On Wed, Jun 18, 2014 at 11:11:12AM -0700, Davidlohr Bueso wrote:
> On Wed, 2014-06-18 at 04:14 -0700, Luis R. Rodriguez wrote:
> > From: "Luis R. Rodriguez" <mcg...@suse.com>
> > Signed-off-by: Luis R. Rodriguez <mcg...@suse.com>
>
> Looks good Luis, thanks a lot for doing this -- it will definitely help
> my everyday debugging issues on huge machines.
>
> I ran this on my 160-core Westmere. Some nits below, otherwise:
>
> Reviewed-and-tested-by: Davidlohr Bueso <davidl...@hp.com>
Great thanks for testing and your review!
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index af164a7..7c7b599 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -848,12 +849,43 @@ static int __init log_buf_len_setup(char *str)
> > }
> > early_param("log_buf_len", log_buf_len_setup);
> >
> > +static void __init log_buf_add_cpu(void)
> > +{
> > + int cpu_extra;
>
> unsigned int
Amended.
> > +
> > + /*
> > + * archs should set up cpu_possible_bits properly with
> > + * set_cpu_possible() after setup_arch() but just in
> > + * case lets ensure this is valid. During an early
> > + * call before setup_arch()() this will be 1.
> > + */
> > + if (num_possible_cpus() <= 1)
>
> This can never return 0, so how about making it == 1?
I was originally concerned over the early boot code which had
not yet called setup_arch() but since we now have a check for
early on setup_log_buf() before calling log_buf_add_cpu() I
think its safe to check for 1 then, will change! I'll also
remove the note about this always returning 1 on early init
before setup_arch() as I only confirmed that for x86 -- unless
of course there is code that ensures this for early boot for
all archs, I just can't find it.
> > + return;
> > +
> > + cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MIN_BUF_LEN;
> > +
> > + /* by default this will only continue through for large > 64 CPUs */
> > + if (cpu_extra <= __LOG_BUF_LEN / 2)
> > + return;
> > +
> > + pr_info("log_buf_len cpu_extra contribution: %d\n", cpu_extra);
>
> We should add 'bytes' for units.
That should mean also amending the orignal setup_log_buf() for the final size,
will do that too.
> Also, while at it, how about making it easier for users and also print
> the individual contribution of each CPU
Sure, done. While at it I renamed LOG_CPU_MIN_BUF_SHIFT to MAX to annotate folks
want to to consider the worst case scenario to help with debugging on
production.
Luis
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