[patch] pax-utils patch to use mmap MAP_SHARED instead of MAP_PRIVATE

_readelf_fd-try-MAP_SHARED.patch (text/plain), 1.22 KB, created by Zac Medico on 2020-10-17 10:11:13 UTC

From f518c51be88f5fb50d6741801c244c64e035ae54 Mon Sep 17 00:00:00 2001
From: Zac Medico <[e-mail]>
Date: Sat, 17 Oct 2020 02:36:36 -0700
Subject: [PATCH] _readelf_fd: try MAP_SHARED to see if it performs better than
 MAP_PRIVATE

Bug 749624 reports that scanelf has a slow performance problem
when processing large numbers of non-elf files which are backed
by some form of slow network storage. It may be that the
performance problem it due to mmap usage in the _readelf_fd,
therefore try MAP_SHARED to see if it performs better than
MAP_PRIVATE for this slow network storage scenario.

Bug: https://bugs.gentoo.org/749624
---
 paxelf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/paxelf.c b/paxelf.c
index bbd38bf..de0a9ff 100644
--- a/paxelf.c
+++ b/paxelf.c
@@ -676,7 +676,7 @@ elfobj *_readelf_fd(const char *filename, int fd, size_t len, int read_only)
 			return NULL;
 	}
 
-	buffer = mmap(0, len, PROT_READ | (read_only ? 0 : PROT_WRITE), (read_only ? MAP_PRIVATE : MAP_SHARED), fd, 0);
+	buffer = mmap(0, len, PROT_READ | (read_only ? 0 : PROT_WRITE), MAP_SHARED, fd, 0);
 	if (buffer == MAP_FAILED) {
 		warn("mmap on '%s' of %li bytes failed :(", filename, (unsigned long)len);
 		return NULL;
-- 
2.26.2