lib/raid6: add option to skip algo benchmarking (be85f93a) · Commits · 戴 / test

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>

include/linux/raid/pq.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -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 */

lib/Kconfig

+8 −0

Original line number	Diff line number	Diff line
		@@ -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

lib/raid6/algos.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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();

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