Commit 72f04b50 authored Mar 28, 2017 by Zhou Chengming Committed by Jiri Kosina Mar 30, 2017

livepatch: Reduce the time of finding module symbols



It's reported that the time of insmoding a klp.ko for one of our
out-tree modules is too long.

~ time sudo insmod klp.ko
real	0m23.799s
user	0m0.036s
sys	0m21.256s

Then we found the reason: our out-tree module used a lot of static local
variables, so klp.ko has a lot of relocation records which reference the
module. Then for each such entry klp_find_object_symbol() is called to
resolve it, but this function uses the interface kallsyms_on_each_symbol()
even for finding module symbols, so will waste a lot of time on walking
through vmlinux kallsyms table many times.

This patch changes it to use module_kallsyms_on_each_symbol() for modules
symbols. After we apply this patch, the sys time reduced dramatically.

~ time sudo insmod klp.ko
real	0m1.007s
user	0m0.032s
sys	0m0.924s

Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Jessica Yu <jeyu@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

parent c1ae3cfa

kernel/livepatch/core.c

+4 −1

Original line number	Original line	Diff line number	Diff line
	@@ -182,6 +182,9 @@ static int klp_find_object_symbol(const char objname, const char name,
	};		};

	mutex_lock(&module_mutex);		mutex_lock(&module_mutex);
			if (objname)
			module_kallsyms_on_each_symbol(klp_find_callback, &args);
			else
	kallsyms_on_each_symbol(klp_find_callback, &args);		kallsyms_on_each_symbol(klp_find_callback, &args);
	mutex_unlock(&module_mutex);		mutex_unlock(&module_mutex);

Admin message