sched/fair: Fix comments (3841cdc3) · Commits · 戴 / test

Historically our periods (or p) argument in PELT denoted the number of full periods (what is now d2). However recent patches have changed this to the total decay (previously p+1), leading to a confusing discrepancy between comments and code. Try and clarify things by making periods (in code) and p (in comments) be the same thing (again). Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -2777,18 +2777,18 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
		u32 c1, c2, c3 = d3; /* y^0 == 1 */

		/*
		* c1 = d1 y^(p+1)
		* c1 = d1 y^p
		*/
		c1 = decay_load((u64)d1, periods);

		/*
		* p
		* p-1
		* c2 = 1024 \Sum y^n
		* n=1
		*
		* inf inf
		* = 1024 ( \Sum y^n - \Sum y^n - y^0 )
		* n=0 n=p+1
		* n=0 n=p
		*/
		c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;

		@@ -2808,14 +2808,14 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
		* \|<->\|<----------------->\|<--->\|
		* ... \|---x---\|------\| ... \|------\|-----x (now)
		*
		* p
		* u' = (u + d1) y^(p+1) + 1024 \Sum y^n + d3 y^0
		* p-1
		* u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
		* n=1
		*
		* = u y^(p+1) + (Step 1)
		* = u y^p + (Step 1)
		*
		* p
		* d1 y^(p+1) + 1024 \Sum y^n + d3 y^0 (Step 2)
		* p-1
		* d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2)
		* n=1
		*/
		static __always_inline u32

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