Re: [PATCH 5/5] printk: Allocate kernel log buffer earlier

Yinghai Lu
2011-02-17T23:21:41Z

On Thu, Feb 17, 2011 at 10:51 AM, Mike Travis <travis@sgi.com> wrote:
> On larger systems, because of the numerous ACPI, Bootmem and EFI
> messages, the static log buffer overflows before the larger one
> specified by the log_buf_len param is allocated.  Minimize the
> overflow by allocating the new log buffer as soon as possible.
>
> All arch's are covered by the "setup_log_buf" in start_kernel().
> The x86 arch allocates it right after bootmem is created.
>
> v1: Added pertinent __init & __initdata specifiers.
> v2: updated to apply to x86-tip
>
> Signed-off-by: Mike Travis <travis@sgi.com>
> Reviewed-by: Jack Steiner <steiner@sgi.com>
> Reviewed-by: Robin Holt <holt@sgi.com>
> ---
>  arch/x86/kernel/setup.c |    5 ++
>  include/linux/printk.h  |    4 ++
>  init/main.c             |    1
>  kernel/printk.c         |   81 +++++++++++++++++++++++++++++-------------------
>  4 files changed, 60 insertions(+), 31 deletions(-)
>
> --- linux.orig/arch/x86/kernel/setup.c
> +++ linux/arch/x86/kernel/setup.c
> @@ -1007,6 +1007,11 @@ void __init setup_arch(char **cmdline_p)
>        memblock_find_dma_reserve();
>        dma32_reserve_bootmem();
>
> +       /*
> +        * Allocate bigger log buffer as early as possible
> +        */
> +       setup_log_buf();
> +
>  #ifdef CONFIG_KVM_CLOCK
>        kvmclock_init();
>  #endif
> --- linux.orig/include/linux/printk.h
> +++ linux/include/linux/printk.h
> @@ -1,6 +1,8 @@
>  #ifndef __KERNEL_PRINTK__
>  #define __KERNEL_PRINTK__
>
> +#include <linux/init.h>
> +
>  extern const char linux_banner[];
>  extern const char linux_proc_banner[];
>
> @@ -89,6 +91,8 @@ int no_printk(const char *fmt, ...)
>  extern asmlinkage __attribute__ ((format (printf, 1, 2)))
>  void early_printk(const char *fmt, ...);
>
> +void __init setup_log_buf(void);
> +
>  extern int printk_needs_cpu(int cpu);
>  extern void printk_tick(void);
>
> --- linux.orig/init/main.c
> +++ linux/init/main.c
> @@ -592,6 +592,7 @@ asmlinkage void __init start_kernel(void
>         * These use large bootmem allocations and must precede
>         * kmem_cache_init()
>         */
> +       setup_log_buf();
>        pidhash_init();
>        vfs_caches_init_early();
>        sort_main_extable();
> --- linux.orig/kernel/printk.c
> +++ linux/kernel/printk.c
> @@ -162,46 +162,65 @@ void log_buf_kexec_setup(void)
>  }
>  #endif
>
> +static unsigned long __initdata new_log_buf_len;
>  static int __init log_buf_len_setup(char *str)
>  {
>        unsigned size = memparse(str, &str);
> -       unsigned long flags;
>
>        if (size)
>                size = roundup_pow_of_two(size);
> -       if (size > log_buf_len) {
> -               unsigned start, dest_idx, offset;
> -               char *new_log_buf;
> -
> -               new_log_buf = alloc_bootmem(size);
> -               if (!new_log_buf) {
> -                       printk(KERN_WARNING "log_buf_len: allocation failed\n");
> -                       goto out;
> -               }
> -
> -               spin_lock_irqsave(&logbuf_lock, flags);
> -               log_buf_len = size;
> -               log_buf = new_log_buf;
> -
> -               offset = start = min(con_start, log_start);
> -               dest_idx = 0;
> -               while (start != log_end) {
> -                       log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
> -                       start++;
> -                       dest_idx++;
> -               }
> -               log_start -= offset;
> -               con_start -= offset;
> -               log_end -= offset;
> -               spin_unlock_irqrestore(&logbuf_lock, flags);
> +       if (size > log_buf_len)
> +               new_log_buf_len = size;
>
> -               printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
> -       }
> -out:
> -       return 1;
> +       return 0;
>  }
> +early_param("log_buf_len", log_buf_len_setup);
>
> -__setup("log_buf_len=", log_buf_len_setup);
> +void __init setup_log_buf(void)
> +{
> +       unsigned long flags;
> +       unsigned start, dest_idx, offset;
> +       char *new_log_buf;
> +       char first_line[64], *first_nl;
> +
> +       if (!new_log_buf_len)
> +               return;
> +
> +       new_log_buf = alloc_bootmem(new_log_buf_len);
> +       memset(first_line, 0, sizeof(first_line));

use x86_memblock_find_range in x86 code?

you can do that much earlier before SRAT etc is parsed.

Thanks

Yinghai