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Diffstat (limited to 'Documentation/cgroups/memcg_test.txt')
| -rw-r--r-- | Documentation/cgroups/memcg_test.txt | 72 |
1 files changed, 64 insertions, 8 deletions
diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt index 523a9c16c40..80ac454704b 100644 --- a/Documentation/cgroups/memcg_test.txt +++ b/Documentation/cgroups/memcg_test.txt @@ -1,6 +1,6 @@ Memory Resource Controller(Memcg) Implementation Memo. -Last Updated: 2009/1/19 -Base Kernel Version: based on 2.6.29-rc2. +Last Updated: 2010/2 +Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34). Because VM is getting complex (one of reasons is memcg...), memcg's behavior is complex. This is a document for memcg's internal behavior. @@ -24,7 +24,7 @@ Please note that implementation details can be changed. a page/swp_entry may be charged (usage += PAGE_SIZE) at - mem_cgroup_newpage_charge() + mem_cgroup_charge_anon() Called at new page fault and Copy-On-Write. mem_cgroup_try_charge_swapin() @@ -32,7 +32,7 @@ Please note that implementation details can be changed. Followed by charge-commit-cancel protocol. (With swap accounting) At commit, a charge recorded in swap_cgroup is removed. - mem_cgroup_cache_charge() + mem_cgroup_charge_file() Called at add_to_page_cache() mem_cgroup_cache_charge_swapin() @@ -244,7 +244,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. we have to check if OLDPAGE/NEWPAGE is a valid page after commit(). 8. LRU - Each memcg has its own private LRU. Now, it's handling is under global + Each memcg has its own private LRU. Now, its handling is under global VM's control (means that it's handled under global zone->lru_lock). Almost all routines around memcg's LRU is called by global LRU's list management functions under zone->lru_lock(). @@ -337,7 +337,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. race and lock dependency with other cgroup subsystems. example) - # mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices + # mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices and do task move, mkdir, rmdir etc...under this. @@ -348,7 +348,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. For example, test like following is good. (Shell-A) - # mount -t cgroup none /cgroup -t memory + # mount -t cgroup none /cgroup -o memory # mkdir /cgroup/test # echo 40M > /cgroup/test/memory.limit_in_bytes # echo 0 > /cgroup/test/tasks @@ -356,7 +356,63 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. (Shell-B) # move all tasks in /cgroup/test to /cgroup # /sbin/swapoff -a - # rmdir /test/cgroup + # rmdir /cgroup/test # kill malloc task. Of course, tmpfs v.s. swapoff test should be tested, too. + + 9.8 OOM-Killer + Out-of-memory caused by memcg's limit will kill tasks under + the memcg. When hierarchy is used, a task under hierarchy + will be killed by the kernel. + In this case, panic_on_oom shouldn't be invoked and tasks + in other groups shouldn't be killed. + + It's not difficult to cause OOM under memcg as following. + Case A) when you can swapoff + #swapoff -a + #echo 50M > /memory.limit_in_bytes + run 51M of malloc + + Case B) when you use mem+swap limitation. + #echo 50M > memory.limit_in_bytes + #echo 50M > memory.memsw.limit_in_bytes + run 51M of malloc + + 9.9 Move charges at task migration + Charges associated with a task can be moved along with task migration. + + (Shell-A) + #mkdir /cgroup/A + #echo $$ >/cgroup/A/tasks + run some programs which uses some amount of memory in /cgroup/A. + + (Shell-B) + #mkdir /cgroup/B + #echo 1 >/cgroup/B/memory.move_charge_at_immigrate + #echo "pid of the program running in group A" >/cgroup/B/tasks + + You can see charges have been moved by reading *.usage_in_bytes or + memory.stat of both A and B. + See 8.2 of Documentation/cgroups/memory.txt to see what value should be + written to move_charge_at_immigrate. + + 9.10 Memory thresholds + Memory controller implements memory thresholds using cgroups notification + API. You can use tools/cgroup/cgroup_event_listener.c to test it. + + (Shell-A) Create cgroup and run event listener + # mkdir /cgroup/A + # ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M + + (Shell-B) Add task to cgroup and try to allocate and free memory + # echo $$ >/cgroup/A/tasks + # a="$(dd if=/dev/zero bs=1M count=10)" + # a= + + You will see message from cgroup_event_listener every time you cross + the thresholds. + + Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds. + + It's good idea to test root cgroup as well. |