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    Subject[RFC][PATCH 2/9] soft limit framework for memcg.
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    Add minimal modification for soft limit to res_counter_charge() and memcontol.c
    Based on Balbir Singh <balbir@linux.vnet.ibm.com> 's work but most of
    features are removed. (dropped or moved to later patch.)

    This is for building a frame to implement soft limit handler in memcg.
    - Checks soft limit status at every charge.
    - Adds mem_cgroup_soft_limit_check() as a function to detect we need
    check now or not.
    - mem_cgroup_update_soft_limit() is a function for updates internal status
    of soft limit controller of memcg.
    - As an experimental, this has no hooks in uncharge path.

    Changelog: v1 -> v2
    - removed "update" from mem_cgroup_free() (revisit in later patch.)

    Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    ---
    include/linux/res_counter.h | 3 ++-
    kernel/res_counter.c | 12 +++++++++++-
    mm/memcontrol.c | 19 +++++++++++++++++--
    3 files changed, 30 insertions(+), 4 deletions(-)

    Index: softlimit-test2/include/linux/res_counter.h
    ===================================================================
    --- softlimit-test2.orig/include/linux/res_counter.h
    +++ softlimit-test2/include/linux/res_counter.h
    @@ -112,7 +112,8 @@ void res_counter_init(struct res_counter
    int __must_check res_counter_charge_locked(struct res_counter *counter,
    unsigned long val);
    int __must_check res_counter_charge(struct res_counter *counter,
    - unsigned long val, struct res_counter **limit_fail_at);
    + unsigned long val, struct res_counter **limit_fail_at,
    + bool *soft_limit_failure);

    /*
    * uncharge - tell that some portion of the resource is released
    Index: softlimit-test2/kernel/res_counter.c
    ===================================================================
    --- softlimit-test2.orig/kernel/res_counter.c
    +++ softlimit-test2/kernel/res_counter.c
    @@ -37,9 +37,11 @@ int res_counter_charge_locked(struct res
    }

    int res_counter_charge(struct res_counter *counter, unsigned long val,
    - struct res_counter **limit_fail_at)
    + struct res_counter **limit_fail_at,
    + bool *soft_limit_failure)
    {
    int ret;
    + int soft_cnt = 0;
    unsigned long flags;
    struct res_counter *c, *u;

    @@ -48,6 +50,8 @@ int res_counter_charge(struct res_counte
    for (c = counter; c != NULL; c = c->parent) {
    spin_lock(&c->lock);
    ret = res_counter_charge_locked(c, val);
    + if (!res_counter_soft_limit_check_locked(c))
    + soft_cnt += 1;
    spin_unlock(&c->lock);
    if (ret < 0) {
    *limit_fail_at = c;
    @@ -55,6 +59,12 @@ int res_counter_charge(struct res_counte
    }
    }
    ret = 0;
    + if (soft_limit_failure) {
    + if (!soft_cnt)
    + *soft_limit_failure = false;
    + else
    + *soft_limit_failure = true;
    + }
    goto done;
    undo:
    for (u = counter; u != c; u = u->parent) {
    Index: softlimit-test2/mm/memcontrol.c
    ===================================================================
    --- softlimit-test2.orig/mm/memcontrol.c
    +++ softlimit-test2/mm/memcontrol.c
    @@ -897,6 +897,15 @@ static void record_last_oom(struct mem_c
    mem_cgroup_walk_tree(mem, NULL, record_last_oom_cb);
    }

    +static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
    +{
    + return false;
    +}
    +
    +static void mem_cgroup_update_soft_limit(struct mem_cgroup *mem)
    +{
    + return;
    +}

    /*
    * Unlike exported interface, "oom" parameter is added. if oom==true,
    @@ -909,6 +918,7 @@ static int __mem_cgroup_try_charge(struc
    struct mem_cgroup *mem, *mem_over_limit;
    int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
    struct res_counter *fail_res;
    + bool soft_fail;

    if (unlikely(test_thread_flag(TIF_MEMDIE))) {
    /* Don't account this! */
    @@ -938,12 +948,13 @@ static int __mem_cgroup_try_charge(struc
    int ret;
    bool noswap = false;

    - ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res);
    + ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res,
    + &soft_fail);
    if (likely(!ret)) {
    if (!do_swap_account)
    break;
    ret = res_counter_charge(&mem->memsw, PAGE_SIZE,
    - &fail_res);
    + &fail_res, NULL);
    if (likely(!ret))
    break;
    /* mem+swap counter fails */
    @@ -985,6 +996,10 @@ static int __mem_cgroup_try_charge(struc
    goto nomem;
    }
    }
    +
    + if (soft_fail && mem_cgroup_soft_limit_check(mem))
    + mem_cgroup_update_soft_limit(mem);
    +
    return 0;
    nomem:
    css_put(&mem->css);


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