85 lines
3.4 KiB
Bash
85 lines
3.4 KiB
Bash
#!/bin/sh
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# Transparent huge pages as the mesh sets them on this machine (module kernel, novox/hq issue 746).
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# Written by the mesh from this machine's setting transparent-huge-pages and run by
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# mesh-kernel-huge-pages.service: `apply` at boot and whenever the setting changes, `restore` when the
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# unit stops (the module unassigned, or the machine shutting down). Replaced on every push; change the
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# setting, never this file. A change of the setting reloads the unit, which runs `apply` again: the mode
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# moves straight to the new value and never passes back through the one the machine was found with.
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#
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# huge-pages apply|restore [<the kernel's transparent_hugepage directory> [<this module's state>]]
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#
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# The two directories are arguments only so the module's tests can run this against a stand-in tree.
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set -eu
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want='${config:transparent-huge-pages}'
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sys=/sys/kernel/mm/transparent_hugepage
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state='${dir:state}'
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[ $# -ge 2 ] && sys=$2
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[ $# -ge 3 ] && state=$3
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case "$want" in
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always | madvise | never) ;;
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*)
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echo "the setting transparent-huge-pages is '$want'; the kernel takes always, madvise or never" >&2
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exit 2
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;;
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esac
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[ -f "$sys/enabled" ] || {
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echo "this kernel has no $sys/enabled: it was built without transparent huge pages, so there is nothing to set" >&2
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exit 1
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}
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# The mode in force is the word the kernel brackets: "always [madvise] never". A file holding one bare
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# word (the stand-in tree of the tests) is read as that word.
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mode() { sed -n -e 's/.*\[\([a-z]*\)\].*/\1/p' -e t -e 's/^ *\([a-z]*\) *$/\1/p' "$sys/enabled"; }
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[ $# -ge 1 ] || set -- usage
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case "$1" in
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apply)
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now=$(mode)
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# What the machine had before the mesh first set it, kept once, so `restore` gives it back.
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[ -s "$state/found" ] || printf '%s\n' "$now" >"$state/found"
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if [ "$now" = "$want" ]; then
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echo "transparent huge pages: $want, as set"
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exit 0
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fi
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printf '%s\n' "$want" >"$sys/enabled"
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got=$(mode)
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[ "$got" = "$want" ] || {
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echo "wrote $want to $sys/enabled and the kernel says $got" >&2
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exit 1
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}
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echo "transparent huge pages: $now -> $want"
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# A file folio already in the page cache keeps its size: the active journal files, mapped by journald
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# and by every reader, stay in 2 MiB folios until they are archived (issue 746). Rotating starts new
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# files that are mapped under the new mode. A failed rotation is said and does not fail the setting.
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# At boot nothing is in huge folios yet, and the persistent journal opens only after this unit: no rotation
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# while the service manager is still bringing the machine up.
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booting=$(systemctl is-system-running 2>/dev/null || true)
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case "$booting" in
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initializing | starting) echo "the machine is still starting: nothing to rotate yet" ;;
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*)
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if [ "$want" != always ] && command -v journalctl >/dev/null 2>&1; then
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journalctl --rotate || echo "the journal could not be rotated: its active files keep their huge pages until they are archived" >&2
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fi
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;;
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esac
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;;
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restore)
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found=$(cat "$state/found" 2>/dev/null || true)
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case "$found" in
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always | madvise | never)
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printf '%s\n' "$found" >"$sys/enabled"
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echo "transparent huge pages: back to $found, as the machine had them"
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;;
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*) echo "transparent huge pages: nothing recorded as found, left at $(mode)" ;;
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esac
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# Unassigned or shut down: nothing of the module is kept; the next start records what it finds again.
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rm -f "$state/found"
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;;
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*)
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echo "usage: huge-pages apply|restore [<transparent_hugepage directory> [<state directory>]]" >&2
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exit 2
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;;
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esac
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