这里的目标是在 Linux 中内存压力期间将每个正在运行的进程的可执行代码保留在内存中。
在 Linux 中,我能够立即(1 秒)造成高内存压力并通过以下方式触发 OOM-killer:stress --vm-bytes $(awk '/MemAvailable/{printf "%d\n", $2 + 4000;}' < /proc/meminfo)k --vm-keep -m 4 --timeout 10s
(代码来自here)
Qubes OS R4.0 Fedora 28 AppVM 内具有 24000MB 最大 RAM。EDIT4:也许相关,但我忘记提及的是,我没有启用交换(即。CONFIG_SWAP
未设置)
dmesg 报告:
[ 867.746593] Mem-Info:
[ 867.746607] active_anon:1390927 inactive_anon:4670 isolated_anon:0
active_file:94 inactive_file:72 isolated_file:0
unevictable:13868 dirty:0 writeback:0 unstable:0
slab_reclaimable:5906 slab_unreclaimable:12919
mapped:1335 shmem:4805 pagetables:5126 bounce:0
free:40680 free_pcp:978 free_cma:0
有趣的部分是active_file:94 inactive_file:72
它们以千字节为单位,并且非常低。
这里的问题是,在内存压力期间,从磁盘重新读取可执行代码会导致磁盘抖动,从而导致冻结操作系统。 (但在上面的情况下,它只发生不到1秒)
我在内核中看到一段有趣的代码mm/vmscan.c:
if (page_referenced(page, 0, sc->target_mem_cgroup,
&vm_flags)) {
nr_rotated += hpage_nr_pages(page);
/*
* Identify referenced, file-backed active pages and
* give them one more trip around the active list. So
* that executable code get better chances to stay in
* memory under moderate memory pressure. Anon pages
* are not likely to be evicted by use-once streaming
* IO, plus JVM can create lots of anon VM_EXEC pages,
* so we ignore them here.
*/
if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
list_add(&page->lru, &l_active);
continue;
}
}
我认为如果有人可以指出如何改变这一点,而不是give them one more trip around the active list
我们得到它give them infinite trips around the active list
,那么工作应该完成。或者也许还有其他方法?
我可以修补和测试自定义内核。我只是不知道如何更改代码以便始终将活动的可执行代码保留在内存中(我相信这实际上可以避免磁盘抖动)。
EDIT:这是我到目前为止所做的工作(应用于内核 4.18.5):
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 32699b2..7636498 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -208,7 +208,7 @@ enum lru_list {
#define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)
-#define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
+#define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_INACTIVE_FILE; lru++)
static inline int is_file_lru(enum lru_list lru)
{
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 03822f8..1f3ffb5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2234,7 +2234,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
anon = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) +
lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES);
- file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
+ file = //lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES);
spin_lock_irq(&pgdat->lru_lock);
@@ -2345,7 +2345,7 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
sc->priority == DEF_PRIORITY);
blk_start_plug(&plug);
- while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
+ while (nr[LRU_INACTIVE_ANON] || //nr[LRU_ACTIVE_FILE] ||
nr[LRU_INACTIVE_FILE]) {
unsigned long nr_anon, nr_file, percentage;
unsigned long nr_scanned;
@@ -2372,7 +2372,8 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
* stop reclaiming one LRU and reduce the amount scanning
* proportional to the original scan target.
*/
- nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
+ nr_file = nr[LRU_INACTIVE_FILE] //+ nr[LRU_ACTIVE_FILE]
+ ;
nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
/*
@@ -2391,7 +2392,8 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
percentage = nr_anon * 100 / scan_target;
} else {
unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
- targets[LRU_ACTIVE_FILE] + 1;
+ //targets[LRU_ACTIVE_FILE] +
+ 1;
lru = LRU_FILE;
percentage = nr_file * 100 / scan_target;
}
还看过here在 github 上,因为在上面的代码中,制表符被转换为空格! (mirror1, mirror2)
我已经测试了上面的补丁(现在在 4000MB 最大 RAM 上,是的,比以前少了 20G!),即使使用已知会使操作系统磁盘永久冻结的 Firefox 编译,也不会再发生这种情况(oom-killer 是几乎立即杀死有问题的进程),也与上述stress
命令现在产生:
[ 745.830511] Mem-Info:
[ 745.830521] active_anon:855546 inactive_anon:20453 isolated_anon:0
active_file:26925 inactive_file:76 isolated_file:0
unevictable:10652 dirty:0 writeback:0 unstable:0
slab_reclaimable:26975 slab_unreclaimable:13525
mapped:24238 shmem:20456 pagetables:4028 bounce:0
free:14935 free_pcp:177 free_cma:0
That's active_file:26925 inactive_file:76
, 近 27 兆的活动文件...
所以,我不知道这有多好。我是否将所有活动文件而不只是可执行文件保留在内存中?在 Firefox 编译过程中,我有大约 500megActive(file)
(EDIT2:但这是根据:cat /proc/meminfo|grep -F -- 'Active(file)'
显示与上面不同的值active_file:
来自 dmesg!!!) 这让我怀疑这只是 exes/libs...
也许有人可以建议如何仅保留可执行代码?(如果这不是已经发生的情况)
想法?
EDIT3:使用上面的补丁,似乎可能有必要(定期?)运行sudo sysctl vm.drop_caches=1
释放一些陈旧的内存(?),这样如果我打电话stress
Firefox 编译后我得到:active_file:142281 inactive_file:0 isolated_file:0
(142megs)然后删除文件缓存(另一种方式:echo 1|sudo tee /proc/sys/vm/drop_caches
)然后运行stress
再次,我得到:active_file:22233 inactive_file:160 isolated_file:0
(22megs) - 我不确定......
没有上述补丁的结果:here
使用上述补丁的结果:here