Messages in this thread | | | Subject | Re: [GIT PULL] printk for 5.10 (includes lockless ringbuffer) | From | Rasmus Villemoes <> | Date | Wed, 14 Oct 2020 16:58:27 +0200 |
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On 14/10/2020 16.16, Geert Uytterhoeven wrote: > Hi Petr, > > On Mon, Oct 12, 2020 at 4:50 PM Petr Mladek <pmladek@suse.com> 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 > [...] > > Seriously?!? Or am I being misled by the tools? > > linux-m68k-atari_defconfig$ size vmlinux.old vmlinux.lockless_ringbuffer > text data bss dec hex filename > 3559108 941716 177772 4678596 4763c4 vmlinux.old > 3563922 1152496 175276 4891694 4aa42e vmlinux.lockless_ringbuffer > > Apparently not...
Hm, that's quite a lot. And the only reason the buffers don't live entirely in .bss is because a few of their entries have non-zero initializers.
Perhaps one could add a .init.text.initialize_static_data section of function pointers, with the _DEFINE_PRINTKRB macro growing something like
static void __init __initialize_printkrb_##name(void) { \ _##name##_descs[_DESCS_COUNT(descbits) - 1] = ...; \ _##name##_infos[0] = ...; \ _##name##_infos[_DESCS_COUNT(descbits) - 1] = ...; \ } \ static_data_initializer(__initialize_printkrb_##name);
with static_data_initalizer being the obvious yoga for putting a function pointer in the .init.text.initialize_static_data section. Then very early in start_kernel(), probably first thing, iterate that section and call all the functions. But maybe that's not even early enough?
Rasmus
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