[PATCH v4 2/2] fs/proc: sysctl: optimize register single one ctl_table

Meng Tang
2022-03-03T07:09:19Z

Sysctls are being moved out of kernel/sysctl.c and out to
their own respective subsystems / users to help with easier
maintance and avoid merge conflicts. But when we move just
one entry and to its own new file the last entry for this
new file must be empty, so we are essentialy bloating the
kernel one extra empty entry per each newly moved sysctl.

To help with this, I have added support for registering just
one ctl_table, therefore not bloating the kernel when we
move a single ctl_table to its own file.

The optimization has been implemented in the previous patch,
here use register_sysctl_single() to register single one
ctl_table.

In this modification, I counted the size changes of each
object file during the compilation process.

When there is no strip, size changes are as follows:
before now save space
fs/dcache.o 904936 904760 176bytes
fs/exec.o 883584 883440 144bytes
fs/namespace.o 1614776 1614616 160bytes
fs/notify/dnotify/dnotify.o 255992 255872 120bytes
init/do_mounts_initrd.o 296552 296392 160bytes
kernel/acct.o 459184 459032 152bytes
kernel/delayacct.o 208680 208536 144bytes
kernel/kprobes.o 794968 794936 32bytes
kernel/panic.o 367696 367560 136bytes

When there is exec with 'strip -d', size changes are as follows:
before now save space
fs/dcache.o 79040 78952 88bytes
fs/exec.o 57960 57864 96bytes
fs/namespace.o 111904 111824 80bytes
fs/notify/dnotify/dnotify.o 8816 8736 80bytes
init/do_mounts_initrd.o 4872 4760 112bytes
kernel/acct.o 18104 18000 104bytes
kernel/delayacct.o 8768 8664 104bytes
kernel/kprobes.o 63192 63104 88bytes
kernel/panic.o 26760 26672 88bytes

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Meng Tang <tangmeng@uniontech.com>
---
fs/dcache.c | 5 ++---
fs/exec.c | 5 ++---
fs/namespace.c | 5 ++---
fs/notify/dnotify/dnotify.c | 5 ++---
init/do_mounts_initrd.c | 5 ++---
kernel/acct.c | 5 ++---
kernel/delayacct.c | 5 ++---
kernel/kprobes.c | 5 ++---
kernel/panic.c | 5 ++---
9 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index c84269c6e8bf..29fed2df79d1 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -190,13 +190,12 @@ static struct ctl_table fs_dcache_sysctls[] = {
.maxlen = 6*sizeof(long),
.mode = 0444,
.proc_handler = proc_nr_dentry,
- },
- { }
+ }
};

static int __init init_fs_dcache_sysctls(void)
{
- register_sysctl_init("fs", fs_dcache_sysctls);
+ register_sysctl_single("fs", fs_dcache_sysctls);
return 0;
}
fs_initcall(init_fs_dcache_sysctls);
diff --git a/fs/exec.c b/fs/exec.c
index c2586b791b87..58e9e50b9d98 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -2140,13 +2140,12 @@ static struct ctl_table fs_exec_sysctls[] = {
.proc_handler = proc_dointvec_minmax_coredump,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
- },
- { }
+ }
};

static int __init init_fs_exec_sysctls(void)
{
- register_sysctl_init("fs", fs_exec_sysctls);
+ register_sysctl_single("fs", fs_exec_sysctls);
return 0;
}

diff --git a/fs/namespace.c b/fs/namespace.c
index df172818e1f8..1384fa7f8c79 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4673,13 +4673,12 @@ static struct ctl_table fs_namespace_sysctls[] = {
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
- },
- { }
+ }
};

static int __init init_fs_namespace_sysctls(void)
{
- register_sysctl_init("fs", fs_namespace_sysctls);
+ register_sysctl_single("fs", fs_namespace_sysctls);
return 0;
}
fs_initcall(init_fs_namespace_sysctls);
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 829dd4a61b66..813a22825be5 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -28,12 +28,11 @@ static struct ctl_table dnotify_sysctls[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
- },
- {}
+ }
};
static void __init dnotify_sysctl_init(void)
{
- register_sysctl_init("fs", dnotify_sysctls);
+ register_sysctl_single("fs", dnotify_sysctls);
}
#else
#define dnotify_sysctl_init() do { } while (0)
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 327962ea354c..d37f24959aa3 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -28,13 +28,12 @@ static struct ctl_table kern_do_mounts_initrd_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
- },
- { }
+ }
};

static __init int kernel_do_mounts_initrd_sysctls_init(void)
{
- register_sysctl_init("kernel", kern_do_mounts_initrd_table);
+ register_sysctl_single("kernel", kern_do_mounts_initrd_table);
return 0;
}
late_initcall(kernel_do_mounts_initrd_sysctls_init);
diff --git a/kernel/acct.c b/kernel/acct.c
index 62200d799b9b..c628808c9213 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -83,13 +83,12 @@ static struct ctl_table kern_acct_table[] = {
.maxlen = 3*sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
- },
- { }
+ }
};

static __init int kernel_acct_sysctls_init(void)
{
- register_sysctl_init("kernel", kern_acct_table);
+ register_sysctl_single("kernel", kern_acct_table);
return 0;
}
late_initcall(kernel_acct_sysctls_init);
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 2c1e18f7c5cf..6b776cbcb559 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -73,13 +73,12 @@ static struct ctl_table kern_delayacct_table[] = {
.proc_handler = sysctl_delayacct,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
- },
- { }
+ }
};

static __init int kernel_delayacct_sysctls_init(void)
{
- register_sysctl_init("kernel", kern_delayacct_table);
+ register_sysctl_single("kernel", kern_delayacct_table);
return 0;
}
late_initcall(kernel_delayacct_sysctls_init);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 94cab8c9ce56..1cf54662e2ed 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -970,13 +970,12 @@ static struct ctl_table kprobe_sysctls[] = {
.proc_handler = proc_kprobes_optimization_handler,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
- },
- {}
+ }
};

static void __init kprobe_sysctls_init(void)
{
- register_sysctl_init("debug", kprobe_sysctls);
+ register_sysctl_single("debug", kprobe_sysctls);
}
#endif /* CONFIG_SYSCTL */

diff --git a/kernel/panic.c b/kernel/panic.c
index ae5c0ca86016..90f1a0f25139 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -85,13 +85,12 @@ static struct ctl_table kern_panic_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
- },
- { }
+ }
};

static __init int kernel_panic_sysctls_init(void)
{
- register_sysctl_init("kernel", kern_panic_table);
+ register_sysctl_single("kernel", kern_panic_table);
return 0;
}
late_initcall(kernel_panic_sysctls_init);
--
2.20.1