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#include "cache.h"
#include "config.h"
#include "entry.h"
#include "parallel-checkout.h"
#include "pkt-line.h"
#include "progress.h"
#include "run-command.h"
#include "sigchain.h"
#include "streaming.h"
#include "thread-utils.h"
#include "trace2.h"
struct pc_worker {
struct child_process cp;
size_t next_item_to_complete, nr_items_to_complete;
};
struct parallel_checkout {
enum pc_status status;
struct parallel_checkout_item *items; /* The parallel checkout queue. */
size_t nr, alloc;
struct progress *progress;
unsigned int *progress_cnt;
};
static struct parallel_checkout parallel_checkout;
enum pc_status parallel_checkout_status(void)
{
return parallel_checkout.status;
}
static const int DEFAULT_THRESHOLD_FOR_PARALLELISM = 100;
static const int DEFAULT_NUM_WORKERS = 1;
void get_parallel_checkout_configs(int *num_workers, int *threshold)
{
char *env_workers = getenv("GIT_TEST_CHECKOUT_WORKERS");
if (env_workers && *env_workers) {
if (strtol_i(env_workers, 10, num_workers)) {
die(_("invalid value for '%s': '%s'"),
"GIT_TEST_CHECKOUT_WORKERS", env_workers);
}
if (*num_workers < 1)
*num_workers = online_cpus();
*threshold = 0;
return;
}
if (git_config_get_int("checkout.workers", num_workers))
*num_workers = DEFAULT_NUM_WORKERS;
else if (*num_workers < 1)
*num_workers = online_cpus();
if (git_config_get_int("checkout.thresholdForParallelism", threshold))
*threshold = DEFAULT_THRESHOLD_FOR_PARALLELISM;
}
void init_parallel_checkout(void)
{
if (parallel_checkout.status != PC_UNINITIALIZED)
BUG("parallel checkout already initialized");
parallel_checkout.status = PC_ACCEPTING_ENTRIES;
}
static void finish_parallel_checkout(void)
{
if (parallel_checkout.status == PC_UNINITIALIZED)
BUG("cannot finish parallel checkout: not initialized yet");
free(parallel_checkout.items);
memset(&parallel_checkout, 0, sizeof(parallel_checkout));
}
static int is_eligible_for_parallel_checkout(const struct cache_entry *ce,
const struct conv_attrs *ca)
{
enum conv_attrs_classification c;
size_t packed_item_size;
/*
* Symlinks cannot be checked out in parallel as, in case of path
* collision, they could racily replace leading directories of other
* entries being checked out. Submodules are checked out in child
* processes, which have their own parallel checkout queues.
*/
if (!S_ISREG(ce->ce_mode))
return 0;
packed_item_size = sizeof(struct pc_item_fixed_portion) + ce->ce_namelen +
(ca->working_tree_encoding ? strlen(ca->working_tree_encoding) : 0);
/*
* The amount of data we send to the workers per checkout item is
* typically small (75~300B). So unless we find an insanely huge path
* of 64KB, we should never reach the 65KB limit of one pkt-line. If
* that does happen, we let the sequential code handle the item.
*/
if (packed_item_size > LARGE_PACKET_DATA_MAX)
return 0;
c = classify_conv_attrs(ca);
switch (c) {
case CA_CLASS_INCORE:
return 1;
case CA_CLASS_INCORE_FILTER:
/*
* It would be safe to allow concurrent instances of
* single-file smudge filters, like rot13, but we should not
* assume that all filters are parallel-process safe. So we
* don't allow this.
*/
return 0;
case CA_CLASS_INCORE_PROCESS:
/*
* The parallel queue and the delayed queue are not compatible,
* so they must be kept completely separated. And we can't tell
* if a long-running process will delay its response without
* actually asking it to perform the filtering. Therefore, this
* type of filter is not allowed in parallel checkout.
*
* Furthermore, there should only be one instance of the
* long-running process filter as we don't know how it is
* managing its own concurrency. So, spreading the entries that
* requisite such a filter among the parallel workers would
* require a lot more inter-process communication. We would
* probably have to designate a single process to interact with
* the filter and send all the necessary data to it, for each
* entry.
*/
return 0;
case CA_CLASS_STREAMABLE:
return 1;
default:
BUG("unsupported conv_attrs classification '%d'", c);
}
}
int enqueue_checkout(struct cache_entry *ce, struct conv_attrs *ca,
int *checkout_counter)
{
struct parallel_checkout_item *pc_item;
if (parallel_checkout.status != PC_ACCEPTING_ENTRIES ||
!is_eligible_for_parallel_checkout(ce, ca))
return -1;
ALLOC_GROW(parallel_checkout.items, parallel_checkout.nr + 1,
parallel_checkout.alloc);
pc_item = &parallel_checkout.items[parallel_checkout.nr];
pc_item->ce = ce;
memcpy(&pc_item->ca, ca, sizeof(pc_item->ca));
pc_item->status = PC_ITEM_PENDING;
pc_item->id = parallel_checkout.nr;
pc_item->checkout_counter = checkout_counter;
parallel_checkout.nr++;
return 0;
}
size_t pc_queue_size(void)
{
return parallel_checkout.nr;
}
static void advance_progress_meter(void)
{
if (parallel_checkout.progress) {
(*parallel_checkout.progress_cnt)++;
display_progress(parallel_checkout.progress,
*parallel_checkout.progress_cnt);
}
}
static int handle_results(struct checkout *state)
{
int ret = 0;
size_t i;
int have_pending = 0;
/*
* We first update the successfully written entries with the collected
* stat() data, so that they can be found by mark_colliding_entries(),
* in the next loop, when necessary.
*/
for (i = 0; i < parallel_checkout.nr; i++) {
struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];
if (pc_item->status == PC_ITEM_WRITTEN)
update_ce_after_write(state, pc_item->ce, &pc_item->st);
}
for (i = 0; i < parallel_checkout.nr; i++) {
struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];
switch(pc_item->status) {
case PC_ITEM_WRITTEN:
if (pc_item->checkout_counter)
(*pc_item->checkout_counter)++;
break;
case PC_ITEM_COLLIDED:
/*
* The entry could not be checked out due to a path
* collision with another entry. Since there can only
* be one entry of each colliding group on the disk, we
* could skip trying to check out this one and move on.
* However, this would leave the unwritten entries with
* null stat() fields on the index, which could
* potentially slow down subsequent operations that
* require refreshing it: git would not be able to
* trust st_size and would have to go to the filesystem
* to see if the contents match (see ie_modified()).
*
* Instead, let's pay the overhead only once, now, and
* call checkout_entry_ca() again for this file, to
* have its stat() data stored in the index. This also
* has the benefit of adding this entry and its
* colliding pair to the collision report message.
* Additionally, this overwriting behavior is consistent
* with what the sequential checkout does, so it doesn't
* add any extra overhead.
*/
ret |= checkout_entry_ca(pc_item->ce, &pc_item->ca,
state, NULL,
pc_item->checkout_counter);
advance_progress_meter();
break;
case PC_ITEM_PENDING:
have_pending = 1;
/* fall through */
case PC_ITEM_FAILED:
ret = -1;
break;
default:
BUG("unknown checkout item status in parallel checkout");
}
}
if (have_pending)
error("parallel checkout finished with pending entries");
return ret;
}
static int reset_fd(int fd, const char *path)
{
if (lseek(fd, 0, SEEK_SET) != 0)
return error_errno("failed to rewind descriptor of '%s'", path);
if (ftruncate(fd, 0))
return error_errno("failed to truncate file '%s'", path);
return 0;
}
static int write_pc_item_to_fd(struct parallel_checkout_item *pc_item, int fd,
const char *path)
{
int ret;
struct stream_filter *filter;
struct strbuf buf = STRBUF_INIT;
char *blob;
size_t size;
ssize_t wrote;
/* Sanity check */
assert(is_eligible_for_parallel_checkout(pc_item->ce, &pc_item->ca));
filter = get_stream_filter_ca(&pc_item->ca, &pc_item->ce->oid);
if (filter) {
if (stream_blob_to_fd(fd, &pc_item->ce->oid, filter, 1)) {
/* On error, reset fd to try writing without streaming */
if (reset_fd(fd, path))
return -1;
} else {
return 0;
}
}
blob = read_blob_entry(pc_item->ce, &size);
if (!blob)
return error("cannot read object %s '%s'",
oid_to_hex(&pc_item->ce->oid), pc_item->ce->name);
/*
* checkout metadata is used to give context for external process
* filters. Files requiring such filters are not eligible for parallel
* checkout, so pass NULL. Note: if that changes, the metadata must also
* be passed from the main process to the workers.
*/
ret = convert_to_working_tree_ca(&pc_item->ca, pc_item->ce->name,
blob, size, &buf, NULL);
if (ret) {
size_t newsize;
free(blob);
blob = strbuf_detach(&buf, &newsize);
size = newsize;
}
wrote = write_in_full(fd, blob, size);
free(blob);
if (wrote < 0)
return error("unable to write file '%s'", path);
return 0;
}
static int close_and_clear(int *fd)
{
int ret = 0;
if (*fd >= 0) {
ret = close(*fd);
*fd = -1;
}
return ret;
}
void write_pc_item(struct parallel_checkout_item *pc_item,
struct checkout *state)
{
unsigned int mode = (pc_item->ce->ce_mode & 0100) ? 0777 : 0666;
int fd = -1, fstat_done = 0;
struct strbuf path = STRBUF_INIT;
const char *dir_sep;
strbuf_add(&path, state->base_dir, state->base_dir_len);
strbuf_add(&path, pc_item->ce->name, pc_item->ce->ce_namelen);
dir_sep = find_last_dir_sep(path.buf);
/*
* The leading dirs should have been already created by now. But, in
* case of path collisions, one of the dirs could have been replaced by
* a symlink (checked out after we enqueued this entry for parallel
* checkout). Thus, we must check the leading dirs again.
*/
if (dir_sep && !has_dirs_only_path(path.buf, dir_sep - path.buf,
state->base_dir_len)) {
pc_item->status = PC_ITEM_COLLIDED;
trace2_data_string("pcheckout", NULL, "collision/dirname", path.buf);
goto out;
}
fd = open(path.buf, O_WRONLY | O_CREAT | O_EXCL, mode);
if (fd < 0) {
if (errno == EEXIST || errno == EISDIR) {
/*
* Errors which probably represent a path collision.
* Suppress the error message and mark the item to be
* retried later, sequentially. ENOTDIR and ENOENT are
* also interesting, but the above has_dirs_only_path()
* call should have already caught these cases.
*/
pc_item->status = PC_ITEM_COLLIDED;
trace2_data_string("pcheckout", NULL,
"collision/basename", path.buf);
} else {
error_errno("failed to open file '%s'", path.buf);
pc_item->status = PC_ITEM_FAILED;
}
goto out;
}
if (write_pc_item_to_fd(pc_item, fd, path.buf)) {
/* Error was already reported. */
pc_item->status = PC_ITEM_FAILED;
close_and_clear(&fd);
unlink(path.buf);
goto out;
}
fstat_done = fstat_checkout_output(fd, state, &pc_item->st);
if (close_and_clear(&fd)) {
error_errno("unable to close file '%s'", path.buf);
pc_item->status = PC_ITEM_FAILED;
goto out;
}
if (state->refresh_cache && !fstat_done && lstat(path.buf, &pc_item->st) < 0) {
error_errno("unable to stat just-written file '%s'", path.buf);
pc_item->status = PC_ITEM_FAILED;
goto out;
}
pc_item->status = PC_ITEM_WRITTEN;
out:
strbuf_release(&path);
}
static void send_one_item(int fd, struct parallel_checkout_item *pc_item)
{
size_t len_data;
char *data, *variant;
struct pc_item_fixed_portion *fixed_portion;
const char *working_tree_encoding = pc_item->ca.working_tree_encoding;
size_t name_len = pc_item->ce->ce_namelen;
size_t working_tree_encoding_len = working_tree_encoding ?
strlen(working_tree_encoding) : 0;
/*
* Any changes in the calculation of the message size must also be made
* in is_eligible_for_parallel_checkout().
*/
len_data = sizeof(struct pc_item_fixed_portion) + name_len +
working_tree_encoding_len;
data = xmalloc(len_data);
fixed_portion = (struct pc_item_fixed_portion *)data;
fixed_portion->id = pc_item->id;
fixed_portion->ce_mode = pc_item->ce->ce_mode;
fixed_portion->crlf_action = pc_item->ca.crlf_action;
fixed_portion->ident = pc_item->ca.ident;
fixed_portion->name_len = name_len;
fixed_portion->working_tree_encoding_len = working_tree_encoding_len;
/*
* We pad the unused bytes in the hash array because, otherwise,
* Valgrind would complain about passing uninitialized bytes to a
* write() syscall. The warning doesn't represent any real risk here,
* but it could hinder the detection of actual errors.
*/
oidcpy_with_padding(&fixed_portion->oid, &pc_item->ce->oid);
variant = data + sizeof(*fixed_portion);
if (working_tree_encoding_len) {
memcpy(variant, working_tree_encoding, working_tree_encoding_len);
variant += working_tree_encoding_len;
}
memcpy(variant, pc_item->ce->name, name_len);
packet_write(fd, data, len_data);
free(data);
}
static void send_batch(int fd, size_t start, size_t nr)
{
size_t i;
sigchain_push(SIGPIPE, SIG_IGN);
for (i = 0; i < nr; i++)
send_one_item(fd, &parallel_checkout.items[start + i]);
packet_flush(fd);
sigchain_pop(SIGPIPE);
}
static struct pc_worker *setup_workers(struct checkout *state, int num_workers)
{
struct pc_worker *workers;
int i, workers_with_one_extra_item;
size_t base_batch_size, batch_beginning = 0;
ALLOC_ARRAY(workers, num_workers);
for (i = 0; i < num_workers; i++) {
struct child_process *cp = &workers[i].cp;
child_process_init(cp);
cp->git_cmd = 1;
cp->in = -1;
cp->out = -1;
cp->clean_on_exit = 1;
strvec_push(&cp->args, "checkout--worker");
if (state->base_dir_len)
strvec_pushf(&cp->args, "--prefix=%s", state->base_dir);
if (start_command(cp))
die("failed to spawn checkout worker");
}
base_batch_size = parallel_checkout.nr / num_workers;
workers_with_one_extra_item = parallel_checkout.nr % num_workers;
for (i = 0; i < num_workers; i++) {
struct pc_worker *worker = &workers[i];
size_t batch_size = base_batch_size;
/* distribute the extra work evenly */
if (i < workers_with_one_extra_item)
batch_size++;
send_batch(worker->cp.in, batch_beginning, batch_size);
worker->next_item_to_complete = batch_beginning;
worker->nr_items_to_complete = batch_size;
batch_beginning += batch_size;
}
return workers;
}
static void finish_workers(struct pc_worker *workers, int num_workers)
{
int i;
/*
* Close pipes before calling finish_command() to let the workers
* exit asynchronously and avoid spending extra time on wait().
*/
for (i = 0; i < num_workers; i++) {
struct child_process *cp = &workers[i].cp;
if (cp->in >= 0)
close(cp->in);
if (cp->out >= 0)
close(cp->out);
}
for (i = 0; i < num_workers; i++) {
int rc = finish_command(&workers[i].cp);
if (rc > 128) {
/*
* For a normal non-zero exit, the worker should have
* already printed something useful to stderr. But a
* death by signal should be mentioned to the user.
*/
error("checkout worker %d died of signal %d", i, rc - 128);
}
}
free(workers);
}
static inline void assert_pc_item_result_size(int got, int exp)
{
if (got != exp)
BUG("wrong result size from checkout worker (got %dB, exp %dB)",
got, exp);
}
static void parse_and_save_result(const char *buffer, int len,
struct pc_worker *worker)
{
struct pc_item_result *res;
struct parallel_checkout_item *pc_item;
struct stat *st = NULL;
if (len < PC_ITEM_RESULT_BASE_SIZE)
BUG("too short result from checkout worker (got %dB, exp >=%dB)",
len, (int)PC_ITEM_RESULT_BASE_SIZE);
res = (struct pc_item_result *)buffer;
/*
* Worker should send either the full result struct on success, or
* just the base (i.e. no stat data), otherwise.
*/
if (res->status == PC_ITEM_WRITTEN) {
assert_pc_item_result_size(len, (int)sizeof(struct pc_item_result));
st = &res->st;
} else {
assert_pc_item_result_size(len, (int)PC_ITEM_RESULT_BASE_SIZE);
}
if (!worker->nr_items_to_complete)
BUG("received result from supposedly finished checkout worker");
if (res->id != worker->next_item_to_complete)
BUG("unexpected item id from checkout worker (got %"PRIuMAX", exp %"PRIuMAX")",
(uintmax_t)res->id, (uintmax_t)worker->next_item_to_complete);
worker->next_item_to_complete++;
worker->nr_items_to_complete--;
pc_item = &parallel_checkout.items[res->id];
pc_item->status = res->status;
if (st)
pc_item->st = *st;
if (res->status != PC_ITEM_COLLIDED)
advance_progress_meter();
}
static void gather_results_from_workers(struct pc_worker *workers,
int num_workers)
{
int i, active_workers = num_workers;
struct pollfd *pfds;
CALLOC_ARRAY(pfds, num_workers);
for (i = 0; i < num_workers; i++) {
pfds[i].fd = workers[i].cp.out;
pfds[i].events = POLLIN;
}
while (active_workers) {
int nr = poll(pfds, num_workers, -1);
if (nr < 0) {
if (errno == EINTR)
continue;
die_errno("failed to poll checkout workers");
}
for (i = 0; i < num_workers && nr > 0; i++) {
struct pc_worker *worker = &workers[i];
struct pollfd *pfd = &pfds[i];
if (!pfd->revents)
continue;
if (pfd->revents & POLLIN) {
int len = packet_read(pfd->fd, packet_buffer,
sizeof(packet_buffer), 0);
if (len < 0) {
BUG("packet_read() returned negative value");
} else if (!len) {
pfd->fd = -1;
active_workers--;
} else {
parse_and_save_result(packet_buffer,
len, worker);
}
} else if (pfd->revents & POLLHUP) {
pfd->fd = -1;
active_workers--;
} else if (pfd->revents & (POLLNVAL | POLLERR)) {
die("error polling from checkout worker");
}
nr--;
}
}
free(pfds);
}
static void write_items_sequentially(struct checkout *state)
{
size_t i;
for (i = 0; i < parallel_checkout.nr; i++) {
struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];
write_pc_item(pc_item, state);
if (pc_item->status != PC_ITEM_COLLIDED)
advance_progress_meter();
}
}
int run_parallel_checkout(struct checkout *state, int num_workers, int threshold,
struct progress *progress, unsigned int *progress_cnt)
{
int ret;
if (parallel_checkout.status != PC_ACCEPTING_ENTRIES)
BUG("cannot run parallel checkout: uninitialized or already running");
parallel_checkout.status = PC_RUNNING;
parallel_checkout.progress = progress;
parallel_checkout.progress_cnt = progress_cnt;
if (parallel_checkout.nr < num_workers)
num_workers = parallel_checkout.nr;
if (num_workers <= 1 || parallel_checkout.nr < threshold) {
write_items_sequentially(state);
} else {
struct pc_worker *workers = setup_workers(state, num_workers);
gather_results_from_workers(workers, num_workers);
finish_workers(workers, num_workers);
}
ret = handle_results(state);
finish_parallel_checkout();
return ret;
}