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Date:   Thu, 28 Apr 2022 13:12:08 +0800
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Subject: Re: [memcg] a8c49af3be: hackbench.throughput -13.7% regression
Content-Language: en-US
To:     Shakeel Butt <shakeelb@google.com>
CC:     kernel test robot <oliver.sang@intel.com>,
        Yosry Ahmed <yosryahmed@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, <lkp@lists.01.org>,
        kernel test robot <lkp@intel.com>,
        Huang Ying <ying.huang@intel.com>,
        Feng Tang <feng.tang@intel.com>,
        Xing Zhengjun <zhengjun.xing@linux.intel.com>
References: <20220420055807.GA16310@xsang-OptiPlex-9020>
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From:   Yin Fengwei <fengwei.yin@intel.com>
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Hi Shakeel,

On 4/27/2022 1:02 PM, Shakeel Butt wrote:
> Can you to comment out the following block instead of the above line
> and see if there is any impact?

Changed the code as following:

+static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
+{
+       mod_memcg_state(memcg, MEMCG_KMEM, nr_pages);
+
+#if    0
+       if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
+               if (nr_pages > 0)
+                       page_counter_charge(&memcg->kmem, nr_pages);
+               else
+                       page_counter_uncharge(&memcg->kmem, -nr_pages);
+       }
+#endif
+}
+

The hackbench test result is 147% better:

086f694a75e1a283 cee08cab8eefaaffdec62343e8d
---------------- ---------------------------
       fail:runs  %reproduction    fail:runs
           |             |             |
       8691:15      -52942%         750:6     dmesg.timestamp:last
           :15          13%           2:6     last_state.booting
           :15          13%           2:6     last_state.is_incomplete_run
          1:15          -7%            :6     kmsg.common_interrupt:#No_irq_handler_for_vector
          2:15         -18%            :6     kmsg.timestamp:common_interrupt:#No_irq_handler_for_vector
       4656:15      -26039%         750:6     kmsg.timestamp:last
         %stddev     %change         %stddev
             \          |                \
    143619 ±  4%    +147.0%     354807 ±  2%  hackbench.throughput   <------
    475.91 ±  4%     -58.8%     196.09 ±  2%  hackbench.time.elapsed_time


Regards
Yin, Fengwei