag_); | ||
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| flag_.clear(); | ||
| flag_char_++; | ||
| } | ||
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| // Search for --jobserver-auth | ||
| for (size_t n = 0; n < flags_.size(); n++) | ||
| if (flags_[n].find(AUTH_KEY) == 0) | ||
| flag_ = flags_[n].substr(strlen(AUTH_KEY)); | ||
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| // Fallback to --jobserver-fds | ||
| if (flag_.empty()) | ||
| for (size_t n = 0; n < flags_.size(); n++) | ||
| if (flags_[n].find(FDS_KEY) == 0) | ||
| flag_ = flags_[n].substr(strlen(FDS_KEY)); | ||
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| jobserver_name_.assign(flag_); | ||
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| const char* jobserver = jobserver_name_.c_str(); | ||
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| // Return early if the flag's value is empty | ||
| if (jobserver_name_.empty()) { | ||
| Warning("invalid jobserver value: '%s'", jobserver); | ||
| return; | ||
| } | ||
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| jobserver_fifo_ = jobserver_name_.find(FIFO_KEY) == 0 ? true : false; | ||
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| // Return early if jobserver type is unknown (neither fifo nor pipe) | ||
| if (!jobserver_fifo_ && sscanf(jobserver, "%d,%d", &rfd_, &wfd_) != 2) { | ||
| Warning("invalid jobserver value: '%s'", jobserver); | ||
| return; | ||
| } | ||
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| if (jobserver_fifo_) { | ||
| rfd_ = open(jobserver + strlen(FIFO_KEY), O_RDONLY | O_NONBLOCK); | ||
| wfd_ = open(jobserver + strlen(FIFO_KEY), O_WRONLY); | ||
| } | ||
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| if (rfd_ == -1 || wfd_ == -1) | ||
| Fatal("failed to open jobserver: %s: %s", | ||
| jobserver, errno ? strerror(errno) : "Bad file descriptor"); | ||
| else if (rfd_ > 0 && wfd_ > 0) | ||
| Info("using jobserver: %s", jobserver); | ||
| else | ||
| Fatal("Make provided an invalid pipe: %s (mark the command as recursive)", | ||
| jobserver); | ||
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| // Signal that we have initialized but do not have a token yet | ||
| token_count_ = -1; | ||
| } | ||
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| Jobserver::~Jobserver() { | ||
| Clear(); | ||
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| if (rfd_ >= 0) | ||
| close(rfd_); | ||
| if (wfd_ >= 0) | ||
| close(wfd_); | ||
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| rfd_ = -1; | ||
| wfd_ = -1; | ||
| } | ||
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| bool Jobserver::Enabled() const { | ||
| return rfd_ >= 0 && wfd_ >= 0; | ||
| } | ||
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| int Jobserver::Tokens() const { | ||
| return token_count_; | ||
| } | ||
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| bool Jobserver::Acquire() { | ||
| // The first token is implicitly handed to a process | ||
| if (token_count_ <= 0) { | ||
| token_count_ = 1; | ||
| return true; | ||
| } | ||
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| char token; | ||
| int ret = read(rfd_, &token, 1); | ||
| if (ret < 0 && errno != EAGAIN && errno != EWOULDBLOCK) { | ||
| if (!jobserver_fifo_) | ||
| Warning("Make closed the pipe: %d (mark the command as recursive)", rfd_); | ||
| Fatal("failed to read token from jobserver: %d: %s", rfd_, strerror(errno)); | ||
| } | ||
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| if (ret > 0) | ||
| token_count_++; | ||
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| return ret > 0; | ||
| } | ||
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| void Jobserver::Release() { | ||
| if (token_count_ < 0) | ||
| token_count_ = 0; | ||
| if (token_count_ > 0) | ||
| token_count_--; | ||
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| // The first token is implicitly handed to a process | ||
| if (token_count_ == 0) | ||
| return; | ||
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| char token = '+'; | ||
| int ret = write(wfd_, &token, 1); | ||
| if (ret != 1) { | ||
| if (!jobserver_fifo_) | ||
| Warning("Make closed the pipe: %d (mark the command as recursive)", wfd_); | ||
| Fatal("failed to return token to jobserver: %d: %s", rfd_, strerror(errno)); | ||
| } | ||
| } | ||
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| void Jobserver::Clear() { | ||
| while (token_count_) | ||
| Release(); | ||
| } |
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