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: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -6385,56 +6385,38 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
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#ifdef CONFIG_MMU
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#ifdef CONFIG_MMU
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/* Handlers for move charge at task migration. */
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/* Handlers for move charge at task migration. */
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#define PRECHARGE_COUNT_AT_ONCE 256
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static int mem_cgroup_do_precharge(unsigned long count)
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static int mem_cgroup_do_precharge(unsigned long count)
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{
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{
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int ret = 0;
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int ret = 0;
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int batch_count = PRECHARGE_COUNT_AT_ONCE;
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struct mem_cgroup *memcg = mc.to;
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if (mem_cgroup_is_root(memcg)) {
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if (mem_cgroup_is_root(mc.to)) {
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mc.precharge += count;
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mc.precharge += count;
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/* we don't need css_get for root */
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/* we don't need css_get for root */
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return ret;
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return ret;
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}
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}
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/* try to charge at once */
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if (count > 1) {
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/* Try a single bulk charge without reclaim first */
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struct res_counter *dummy;
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ret = mem_cgroup_try_charge(mc.to, GFP_KERNEL & ~__GFP_WAIT, count);
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/*
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if (!ret) {
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* "memcg" cannot be under rmdir() because we've already checked
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* by cgroup_lock_live_cgroup() that it is not removed and we
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* are still under the same cgroup_mutex. So we can postpone
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* css_get().
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*/
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if (res_counter_charge(&memcg->res, PAGE_SIZE * count, &dummy))
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goto one_by_one;
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if (do_swap_account && res_counter_charge(&memcg->memsw,
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PAGE_SIZE * count, &dummy)) {
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res_counter_uncharge(&memcg->res, PAGE_SIZE * count);
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goto one_by_one;
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}
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mc.precharge += count;
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mc.precharge += count;
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return ret;
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return ret;
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}
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}
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one_by_one:
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/* fall back to one by one charge */
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/* Try charges one by one with reclaim */
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while (count--) {
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while (count--) {
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if (signal_pending(current)) {
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ret = mem_cgroup_try_charge(mc.to,
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ret = -EINTR;
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break;
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}
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if (!batch_count--) {
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batch_count = PRECHARGE_COUNT_AT_ONCE;
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cond_resched();
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}
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ret = mem_cgroup_try_charge(memcg,
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GFP_KERNEL & ~__GFP_NORETRY, 1);
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GFP_KERNEL & ~__GFP_NORETRY, 1);
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/*
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* In case of failure, any residual charges against
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* mc.to will be dropped by mem_cgroup_clear_mc()
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* later on.
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*/
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if (ret)
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if (ret)
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/* mem_cgroup_clear_mc() will do uncharge later */
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return ret;
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return ret;
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mc.precharge++;
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mc.precharge++;
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cond_resched();
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}
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}
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return ret;
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return 0;
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}
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}
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/**
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/**
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