diff options
Diffstat (limited to 'init/Kconfig')
| -rw-r--r-- | init/Kconfig | 46 |
1 files changed, 42 insertions, 4 deletions
diff --git a/init/Kconfig b/init/Kconfig index 41066e49e880..a291b7ef4738 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -807,15 +807,53 @@ config LOG_BUF_SHIFT range 12 21 default 17 help - Select kernel log buffer size as a power of 2. + Select the minimal kernel log buffer size as a power of 2. + The final size is affected by LOG_CPU_MAX_BUF_SHIFT config + parameter, see below. Any higher size also might be forced + by "log_buf_len" boot parameter. + Examples: - 17 => 128 KB + 17 => 128 KB 16 => 64 KB - 15 => 32 KB - 14 => 16 KB + 15 => 32 KB + 14 => 16 KB 13 => 8 KB 12 => 4 KB +config LOG_CPU_MAX_BUF_SHIFT + int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" + range 0 21 + default 12 if !BASE_SMALL + default 0 if BASE_SMALL + help + This option allows to increase the default ring buffer size + according to the number of CPUs. The value defines the contribution + of each CPU as a power of 2. The used space is typically only few + lines however it might be much more when problems are reported, + e.g. backtraces. + + The increased size means that a new buffer has to be allocated and + the original static one is unused. It makes sense only on systems + with more CPUs. Therefore this value is used only when the sum of + contributions is greater than the half of the default kernel ring + buffer as defined by LOG_BUF_SHIFT. The default values are set + so that more than 64 CPUs are needed to trigger the allocation. + + Also this option is ignored when "log_buf_len" kernel parameter is + used as it forces an exact (power of two) size of the ring buffer. + + The number of possible CPUs is used for this computation ignoring + hotplugging making the compuation optimal for the the worst case + scenerio while allowing a simple algorithm to be used from bootup. + + Examples shift values and their meaning: + 17 => 128 KB for each CPU + 16 => 64 KB for each CPU + 15 => 32 KB for each CPU + 14 => 16 KB for each CPU + 13 => 8 KB for each CPU + 12 => 4 KB for each CPU + # # Architectures with an unreliable sched_clock() should select this: # |