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From 98237819a417bf81a393b893e84c76ddb6dd36f5 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Fri, 19 Mar 2021 20:38:22 +0000
Subject: [PATCH] use buffered stdio
Our generation of HTML triggers many small write(2) syscalls
which is inefficient.
Time output on a horrible query against my git.git mirror
shows significant performance improvement:
QUERY_STRING='id=2b93bfac0f5bcabbf60f174f4e7bfa9e318e64d5&id2=d6da71a9d16b8cf27f9d8f90692d3625c849cbc8'
PATH_INFO=/mirrors/git.git/diff
export QUERY_STRING PATH_INFO
time ./cgit >/dev/null
Before:
real 0m1.585s
user 0m0.904s
sys 0m0.658s
After:
real 0m0.750s
user 0m0.666s
sys 0m0.076s
Signed-off-by: Eric Wong <e@80x24.org>
Message-Id: <20210319203822.GA30217@dcvr>
---
cache.c | 7 +++++++
cgit.c | 2 +-
filter.c | 22 +++++++++++++++++++++-
html.c | 2 +-
ui-snapshot.c | 3 +++
5 files changed, 33 insertions(+), 3 deletions(-)
diff --git a/cache.c b/cache.c
index 2c70be78..580c0e80 100644
--- a/cache.c
+++ b/cache.c
@@ -265,6 +265,13 @@ static int process_slot(struct cache_slot *slot)
{
int err;
+ /*
+ * Make sure any buffered data is flushed before we redirect,
+ * do sendfile(2) or write(2)
+ */
+ if (fflush(stdout))
+ return errno;
+
err = open_slot(slot);
if (!err && slot->match) {
if (is_expired(slot)) {
diff --git a/cgit.c b/cgit.c
index c4320f04..d8ea2212 100644
--- a/cgit.c
+++ b/cgit.c
@@ -674,7 +674,7 @@ static inline void authenticate_post(void)
len = MAX_AUTHENTICATION_POST_BYTES;
if ((len = read(STDIN_FILENO, buffer, len)) < 0)
die_errno("Could not read POST from stdin");
- if (write(STDOUT_FILENO, buffer, len) < 0)
+ if (fwrite(buffer, 1, len, stdout) < len)
die_errno("Could not write POST to stdout");
cgit_close_filter(ctx.cfg.auth_filter);
exit(0);
diff --git a/filter.c b/filter.c
index 70f5b749..fba26aa0 100644
--- a/filter.c
+++ b/filter.c
@@ -48,6 +48,7 @@ static int open_exec_filter(struct cgit_filter *base, va_list ap)
for (i = 0; i < filter->base.argument_count; i++)
filter->argv[i + 1] = va_arg(ap, char *);
+ chk_zero(fflush(stdout), "unable to flush STDOUT");
filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
"Unable to duplicate STDOUT");
chk_zero(pipe(pipe_fh), "Unable to create pipe to subprocess");
@@ -71,6 +72,7 @@ static int close_exec_filter(struct cgit_filter *base)
struct cgit_exec_filter *filter = (struct cgit_exec_filter *)base;
int i, exit_status = 0;
+ chk_zero(fflush(stdout), "unable to flush STDOUT");
chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
"Unable to restore STDOUT");
close(filter->old_stdout);
@@ -143,17 +145,32 @@ void cgit_init_filters(void)
#endif
#ifndef NO_LUA
-static ssize_t (*libc_write)(int fd, const void *buf, size_t count);
+static size_t (*libc_fwrite)(const void *buf, size_t size, size_t n, FILE *);
+static ssize_t (*libc_write)(int fd, const void *buf, size_t size);
static ssize_t (*filter_write)(struct cgit_filter *base, const void *buf, size_t count) = NULL;
static struct cgit_filter *current_write_filter = NULL;
void cgit_init_filters(void)
{
+ /*
+ * we need to wrap both functions since the Lua filter may
+ * have code which calls write(2) directly, bypassing fwrite(3)
+ */
+ libc_fwrite = dlsym(RTLD_NEXT, "fwrite");
+ if (!libc_fwrite)
+ die("Could not locate libc's write function");
libc_write = dlsym(RTLD_NEXT, "write");
if (!libc_write)
die("Could not locate libc's write function");
}
+size_t fwrite(const void *buf, size_t size, size_t n, FILE *f)
+{
+ if (f != stdout || !filter_write)
+ return libc_fwrite(buf, size, n, f);
+ return filter_write(current_write_filter, buf, size * n);
+}
+
ssize_t write(int fd, const void *buf, size_t count)
{
if (fd != STDOUT_FILENO || !filter_write)
@@ -305,6 +322,9 @@ static int open_lua_filter(struct cgit_filter *base, va_list ap)
struct lua_filter *filter = (struct lua_filter *)base;
int i;
+ if (fflush(stdout))
+ return 1;
+
if (init_lua_filter(filter))
return 1;
diff --git a/html.c b/html.c
index 138c649e..ca9db91d 100644
--- a/html.c
+++ b/html.c
@@ -80,7 +80,7 @@ char *fmtalloc(const char *format, ...)
void html_raw(const char *data, size_t size)
{
- if (write(STDOUT_FILENO, data, size) != size)
+ if (fwrite(data, 1, size, stdout) != size)
die_errno("write error on html output");
}
diff --git a/ui-snapshot.c b/ui-snapshot.c
index 556d3ed4..8b81e374 100644
--- a/ui-snapshot.c
+++ b/ui-snapshot.c
@@ -37,6 +37,9 @@ static int write_archive_type(const char *format, const char *hex, const char *p
/* argv_array guarantees a trailing NULL entry. */
memcpy(nargv, argv.argv, sizeof(char *) * (argv.argc + 1));
+ if (fflush(stdout))
+ return errno;
+
result = write_archive(argv.argc, nargv, NULL, the_repository, NULL, 0);
argv_array_clear(&argv);
free(nargv);
--
2.32.0
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