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Reuse an output file if exists

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This commit is contained in:
Rui Ueyama 2020-11-09 17:38:12 +09:00
parent 1011b6534d
commit 94b582eb91
1 changed files with 12 additions and 48 deletions
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60
main.cc
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@ -639,19 +639,19 @@ static void fix_synthetic_symbols(ArrayRef<OutputChunk *> output_chunks) {
}
}
static std::pair<u8 *, int> open_output_file(u64 filesize) {
int fd = open(config.output.str().c_str(), O_RDWR | O_CREAT | O_TRUNC, 0777);
static u8 *open_output_file(u64 filesize) {
int fd = open(config.output.str().c_str(), O_RDWR | O_CREAT, 0777);
if (fd == -1)
error("cannot open " + config.output + ": " + strerror(errno));
fallocate(fd, 0, 0, filesize);
if (ftruncate(fd, filesize))
error("ftruncate");
u8 *buf = (u8 *)mmap(nullptr, filesize, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
void *buf = mmap(nullptr, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buf == MAP_FAILED)
error(config.output + ": mmap failed: " + strerror(errno));
return {buf, fd};
close(fd);
return (u8 *)buf;
}
static void write_symtab(u8 *buf, std::vector<ObjectFile *> files) {
@ -776,36 +776,6 @@ int main(int argc, char **argv) {
});
}
u64 prealloc_size = 0;
if (struct stat st; stat(config.output.str().c_str(), &st) == 0)
prealloc_size = st.st_size * 1.2;
sys::fs::remove(config.output);
u8 *buf = nullptr;
int output_fd = -1;
if (prealloc_size)
std::tie(buf, output_fd) = open_output_file(prealloc_size);
// Prefaulting an output file
std::atomic_bool run_prefetch = ATOMIC_VAR_INIT(true);
tbb::task_group prefetch_tg;
if (buf) {
prefetch_tg.run([&]() {
MyTimer t("prefault");
u64 i = 0;
for (; run_prefetch && i < prealloc_size; i += PAGE_SIZE) {
u8 x = buf[i];
auto *loc = (std::atomic_uint8_t *)(buf + i);
while (!std::atomic_compare_exchange_strong(loc, &x, x));
}
llvm::outs() << "prefetcher progress: "
<< (i / PAGE_SIZE) << "/" << (prealloc_size / PAGE_SIZE)
<< "\n";
});
}
Timer total_timer("total", "total");
total_timer.startTimer();
@ -980,8 +950,11 @@ int main(int argc, char **argv) {
}
// Create an output file
if (!buf)
std::tie(buf, output_fd) = open_output_file(prealloc_size);
u8 *buf;
{
MyTimer t("open_file", before_copy);
buf = open_output_file(filesize);
}
// Copy input sections to the output file
{
@ -1009,19 +982,10 @@ int main(int argc, char **argv) {
write_merged_strings(buf, files);
}
// Stop prefetcher
if (buf) {
MyTimer t("wait_prefetcher", before_copy);
run_prefetch = false;
prefetch_tg.wait();
}
// Commit
{
MyTimer t("commit", copy);
munmap(buf, filesize);
ftruncate(output_fd, filesize);
close(output_fd);
}
total_timer.stopTimer();