On Tue 2016-12-13 10:52:37, Sergey Senozhatsky wrote: > On (12/12/16 16:58), Petr Mladek wrote: > > On Thu 2016-12-01 22:55:44, Sergey Senozhatsky wrote: > [..] > > But not really because we report lost messages from both buffers > > and from all CPUs here. > [..] > > The perfect solution would be to remember the number of lost messages > > in struct printk_safe_seq_buf. Then we might bump the value directly > > in printk_safe_log_store() instead of returning the ugly -ENOSPC. > > ok, I can take a look. this won't grow the per-CPU buffers bigger, > but will shrink the actual message buffer size by sizeof(atomic), > not that dramatic.
IMHO, the size is a negligible difference. If we are often getting on the edge of the buffers, we have problems anyway. > * unrelated, can be done later (if ever) * > > speaking of tha actual message buffer size, we, may be, can move > `struct irq_work' out of printk_safe_seq_buf. there is already > a printk-related per-CPU irq_work in place - wake_up_klogd_work. > so we may be can use it, instead of defining a bunch of new irq_works. > this will increase the printk-safe/nmi per-CPU message buffer size > by sizeof(irq_work). Interesting idea! I think that there is a space for more optimization. For example, we will not need to schedule the irq work if we are flushing the per-CPU buffers from irq work and we know that we will flush consoles or wake up the kthread right after that. Also I though about using a global "printk_pending" variable and queue the irqwork only when the given event was not already set. I would leave all this optimization for a later patchset. > > Also we could use an universal message (no "NMI" or "printk-safe") > > because it could be printed right after flushing the messages > > that fit the buffer. > > this "context" part probably can be dropped. both printk-safe and > printk-nmi per-CPU buffer sizes are controlled by a single .config > option anyway; user can't increase the printk-safe buffer size > without increasing the printk-nmi buffer size (in case if printk-safe > buffer is too small). I agree. Best Regards, Petr
