From 4e33d8677a17c40dd77488ba317cbf5f3431869c Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Sun, 11 Oct 2009 23:35:10 +0200
Subject: [PATCH] [OPTIM] stats: check free space before trying to print

This alone makes a typical HTML stats dump consume 10% CPU less,
because we avoid doing complex printf calls to drop them later.
Only a few common cases have been checked, those which are very
likely to run for nothing.
---
 include/proto/buffers.h |  8 ++++++++
 src/dumpstats.c         | 15 ++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/include/proto/buffers.h b/include/proto/buffers.h
index 801ea1a1d1..6f10553b0e 100644
--- a/include/proto/buffers.h
+++ b/include/proto/buffers.h
@@ -288,6 +288,14 @@ static inline int buffer_contig_space(struct buffer *buf)
 	return ret;
 }
 
+/* Return 1 if the buffer has less than 1/4 of its capacity free, otherwise 0 */
+static inline int buffer_almost_full(struct buffer *buf)
+{
+	if (buffer_contig_space(buf) < buf->size / 4)
+		return 1;
+	return 0;
+}
+
 /*
  * Return the max amount of bytes that can be read from the buffer at once.
  * Note that this may be lower than the actual buffer length when the data
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 6d42b41279..5e7312f671 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -540,6 +540,12 @@ void stats_io_handler(struct stream_interface *si)
 			break;
 		}
 		else if (si->st0 == STAT_CLI_GETREQ) {
+			/* ensure we have some output room left in the event we
+			 * would want to return some info right after parsing.
+			 */
+			if (buffer_almost_full(si->ib))
+				break;
+
 			reql = buffer_si_peekline(si->ob, trash, sizeof(trash));
 			if (reql <= 0) { /* closed or EOL not found */
 				if (reql == 0)
@@ -1121,6 +1127,8 @@ int stats_dump_http(struct session *s, struct buffer *rep, struct uri_auth *uri)
 	case DATA_ST_LIST:
 		/* dump proxies */
 		while (s->data_ctx.stats.px) {
+			if (buffer_almost_full(rep))
+				return 0;
 			px = s->data_ctx.stats.px;
 			/* skip the disabled proxies and non-networked ones */
 			if (px->state != PR_STSTOPPED && (px->cap & (PR_CAP_FE | PR_CAP_BE)))
@@ -1329,6 +1337,9 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri)
 	case DATA_ST_PX_LI:
 		/* stats.l has been initialized above */
 		for (; s->data_ctx.stats.l != NULL; s->data_ctx.stats.l = l->next) {
+			if (buffer_almost_full(rep))
+				return 0;
+
 			l = s->data_ctx.stats.l;
 			if (!l->counters)
 				continue;
@@ -1418,9 +1429,11 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri)
 	case DATA_ST_PX_SV:
 		/* stats.sv has been initialized above */
 		for (; s->data_ctx.stats.sv != NULL; s->data_ctx.stats.sv = sv->next) {
-
 			int sv_state; /* 0=DOWN, 1=going up, 2=going down, 3=UP, 4,5=NOLB, 6=unchecked */
 
+			if (buffer_almost_full(rep))
+				return 0;
+
 			sv = s->data_ctx.stats.sv;
 
 			if (s->data_ctx.stats.flags & STAT_BOUND) {
-- 
2.47.2