From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Fri, 28 Feb 2025 16:27:12 +0000 (+0100)
Subject: shared: improve strbuf_reserve_extra performance
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b4f1546bd388ca4c97b23af5c8e50a567aeec155;p=thirdparty%2Fkmod.git

shared: improve strbuf_reserve_extra performance

If strbuf is used (depmod, modprobe -c) then strbuf_reserve_extra is
performance critical. This reduces amount of instructions for
modprobe -c by around 10 %, the total instruction count for depmod
by 1 % (majority is within reading module files).

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/296
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/shared/strbuf.c b/shared/strbuf.c
index 172558a6..ef99eb78 100644
--- a/shared/strbuf.c
+++ b/shared/strbuf.c
@@ -36,12 +36,12 @@ static bool buf_realloc(struct strbuf *buf, size_t sz)
 
 static bool strbuf_reserve_extra(struct strbuf *buf, size_t n)
 {
+	if (n < buf->size - buf->used)
+		return true;
+
 	if (uaddsz_overflow(buf->used, n, &n) || n >= SIZE_MAX - BUF_STEP)
 		return false;
 
-	if (n < buf->size)
-		return true;
-
 	if (++n % BUF_STEP)
 		n = ((n / BUF_STEP) + 1) * BUF_STEP;