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oom: make swap a soft requirement

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This commit is contained in:
Anita Zhang 2021-01-23 22:10:42 -08:00
parent c20aa7b171
commit 408a3bbd76
4 changed files with 21 additions and 8 deletions
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4
man/systemd-oomd.service.xml
View file

@ -56,8 +56,8 @@
<para>You will need a kernel compiled with PSI support. This is available in Linux 4.20 and above.</para>
<para>The system must also have swap enabled for <command>systemd-oomd</command> to function correctly. With swap
enabled, the system spends enough time swapping pages to let <command>systemd-oomd</command> react.
<para>It is highly recommended for the system to have swap enabled for <command>systemd-oomd</command> to function
optimally. With swap enabled, the system spends enough time swapping pages to let <command>systemd-oomd</command> react.
Without swap, the system enters a livelocked state much more quickly and may prevent <command>systemd-oomd</command>
from responding in a reasonable amount of time. See
<ulink url="https://chrisdown.name/2018/01/02/in-defence-of-swap.html">"In defence of swap: common misconceptions"</ulink>

8
src/oom/oomd-manager.c
View file

@ -6,6 +6,7 @@
#include "cgroup-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "memory-util.h"
#include "oomd-manager-bus.h"
#include "oomd-manager.h"
#include "path-util.h"
@ -294,9 +295,12 @@ static int monitor_cgroup_contexts_handler(sd_event_source *s, uint64_t usec, vo
return log_error_errno(r, "Failed to update monitored memory pressure cgroup contexts");
r = oomd_system_context_acquire("/proc/swaps", &m->system_context);
/* If there aren't units depending on swap actions, the only error we exit on is ENOMEM */
if (r == -ENOMEM || (r < 0 && !hashmap_isempty(m->monitored_swap_cgroup_contexts)))
/* If there aren't units depending on swap actions, the only error we exit on is ENOMEM.
* Allow ENOENT in the event that swap is disabled on the system. */
if (r == -ENOMEM || (r < 0 && r != -ENOENT && !hashmap_isempty(m->monitored_swap_cgroup_contexts)))
return log_error_errno(r, "Failed to acquire system context");
else if (r == -ENOENT)
zero(m->system_context);
/* If we're still recovering from a kill, don't try to kill again yet */
if (m->post_action_delay_start > 0) {

6
src/oom/oomd.c
View file

@ -142,10 +142,8 @@ static int run(int argc, char *argv[]) {
return log_error_errno(r, "Failed to get SwapTotal from /proc/meminfo: %m");
r = safe_atollu(swap, &s);
if (r < 0)
return log_error_errno(r, "Failed to parse SwapTotal from /proc/meminfo: %s: %m", swap);
if (s == 0)
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Requires swap to operate");
if (r < 0 || s == 0)
log_warning("Swap is currently not detected; memory pressure usage will be degraded");
if (!is_pressure_supported())
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Pressure Stall Information (PSI) is not supported");

11
src/oom/test-oomd-util.c
View file

@ -159,6 +159,11 @@ static void test_oomd_system_context_acquire(void) {
assert_se(ctx.swap_total == 0);
assert_se(ctx.swap_used == 0);
assert_se(write_string_file(path, "Filename Type Size Used Priority", WRITE_STRING_FILE_CREATE) == 0);
assert_se(oomd_system_context_acquire(path, &ctx) == 0);
assert_se(ctx.swap_total == 0);
assert_se(ctx.swap_used == 0);
assert_se(write_string_file(path, "Filename Type Size Used Priority\n"
"/swapvol/swapfile file 18971644 0 -3\n"
"/dev/vda2 partition 1999868 993780 -2", WRITE_STRING_FILE_CREATE) == 0);
@ -268,6 +273,12 @@ static void test_oomd_swap_free_below(void) {
.swap_used = 3310136 * 1024U,
};
assert_se(oomd_swap_free_below(&ctx, 20) == false);
ctx = (OomdSystemContext) {
.swap_total = 0,
.swap_used = 0,
};
assert_se(oomd_swap_free_below(&ctx, 20) == false);
}
static void test_oomd_sort_cgroups(void) {