On 2020-10-14, Geert Uytterhoeven <ge...@linux-m68k.org> wrote: >> - Fully lockless ringbuffer implementation, including the support for >> continuous lines. It will allow to store and read messages in any >> situation wihtout the risk of deadlocks and without the need >> of temporary per-CPU buffers. > > linux-m68k-atari_defconfig$ bloat-o-meter vmlinux.old > vmlinux.lockless_ringbuffer > add/remove: 39/16 grow/shrink: 9/15 up/down: 214075/-4362 (209713) > Function old new delta > _printk_rb_static_infos - 180224 +180224 > _printk_rb_static_descs - 24576 +24576
131072 of _printk_rb_static_infos is reserved for dictionary usage. The rest (49152) is for the record meta data. Previously any dictionary usage and record meta data was embedded in the message buffer (log_buf, 65536). Since the meta data is now separate, setting CONFIG_LOG_BUF_SHIFT=15 would provide roughly the same amount of record storage as CONFIG_LOG_BUF_SHIFT=16 did with vmlinux.old. Then there would be: 32768: message buffer 24576: meta data 65536: dictionary data 12288: descriptor data Excluding the dictionary data, the total is 65536. (With vmlinux.old there is 65536 total with CONFIG_LOG_BUF_SHIFT=16.) It is the reserved dictionary data that is hurting us here. Should we provide a config option to kill the dictionary data? Should CONFIG_LOG_BUF_SHIFT do an implicit -1 so that the sizes (without dictionary data) are about the same as before? Maybe dictionaries should only exist in the dynamically allocated ringbuffer? John Ogness
