Messages in this thread | | | Date | Wed, 6 Jun 2012 09:33:22 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] printk: Shrink printk_sched buffer size, eliminate it when !CONFIG_PRINTK |
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* Joe Perches <joe@perches.com> wrote:
> The size of the per-cpu printk_sched buf is much larger > than necessary. The maximum sched message emitted is > ~80 bytes. Shrink the allocation for this printk_sched > buffer from 512 bytes to 128. > > printk_sched creates an unnecessary per-cpu buffer when > CONFIG_PRINTK is not enabled. Remove it when appropriate > so embedded uses save a bit of space too. > > Signed-off-by: Joe Perches <joe@perches.com> > --- > kernel/printk.c | 14 ++++++++++---- > 1 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/kernel/printk.c b/kernel/printk.c > index 32462d2..61cff0b 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -1726,24 +1726,30 @@ int is_console_locked(void) > } > > /* > - * Delayed printk version, for scheduler-internal messages: > + * Delayed printk version, for scheduler-internal messages. > + * Not the normal 512 as it's a bit wasteful, sched messages are short, > + * and 128 is more than sufficient for all current messages. > */ > -#define PRINTK_BUF_SIZE 512 > +#define PRINTK_SCHED_BUF_SIZE 128 > > #define PRINTK_PENDING_WAKEUP 0x01 > #define PRINTK_PENDING_SCHED 0x02 > > static DEFINE_PER_CPU(int, printk_pending); > -static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf); > +#ifdef CONFIG_PRINTK > +static DEFINE_PER_CPU(char [PRINTK_SCHED_BUF_SIZE], printk_sched_buf); > +#endif > > void printk_tick(void) > { > if (__this_cpu_read(printk_pending)) { > int pending = __this_cpu_xchg(printk_pending, 0); > +#ifdef CONFIG_PRINTK > if (pending & PRINTK_PENDING_SCHED) { > char *buf = __get_cpu_var(printk_sched_buf); > printk(KERN_WARNING "[sched_delayed] %s", buf); > } > +#endif > if (pending & PRINTK_PENDING_WAKEUP) > wake_up_interruptible(&log_wait); > } > @@ -2189,7 +2195,7 @@ int printk_sched(const char *fmt, ...) > buf = __get_cpu_var(printk_sched_buf); > > va_start(args, fmt); > - r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args); > + r = vsnprintf(buf, PRINTK_SCHED_BUF_SIZE, fmt, args); > va_end(args); > > __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
The change makes sense but the further proliferation of #ifdefs is rather ugly and shows confusion: fundamentally, if we are going to cut out more printk functionality in the !CONFIG_PRINTK we might as well disable the whole thing, not just the printk_sched bits.
Thanks,
Ingo
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