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platform: limit the maximum size of sysctl cache

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When the logging level is DEBUG or TRACE, we keep all the sysctl
values we read in a cache to log how they change. Currently there is
no limit on the size of this cache and it can take a large amount of
memory.

Implement a LRU cache where the oldest entries are deleted to make
space for new ones.

https://github.com/NetworkManager/NetworkManager/pull/294
This commit is contained in:
Beniamino Galvani
2019-02-05 11:11:16 +01:00
parent fb1baa636b
commit 3a0f7114fe
1 changed files with 46 additions and 15 deletions
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61
src/platform/nm-linux-platform.c
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@@ -376,8 +376,8 @@ typedef struct {
bool pruning[_DELAYED_ACTION_IDX_REFRESH_ALL_NUM];
bool sysctl_get_warned;
GHashTable *sysctl_get_prev_values;
CList sysctl_list;
NMUdevClient *udev_client;
@@ -4156,41 +4156,72 @@ _nm_logging_clear_platform_logging_cache (void)
g_hash_table_destroy (priv->sysctl_get_prev_values);
priv->sysctl_get_prev_values = NULL;
priv->sysctl_get_warned = FALSE;
}
}
typedef struct {
const char *path;
CList lst;
char *value;
char path_data[];
} SysctlCacheEntry;
static void
sysctl_cache_entry_free (SysctlCacheEntry *entry)
{
c_list_unlink_stale (&entry->lst);
g_free (entry->value);
g_free (entry);
}
static void
_log_dbg_sysctl_get_impl (NMPlatform *platform, const char *pathid, const char *contents)
{
NMLinuxPlatformPrivate *priv = NM_LINUX_PLATFORM_GET_PRIVATE (platform);
const char *prev_value = NULL;
SysctlCacheEntry *entry = NULL;
if (!priv->sysctl_get_prev_values) {
sysctl_clear_cache_list = g_slist_prepend (sysctl_clear_cache_list, platform);
priv->sysctl_get_prev_values = g_hash_table_new_full (nm_str_hash, g_str_equal, g_free, g_free);
c_list_init (&priv->sysctl_list);
priv->sysctl_get_prev_values = g_hash_table_new_full (nm_pstr_hash,
nm_pstr_equal,
(GDestroyNotify) sysctl_cache_entry_free,
NULL);
} else
prev_value = g_hash_table_lookup (priv->sysctl_get_prev_values, pathid);
entry = g_hash_table_lookup (priv->sysctl_get_prev_values, &pathid);
if (prev_value) {
if (strcmp (prev_value, contents) != 0) {
if (entry) {
if (!nm_streq (entry->value, contents)) {
gs_free char *contents_escaped = g_strescape (contents, NULL);
gs_free char *prev_value_escaped = g_strescape (prev_value, NULL);
gs_free char *prev_value_escaped = g_strescape (entry->value, NULL);
_LOGD ("sysctl: reading '%s': '%s' (changed from '%s' on last read)", pathid, contents_escaped, prev_value_escaped);
g_hash_table_insert (priv->sysctl_get_prev_values, g_strdup (pathid), g_strdup (contents));
g_free (entry->value);
entry->value = g_strdup (contents);
}
c_list_unlink_stale (&entry->lst);
c_list_link_front (&priv->sysctl_list, &entry->lst);
} else {
gs_free char *contents_escaped = g_strescape (contents, NULL);
SysctlCacheEntry *old;
size_t len;
len = strlen (pathid);
entry = g_malloc (sizeof (SysctlCacheEntry) + len + 1);
entry->value = g_strdup (contents);
entry->path = entry->path_data;
memcpy (entry->path_data, pathid, len + 1);
/* Remove oldest entry when the cache becomes too big */
if (g_hash_table_size (priv->sysctl_get_prev_values) > 1000) {
old = c_list_last_entry (&priv->sysctl_list, SysctlCacheEntry, lst);
g_hash_table_remove (priv->sysctl_get_prev_values, old);
}
_LOGD ("sysctl: reading '%s': '%s'", pathid, contents_escaped);
g_hash_table_insert (priv->sysctl_get_prev_values, g_strdup (pathid), g_strdup (contents));
if ( !priv->sysctl_get_warned
&& g_hash_table_size (priv->sysctl_get_prev_values) > 50000) {
_LOGW ("sysctl: the internal cache for debug-logging of sysctl values grew pretty large. You can clear it by disabling debug-logging: `nmcli general logging level KEEP domains PLATFORM:INFO`.");
priv->sysctl_get_warned = TRUE;
}
g_hash_table_add (priv->sysctl_get_prev_values, entry);
c_list_link_front (&priv->sysctl_list, &entry->lst);
}
}