20ea6adbf1
Build system: x86_64 Build-tested: bcm2708, bcm2709, bcm2710, bcm2711 Run-tested: bcm2708/RPiB+, bcm2709/RPi3B, bcm2710/RPi3B, bcm2711/RPi4B Signed-off-by: Marty Jones <mj8263788@gmail.com> Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
68 lines
2.5 KiB
Diff
68 lines
2.5 KiB
Diff
From 6896ae528e4654e6f4bdff575337237f40de48b2 Mon Sep 17 00:00:00 2001
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From: David Plowman <david.plowman@raspberrypi.com>
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Date: Tue, 29 Mar 2022 16:10:06 +0100
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Subject: [PATCH] mm,page_alloc,cma: introduce a customisable threshold
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for allocating pages in cma
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On some platforms the cma area can be half the entire system memory,
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meaning that allocations start happening in the cma area immediately.
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This leads to fragmentation and subsequent fatal cma_alloc failures.
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We introduce an "alloc_in_cma_threshold" parameter which requires that
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this many sixteenths of the free pages must be in cma before it will
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try to use them. By default this is set to 12, but the previous
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behaviour can be restored by setting it to 8 on startup.
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Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
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---
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mm/page_alloc.c | 28 +++++++++++++++++++++++++---
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1 file changed, 25 insertions(+), 3 deletions(-)
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--- a/mm/page_alloc.c
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+++ b/mm/page_alloc.c
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@@ -190,6 +190,27 @@ EXPORT_SYMBOL(init_on_alloc);
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DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
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EXPORT_SYMBOL(init_on_free);
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+#define ALLOC_IN_CMA_THRESHOLD_MAX 16
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+#define ALLOC_IN_CMA_THRESHOLD_DEFAULT 12
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+
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+static unsigned long _alloc_in_cma_threshold __read_mostly
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+ = ALLOC_IN_CMA_THRESHOLD_DEFAULT;
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+
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+static int __init alloc_in_cma_threshold_setup(char *buf)
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+{
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+ unsigned long res;
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+
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+ if (kstrtoul(buf, 10, &res) < 0 ||
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+ res > ALLOC_IN_CMA_THRESHOLD_MAX) {
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+ pr_err("Bad alloc_cma_threshold value\n");
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+ return 0;
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+ }
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+ _alloc_in_cma_threshold = res;
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+ pr_info("Setting alloc_in_cma_threshold to %lu\n", res);
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+ return 0;
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+}
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+early_param("alloc_in_cma_threshold", alloc_in_cma_threshold_setup);
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+
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static bool _init_on_alloc_enabled_early __read_mostly
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= IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);
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static int __init early_init_on_alloc(char *buf)
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@@ -2980,12 +3001,13 @@ __rmqueue(struct zone *zone, unsigned in
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if (IS_ENABLED(CONFIG_CMA)) {
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/*
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* Balance movable allocations between regular and CMA areas by
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- * allocating from CMA when over half of the zone's free memory
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- * is in the CMA area.
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+ * allocating from CMA when over more than a given proportion of
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+ * the zone's free memory is in the CMA area.
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*/
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if (alloc_flags & ALLOC_CMA &&
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zone_page_state(zone, NR_FREE_CMA_PAGES) >
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- zone_page_state(zone, NR_FREE_PAGES) / 2) {
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+ zone_page_state(zone, NR_FREE_PAGES) / ALLOC_IN_CMA_THRESHOLD_MAX
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+ * _alloc_in_cma_threshold) {
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page = __rmqueue_cma_fallback(zone, order);
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if (page)
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goto out;
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