Messages in this thread Patch in this message | | | Date | Thu, 2 Sep 2021 09:35:58 +0800 | From | Feng Tang <> | Subject | Re: [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression |
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On Wed, Sep 01, 2021 at 08:12:24AM -0700, Andi Kleen wrote: > Feng Tang <feng.tang@intel.com> writes: > > > > Yes, the tests I did is no matter where the 128B padding is added, the > > performance can be restored and even improved. > > I wonder if we can find some cold, rarely accessed, data to put into the > padding to not waste it. Perhaps some name strings? Or the destroy > support, which doesn't sound like its commonly used.
Yes, I tried to move 'destroy_work', 'destroy_rwork' and 'parent' over before the 'refcnt' together with some padding, it restored the performance to about 10~15% regression. (debug patch pasted below)
But I'm not sure if we should use it, before we can fully explain the regression.
Thanks, Feng
commit a308d90b0d1973eb75551540a7aa849cabc8b8af Author: Feng Tang <feng.tang@intel.com> Date: Sat Aug 14 16:18:43 2021 +0800
move the member around
Signed-off-by: Feng Tang <feng.tang@intel.com>
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index f9fb7f0..255f668 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -139,10 +139,21 @@ struct cgroup_subsys_state { /* PI: the cgroup that this css is attached to */ struct cgroup *cgroup; + struct cgroup_subsys_state *parent; + /* PI: the cgroup subsystem that this css is attached to */ struct cgroup_subsys *ss; - unsigned long pad[16]; + /* percpu_ref killing and RCU release */ + struct work_struct destroy_work; + struct rcu_work destroy_rwork; + + unsigned long pad[2]; /* 128 bytes */ /* reference count - access via css_[try]get() and css_put() */ struct percpu_ref refcnt; @@ -176,6 +187,7 @@ struct cgroup_subsys_state { */ atomic_t online_cnt; + #if 0 /* percpu_ref killing and RCU release */ struct work_struct destroy_work; struct rcu_work destroy_rwork; @@ -185,6 +197,7 @@ struct cgroup_subsys_state { * fields of the containing structure. */ struct cgroup_subsys_state *parent; + #endif }; /*
> -Andi
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