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05 April 2024, 19:05:47 UTC
Revision 9282012fc0aa248b77a69f5eb802b67c5a16bb13 authored by Jaewon Kim on 25 July 2022, 09:52:12 UTC, committed by Andrew Morton on 29 July 2022, 18:33:37 UTC 
page_alloc: fix invalid watermark check on a negative value
 
There was a report that a task is waiting at the
throttle_direct_reclaim. The pgscan_direct_throttle in vmstat was
increasing.

This is a bug where zone_watermark_fast returns true even when the free
is very low. The commit f27ce0e14088 ("page_alloc: consider highatomic
reserve in watermark fast") changed the watermark fast to consider
highatomic reserve. But it did not handle a negative value case which
can be happened when reserved_highatomic pageblock is bigger than the
actual free.

If watermark is considered as ok for the negative value, allocating
contexts for order-0 will consume all free pages without direct reclaim,
and finally free page may become depleted except highatomic free.

Then allocating contexts may fall into throttle_direct_reclaim. This
symptom may easily happen in a system where wmark min is low and other
reclaimers like kswapd does not make free pages quickly.

Handle the negative case by using MIN.

Link: https://lkml.kernel.org/r/20220725095212.25388-1-jaewon31.kim@samsung.com
Fixes: f27ce0e14088 ("page_alloc: consider highatomic reserve in watermark fast")
Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Reported-by: GyeongHwan Hong <gh21.hong@samsung.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yong-Taek Lee <ytk.lee@samsung.com>
Cc: <stable@vger.kerenl.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1 parent 1f7ea54
Raw File
Tip revision: 9282012fc0aa248b77a69f5eb802b67c5a16bb13 authored by Jaewon Kim on 25 July 2022, 09:52:12 UTC
page_alloc: fix invalid watermark check on a negative value
Tip revision: 9282012
gen_autoksyms.sh 
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-only

# Create an autoksyms.h header file from the list of all module's needed symbols
# as recorded in *.usyms files and the user-provided symbol whitelist.

set -e

# Use "make V=1" to debug this script.
case "$KBUILD_VERBOSE" in
*1*)
	set -x
	;;
esac

read_modorder=

if [ "$1" = --modorder ]; then
	shift
	read_modorder=1
fi

output_file="$1"

needed_symbols=

# Special case for modversions (see modpost.c)
if grep -q "^CONFIG_MODVERSIONS=y$" include/config/auto.conf; then
	needed_symbols="$needed_symbols module_layout"
fi

ksym_wl=$(sed -n 's/^CONFIG_UNUSED_KSYMS_WHITELIST=\(.*\)$/\1/p' include/config/auto.conf)
if [ -n "$ksym_wl" ]; then
	[ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl"
	if [ ! -f "$ksym_wl" ] || [ ! -r "$ksym_wl" ]; then
		echo "ERROR: '$ksym_wl' whitelist file not found" >&2
		exit 1
	fi
fi

# Generate a new ksym list file with symbols needed by the current
# set of modules.
cat > "$output_file" << EOT
/*
 * Automatically generated file; DO NOT EDIT.
 */

EOT

{
	[ -n "${read_modorder}" ] && sed 's/ko$/usyms/' modules.order | xargs cat
	echo "$needed_symbols"
	[ -n "$ksym_wl" ] && cat "$ksym_wl"
} | sed -e 's/ /\n/g' | sed -n -e '/^$/!p' |
# Remove the dot prefix for ppc64; symbol names with a dot (.) hold entry
# point addresses.
sed -e 's/^\.//' |
sort -u |
# Ignore __this_module. It's not an exported symbol, and will be resolved
# when the final .ko's are linked.
grep -v '^__this_module$' |
sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$output_file"
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