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vcs: hook sysfs devices into object lifetime instead of "binding"

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During bootup performance tracing I noticed many occurrences of
vca* device creation and removal, leading to the usual userspace
uevent processing, which are, in this case, rather pointless.

A simple test showing the kernel timing (not including all the
work userspace has to do), gives us these numbers:
  $ time for i in `seq 1000`; do echo a > /dev/tty2; done
  real    0m1.142s
  user    0m0.015s
  sys     0m0.540s

If we move the hook for the vcs* driver core devices from the
tty "binding" to the vc allocation/deallocation, which is what
the vcs* devices represent, we get the following numbers:
  $ time for i in `seq 1000`; do echo a > /dev/tty2; done
  real    0m0.152s
  user    0m0.030s
  sys     0m0.072s

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Kay Sievers
2009-03-09 14:18:52 +01:00
committed by Greg Kroah-Hartman
parent ce21c7bcd7
commit 4995f8ef9d
3 changed files with 13 additions and 12 deletions
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16
drivers/char/vc_screen.c
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@@ -479,18 +479,18 @@ static const struct file_operations vcs_fops = {
static struct class *vc_class;
void vcs_make_sysfs(struct tty_struct *tty)
void vcs_make_sysfs(int index)
{
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 1), NULL,
"vcs%u", tty->index + 1);
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, tty->index + 129), NULL,
"vcsa%u", tty->index + 1);
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
"vcs%u", index + 1);
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
"vcsa%u", index + 1);
}
void vcs_remove_sysfs(struct tty_struct *tty)
void vcs_remove_sysfs(int index)
{
device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 1));
device_destroy(vc_class, MKDEV(VCS_MAJOR, tty->index + 129));
device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
}
int __init vcs_init(void)