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lib/raid6: add option to skip algo benchmarking

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This is helpful for systems where fast startup time is important.
It is especially nice to avoid benchmarking RAID functions that are
never used (for example, BTRFS selects RAID6_PQ even if the parity RAID
mode is not in use).

This saves 250+ milliseconds of boot time on modern x86 and ARM systems
with a dozen or more available implementations.

The new option is defaulted to 'y' to match the previous behavior of
always benchmarking on init.

Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
Daniel Verkamp 2018-11-12 15:26:52 -08:00 committed by Shaohua Li
parent 0437de4fa0
commit be85f93ae2
3 changed files with 16 additions and 0 deletions
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3
include/linux/raid/pq.h
View File

@ -70,6 +70,9 @@ extern const char raid6_empty_zero_page[PAGE_SIZE];
#define MODULE_DESCRIPTION(desc)
#define subsys_initcall(x)
#define module_exit(x)
#define IS_ENABLED(x) (x)
#define CONFIG_RAID6_PQ_BENCHMARK 1
#endif /* __KERNEL__ */
/* Routine choices */

8
lib/Kconfig
View File

@ -10,6 +10,14 @@ menu "Library routines"
config RAID6_PQ
tristate
config RAID6_PQ_BENCHMARK
bool "Automatically choose fastest RAID6 PQ functions"
depends on RAID6_PQ
default y
help
Benchmark all available RAID6 PQ functions on init and choose the
fastest one.
config BITREVERSE
tristate

5
lib/raid6/algos.c
View File

@ -163,6 +163,11 @@ static inline const struct raid6_calls *raid6_choose_gen(
if ((*algo)->valid && !(*algo)->valid())
continue;
if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
best = *algo;
break;
}
perf = 0;
preempt_disable();