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 172558a6275658f79f706900e48a45d60351dff1..ef99eb782bbb6b19d6e0c6780ef3b73f8f9c8b4e 100644 (file)
--- 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;