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e4779015fd
Patch series "mm/damon: Fix fake /proc/loadavg reports", v3. This patchset fixes DAMON's fake load report issue. The first patch makes yet another variant of usleep_range() for this fix, and the second patch fixes the issue of DAMON by making it using the newly introduced function. This patch (of 2): Some kernel threads such as DAMON could need to repeatedly sleep in micro seconds level. Because usleep_range() sleeps in uninterruptible state, however, such threads would make /proc/loadavg reports fake load. To help such cases, this commit implements a variant of usleep_range() called usleep_idle_range(). It is same to usleep_range() but sets the state of the current task as TASK_IDLE while sleeping. Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Cc: John Stultz <john.stultz@linaro.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
91 lines
2.4 KiB
C
91 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_DELAY_H
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#define _LINUX_DELAY_H
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/*
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* Copyright (C) 1993 Linus Torvalds
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*
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* Delay routines, using a pre-computed "loops_per_jiffy" value.
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*
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* Please note that ndelay(), udelay() and mdelay() may return early for
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* several reasons:
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* 1. computed loops_per_jiffy too low (due to the time taken to
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* execute the timer interrupt.)
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* 2. cache behaviour affecting the time it takes to execute the
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* loop function.
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* 3. CPU clock rate changes.
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*
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* Please see this thread:
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* https://lists.openwall.net/linux-kernel/2011/01/09/56
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*/
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#include <linux/math.h>
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#include <linux/sched.h>
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extern unsigned long loops_per_jiffy;
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#include <asm/delay.h>
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/*
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* Using udelay() for intervals greater than a few milliseconds can
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* risk overflow for high loops_per_jiffy (high bogomips) machines. The
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* mdelay() provides a wrapper to prevent this. For delays greater
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* than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture
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* specific values can be defined in asm-???/delay.h as an override.
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* The 2nd mdelay() definition ensures GCC will optimize away the
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* while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G.
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*/
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#ifndef MAX_UDELAY_MS
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#define MAX_UDELAY_MS 5
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#endif
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#ifndef mdelay
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#define mdelay(n) (\
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(__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
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({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
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#endif
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#ifndef ndelay
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static inline void ndelay(unsigned long x)
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{
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udelay(DIV_ROUND_UP(x, 1000));
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}
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#define ndelay(x) ndelay(x)
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#endif
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extern unsigned long lpj_fine;
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void calibrate_delay(void);
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void __attribute__((weak)) calibration_delay_done(void);
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void msleep(unsigned int msecs);
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unsigned long msleep_interruptible(unsigned int msecs);
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void usleep_range_state(unsigned long min, unsigned long max,
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unsigned int state);
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static inline void usleep_range(unsigned long min, unsigned long max)
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{
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usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
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}
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static inline void usleep_idle_range(unsigned long min, unsigned long max)
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{
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usleep_range_state(min, max, TASK_IDLE);
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}
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static inline void ssleep(unsigned int seconds)
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{
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msleep(seconds * 1000);
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}
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/* see Documentation/timers/timers-howto.rst for the thresholds */
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static inline void fsleep(unsigned long usecs)
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{
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if (usecs <= 10)
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udelay(usecs);
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else if (usecs <= 20000)
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usleep_range(usecs, 2 * usecs);
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else
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msleep(DIV_ROUND_UP(usecs, 1000));
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}
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#endif /* defined(_LINUX_DELAY_H) */
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