Commit 9476db97 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

mm: memcontrol: simplify move precharge function

The move precharge function does some baroque things: it tries raw
res_counter charging of the entire amount first, and then falls back to
a loop of one-by-one charges, with checks for pending signals and
cond_resched() batching.

Just use mem_cgroup_try_charge() without __GFP_WAIT for the first bulk
charge attempt.  In the one-by-one loop, remove the signal check (this
is already checked in try_charge), and simply call cond_resched() after
every charge - it's not that expensive.
Signed-off-by: default avatarJohannes Weiner <>
Acked-by: default avatarMichal Hocko <>
Cc: Hugh Dickins <>
Cc: Tejun Heo <>
Cc: Vladimir Davydov <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0029e19e
......@@ -6385,56 +6385,38 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
/* Handlers for move charge at task migration. */
static int mem_cgroup_do_precharge(unsigned long count)
int ret = 0;
int batch_count = PRECHARGE_COUNT_AT_ONCE;
struct mem_cgroup *memcg =;
if (mem_cgroup_is_root(memcg)) {
if (mem_cgroup_is_root( {
mc.precharge += count;
/* we don't need css_get for root */
return ret;
/* try to charge at once */
if (count > 1) {
struct res_counter *dummy;
* "memcg" cannot be under rmdir() because we've already checked
* by cgroup_lock_live_cgroup() that it is not removed and we
* are still under the same cgroup_mutex. So we can postpone
* css_get().
if (res_counter_charge(&memcg->res, PAGE_SIZE * count, &dummy))
goto one_by_one;
if (do_swap_account && res_counter_charge(&memcg->memsw,
PAGE_SIZE * count, &dummy)) {
res_counter_uncharge(&memcg->res, PAGE_SIZE * count);
goto one_by_one;
/* Try a single bulk charge without reclaim first */
ret = mem_cgroup_try_charge(, GFP_KERNEL & ~__GFP_WAIT, count);
if (!ret) {
mc.precharge += count;
return ret;
/* fall back to one by one charge */
/* Try charges one by one with reclaim */
while (count--) {
if (signal_pending(current)) {
ret = -EINTR;
if (!batch_count--) {
ret = mem_cgroup_try_charge(memcg,
ret = mem_cgroup_try_charge(,
* In case of failure, any residual charges against
* will be dropped by mem_cgroup_clear_mc()
* later on.
if (ret)
/* mem_cgroup_clear_mc() will do uncharge later */
return ret;
return ret;
return 0;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment