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@xxxxxxxxxxxx>
---
include/linux/raid/pq.h | 3 +++
lib/Kconfig | 8 ++++++++
lib/raid6/algos.c | 5 +++++
3 files changed, 16 insertions(+)
diff --git a/include/linux/raid/pq.h b/include/linux/raid/pq.h
index ea8505204fdf..faf7a4529a5a 100644
--- a/include/linux/raid/pq.h
+++ b/include/linux/raid/pq.h
@@ -67,6 +67,9 @@ 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 */
diff --git a/lib/Kconfig b/lib/Kconfig
index a9965f4af4dd..fcb05305a5a2 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -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
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index a753ff56670f..7e4f7a8ffa8e 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -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();
--
2.19.1.930.g4563a0d9d0-goog
