linux-kernel - [PATCH v1 4/7] tools lib api: Minor strbuf

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Message-Id: <20230110222003.1591436-5-irogers@google.com>
Date:   Tue, 10 Jan 2023 14:20:00 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Nicolas Schier <nicolas@...sle.eu>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Christy Lee <christylee@...com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Leo Yan <leo.yan@...aro.org>,
        Yang Jihong <yangjihong1@...wei.com>,
        Qi Liu <liuqi115@...wei.com>,
        James Clark <james.clark@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Rob Herring <robh@...nel.org>, Xin Gao <gaoxin@...rlc.com>,
        Zechuan Chen <chenzechuan1@...wei.com>,
        Jason Wang <wangborong@...rlc.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Stephane Eranian <eranian@...gle.com>,
        German Gomez <german.gomez@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        bpf@...r.kernel.org, llvm@...ts.linux.dev
Cc:     Ian Rogers <irogers@...gle.com>
Subject: [PATCH v1 4/7] tools lib api: Minor strbuf_read improvements

If a read is smaller than the remaining space, don't grow the buffer
as it is likely we've reached the end of the file.  Make the grow
amounts a single page rather than just over 2 once the null terminator
is included.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/lib/api/strbuf.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tools/lib/api/strbuf.c b/tools/lib/api/strbuf.c
index 4639b2d02e62..eafa2c01f46a 100644
--- a/tools/lib/api/strbuf.c
+++ b/tools/lib/api/strbuf.c
@@ -143,25 +143,28 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, ssize_t hint)
 	size_t oldalloc = sb->alloc;
 	int ret;
 
-	ret = strbuf_grow(sb, hint ? hint : 8192);
+	ret = strbuf_grow(sb, hint ? hint : 4095);
 	if (ret)
 		return ret;
 
 	for (;;) {
-		ssize_t cnt;
+		ssize_t read_size;
+		size_t sb_remaining = sb->alloc - sb->len - 1;
 
-		cnt = read(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
-		if (cnt < 0) {
+		read_size = read(fd, sb->buf + sb->len, sb_remaining);
+		if (read_size < 0) {
 			if (oldalloc == 0)
 				strbuf_release(sb);
 			else
 				strbuf_setlen(sb, oldlen);
-			return cnt;
+			return read_size;
 		}
-		if (!cnt)
+		if (read_size == 0)
 			break;
-		sb->len += cnt;
-		ret = strbuf_grow(sb, 8192);
+		sb->len += read_size;
+		if ((size_t)read_size < sb_remaining)
+			continue;
+		ret = strbuf_grow(sb, 4095);
 		if (ret)
 			return ret;
 	}
-- 
2.39.0.314.g84b9a713c41-goog