diff options
| author | Jerome Forissier <jerome.forissier@linaro.org> | 2017-03-08 08:29:41 +0100 |
|---|---|---|
| committer | Jérôme Forissier <jerome.forissier@linaro.org> | 2017-05-30 09:51:51 +0200 |
| commit | 236601217f7ecfb4a1511421299e77057cfdbde0 (patch) | |
| tree | 4bbb7cc9a5890821703026829026413870419491 /core/kernel | |
| parent | da033e69c2ce073850c57f5f9ec175e2f40c6f0a (diff) | |
core: remove __early_bss
Initialize the .bss section early from assembler before entering C
code. As a result, the __early_bss qualifier is not needed anymore.
Remove it, as well as the related symbols (__early_bss_start and
__early_bss_end).
This makes the code simpler hence easier to maintain, at the expense
of initialization time, since .bss is cleared before CPU caches are
turned on (and doing it later would mean some C function have been
called already). Here are some performance numbers measured on HiKey.
The "memset" column measures the time it takes to clear .bss in C,
without this patch. The "assembly" column reports the time taken by the
clear_bss loop in this patch. Timings were performed using CNTPCT.
Worst case is a ~1 ms overhead in boot time.
memset(): | assembly:
ms (bytes) | ms (bytes)
--------------+--------------
Aarch64 0.30 (72824) | 0.08 (73528)
Aarch32 0.27 (65016) | 1.24 (65408)
Aarch32/pager 0.03 (11328) | 0.23 (11736)
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (QEMU)
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (HiKey 32/64)
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (HiKey/pager)
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Diffstat (limited to 'core/kernel')
| -rw-r--r-- | core/kernel/console.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/core/kernel/console.c b/core/kernel/console.c index ebd13b56..36eb38b3 100644 --- a/core/kernel/console.c +++ b/core/kernel/console.c @@ -37,7 +37,7 @@ #include <libfdt.h> #endif -static struct serial_chip *serial_console __early_bss; +static struct serial_chip *serial_console; void __weak console_putc(int ch) { |