Re: voluntary-preempt-2.6.8.1-P9 : big latency when logging on console

Ingo Molnar
2004-08-30T09:39:45Z

* P.O. Gaillard <pierre-olivier.gaillard@fr.thalesgroup.com> wrote:

> Hello,
>
> I have a 1.6ms latency every time I log in with P9.

could you try the patch below, ontop of P9? (or ontop of the latest, -Q5
patch)

The problem with font loading is that vt_ioctl runs with the BKL held
(as all ioctls) which disables preemption, but in this case it seems
pretty safe to drop the lock - the vga console has its own spinlock.

Ingo

--- linux/drivers/video/console/vgacon.c.orig
+++ linux/drivers/video/console/vgacon.c
@@ -763,6 +763,7 @@ static int vgacon_do_font_op(struct vgas
charmap += 4 * cmapsz;
#endif

+ unlock_kernel();
spin_lock_irq(&vga_lock);
/* First, the Sequencer */
vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x1);
@@ -848,6 +849,7 @@ static int vgacon_do_font_op(struct vgas
vga_wattr(state->vgabase, VGA_AR_ENABLE_DISPLAY, 0);
}
spin_unlock_irq(&vga_lock);
+ lock_kernel();
return 0;
}