linux-kernel - [RFC 11/12] module: use list_add_tail

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Date:   Fri, 10 Mar 2023 21:17:11 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, david@...hat.com, petr.pavlu@...e.com,
        prarit@...hat.com
Cc:     christophe.leroy@...roup.eu, song@...nel.org, mcgrof@...nel.org,
        torvalds@...ux-foundation.org
Subject: [RFC 11/12] module: use list_add_tail_rcu() when adding module

Put a new module at the end of the list intead of making
new modules at the top of the list. find_module_all() start
the hunt using the first entry on the list, if we assume
that the modules which are first loaded are the most
frequently looked for modules this should provide a tiny
optimization.

This is theoretical, and could use more actual data by analzying
the impact of this patch on boot time a slew of systems using
systemd-analyze.

Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 kernel/module/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 909454f9616e..bc9202b60d55 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2608,7 +2608,7 @@ static int add_unformed_module(struct module *mod)
 		goto out;

 	mod_update_bounds(mod);
-	list_add_rcu(&mod->list, &modules);
+	list_add_tail_rcu(&mod->list, &modules);
 	mod_tree_insert(mod);
 	err = 0;

-- 
2.39.1