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Extend packfile in increments of page_size.

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This improves performance by reducing the number of I/O operations.
This commit is contained in:
Chris Hescock 2016-12-29 11:47:52 -05:00
parent 42864e5842
commit c7a1535f32
1 changed files with 24 additions and 1 deletions
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25
src/indexer.c
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@ -477,13 +477,29 @@ static int write_at(git_indexer *idx, const void *data, git_off_t offset, size_t
static int append_to_pack(git_indexer *idx, const void *data, size_t size)
{
git_off_t new_size;
size_t mmap_alignment;
size_t page_offset;
git_off_t page_start;
git_off_t current_size = idx->pack->mwf.size;
int fd = idx->pack->mwf.fd;
int error;
if (!size)
return 0;
if (p_lseek(fd, current_size + size - 1, SEEK_SET) < 0 ||
if ((error = git__mmap_alignment(&mmap_alignment)) < 0)
return error;
/* Write a single byte to force the file system to allocate space now or
* report an error, since we can't report errors when writing using mmap.
* Round the size up to the nearest page so that we only need to perform file
* I/O when we add a page, instead of whenever we write even a single byte. */
new_size = current_size + size;
page_offset = new_size % mmap_alignment;
page_start = new_size - page_offset;
if (p_lseek(fd, page_start + mmap_alignment - 1, SEEK_SET) < 0 ||
p_write(idx->pack->mwf.fd, data, 1) < 0) {
giterr_set(GITERR_OS, "cannot extend packfile '%s'", idx->pack->pack_name);
return -1;
@ -1041,6 +1057,13 @@ int git_indexer_commit(git_indexer *idx, git_transfer_progress *stats)
goto on_error;
git_mwindow_free_all(&idx->pack->mwf);
/* Truncate file to undo rounding up to next page_size in append_to_pack */
if (p_ftruncate(idx->pack->mwf.fd, idx->pack->mwf.size) < 0) {
giterr_set(GITERR_OS, "failed to truncate pack file '%s'", idx->pack->pack_name);
return -1;
}
/* We need to close the descriptor here so Windows doesn't choke on commit_at */
if (p_close(idx->pack->mwf.fd) < 0) {
giterr_set(GITERR_OS, "failed to close packfile");