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core: optionally, accept a percentage value for MemoryLimit= and related settings

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If a percentage is used, it is taken relative to the installed RAM size. This
should make it easier to write generic unit files that adapt to the local system.
This commit is contained in:
Lennart Poettering 2016-06-08 19:36:09 +02:00
parent 9184ca48ea
commit 875ae5661a
2 changed files with 32 additions and 20 deletions
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36
man/systemd.resource-control.xml
View File

@ -228,9 +228,11 @@
reclaimed as long as memory can be reclaimed from unprotected units.</para>
<para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. This controls the
<literal>memory.low</literal> control group attribute. For details about this control group attribute, see
<ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
percentage value may be specified, which is taken relative to the installed physical memory on the
system. This controls the <literal>memory.low</literal> control group attribute. For details about this
control group attribute, see <ulink
url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>
<para>Implies <literal>MemoryAccounting=true</literal>.</para>
@ -247,7 +249,9 @@
aggressively in such cases. This is the main mechanism to control memory usage of a unit.</para>
<para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. If assigned the
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
percentage value may be specified, which is taken relative to the installed physical memory on the
system. If assigned the
special value <literal>infinity</literal>, no memory limit is applied. This controls the
<literal>memory.high</literal> control group attribute. For details about this control group attribute, see
<ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>
@ -268,8 +272,9 @@
last line of defense.</para>
<para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. If assigned the
special value <literal>infinity</literal>, no memory limit is applied. This controls the
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
percentage value may be specified, which is taken relative to the installed physical memory on the system. If
assigned the special value <literal>infinity</literal>, no memory limit is applied. This controls the
<literal>memory.max</literal> control group attribute. For details about this control group attribute, see
<ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>
@ -284,17 +289,14 @@
<term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term>
<listitem>
<para>Specify the limit on maximum memory usage of the
executed processes. The limit specifies how much process and
kernel memory can be used by tasks in this unit. Takes a
memory size in bytes. If the value is suffixed with K, M, G
or T, the specified memory size is parsed as Kilobytes,
Megabytes, Gigabytes, or Terabytes (with the base 1024),
respectively. If assigned the special value
<literal>infinity</literal>, no memory limit is applied. This
controls the <literal>memory.limit_in_bytes</literal>
control group attribute. For details about this control
group attribute, see <ulink
<para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is
taken relative to the installed physical memory on the system. If assigned the special value
<literal>infinity</literal>, no memory limit is applied. This controls the
<literal>memory.limit_in_bytes</literal> control group attribute. For details about this control group
attribute, see <ulink
url="https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt</ulink>.</para>
<para>Implies <literal>MemoryAccounting=true</literal>.</para>

16
src/core/load-fragment.c
View File

@ -2812,9 +2812,19 @@ int config_parse_memory_limit(
int r;
if (!isempty(rvalue) && !streq(rvalue, "infinity")) {
r = parse_size(rvalue, 1024, &bytes);
if (r < 0 || bytes < 1) {
log_syntax(unit, LOG_ERR, filename, line, r, "Memory limit '%s' invalid. Ignoring.", rvalue);
r = parse_percent(rvalue);
if (r < 0) {
r = parse_size(rvalue, 1024, &bytes);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Memory limit '%s' invalid. Ignoring.", rvalue);
return 0;
}
} else
bytes = (((physical_memory() / page_size()) * (uint64_t) r) / 100) * page_size();
if (bytes < 1) {
log_syntax(unit, LOG_ERR, filename, line, 0, "Memory limit '%s' too small. Ignoring.", rvalue);
return 0;
}
}