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fileops: stat() before open()ing in git_futils_readbuffer_updated()

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This reverts refactoring done in 13224ea4aa
that introduces a performance regression for NFS when reading files that
don't exist. open() forces a cache invalidation on NFS, while stat()ing a
file just uses the cache and is very quick.

To give a specific example, say you have a repo with a thousand packed
refs. Before this change, looking up every single one ould incur a thousand
slow open() calls. With this change, it's a thousand fast stat() calls.
This commit is contained in:
Brodie Rao 2013-08-13 10:55:37 -07:00
parent 14da618260
commit 9ccdb21155
1 changed files with 12 additions and 5 deletions
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17
src/fileops.c
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@ -147,6 +147,7 @@ int git_futils_readbuffer_fd(git_buf *buf, git_file fd, size_t len)
int git_futils_readbuffer_updated(
git_buf *buf, const char *path, time_t *mtime, size_t *size, int *updated)
{
int error = 0;
git_file fd;
struct stat st;
bool changed = false;
@ -156,11 +157,15 @@ int git_futils_readbuffer_updated(
if (updated != NULL)
*updated = 0;
if ((fd = git_futils_open_ro(path)) < 0)
return fd;
if (p_stat(path, &st) < 0) {
error = errno;
giterr_set(GITERR_OS, "Failed to stat '%s'", path);
if (error == ENOENT || error == ENOTDIR)
return GIT_ENOTFOUND;
return -1;
}
if (p_fstat(fd, &st) < 0 || S_ISDIR(st.st_mode) || !git__is_sizet(st.st_size+1)) {
p_close(fd);
if (S_ISDIR(st.st_mode) || !git__is_sizet(st.st_size+1)) {
giterr_set(GITERR_OS, "Invalid regular file stat for '%s'", path);
return -1;
}
@ -177,7 +182,6 @@ int git_futils_readbuffer_updated(
changed = true;
if (!changed) {
p_close(fd);
return 0;
}
@ -186,6 +190,9 @@ int git_futils_readbuffer_updated(
if (size != NULL)
*size = (size_t)st.st_size;
if ((fd = git_futils_open_ro(path)) < 0)
return fd;
if (git_futils_readbuffer_fd(buf, fd, (size_t)st.st_size) < 0) {
p_close(fd);
return -1;