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Revision 2bbd00aef0671bfe3c2ca5ba67097246257de125 authored by Johannes Weiner on 26 February 2021, 01:16:47 UTC, committed by Linus Torvalds on 26 February 2021, 17:41:00 UTC 
mm: vmstat: fix NOHZ wakeups for node stat changes
 
On NOHZ, the periodic vmstat flushers on each CPU can go to sleep and
won't wake up until stat changes are detected in the per-cpu deltas of the
zone vmstat counters.

In commit 75ef71840539 ("mm, vmstat: add infrastructure for per-node
vmstats") per-node counters were introduced, and subsequently most stats
were moved from the zone to the node level.  However, the node counters
weren't added to the NOHZ wakeup detection.

In theory this can cause per-cpu errors to remain in the user-reported
stats indefinitely.  In practice this only affects a handful of sub
counters (file_mapped, dirty and writeback e.g.) because other page state
changes at the node level likely involve a change at the zone level as
well (alloc and free, lru ops).  Also, nobody has complained.

Fix it up for completeness: wake up vmstat refreshing on node changes.
Also remove the BUILD_BUG_ONs that assert counter size; we haven't relied
on it since we added sizeof() to the range calculation in commit
13c9aaf7fa01 ("mm/vmstat.c: fix NUMA statistics updates").

Link: https://lkml.kernel.org/r/20210202184342.118513-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Raw File
cxl-base.h 
/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright 2014 IBM Corp.
 */

#ifndef _MISC_CXL_BASE_H
#define _MISC_CXL_BASE_H

#ifdef CONFIG_CXL_BASE

#define CXL_IRQ_RANGES 4

struct cxl_irq_ranges {
	irq_hw_number_t offset[CXL_IRQ_RANGES];
	irq_hw_number_t range[CXL_IRQ_RANGES];
};

extern atomic_t cxl_use_count;

static inline bool cxl_ctx_in_use(void)
{
       return (atomic_read(&cxl_use_count) != 0);
}

static inline void cxl_ctx_get(void)
{
       atomic_inc(&cxl_use_count);
}

static inline void cxl_ctx_put(void)
{
       atomic_dec(&cxl_use_count);
}

struct cxl_afu *cxl_afu_get(struct cxl_afu *afu);
void cxl_afu_put(struct cxl_afu *afu);
void cxl_slbia(struct mm_struct *mm);

#else /* CONFIG_CXL_BASE */

static inline bool cxl_ctx_in_use(void) { return false; }
static inline struct cxl_afu *cxl_afu_get(struct cxl_afu *afu) { return NULL; }
static inline void cxl_afu_put(struct cxl_afu *afu) {}
static inline void cxl_slbia(struct mm_struct *mm) {}

#endif /* CONFIG_CXL_BASE */

#endif
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