linux-kernel - Re: [linus:master] [mm] f95bdb700b: stress-ng.ramfs.ops_per

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Date:   Tue, 30 May 2023 11:07:29 +0800
From:   Qi Zheng <qi.zheng@...ux.dev>
To:     paulmck@...nel.org, Kirill Tkhai <tkhai@...ru>
Cc:     RCU <rcu@...r.kernel.org>, Yujie Liu <yujie.liu@...el.com>,
        oe-lkp@...ts.linux.dev, lkp@...el.com,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Christian König <christian.koenig@....com>,
        David Hildenbrand <david@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Yang Shi <shy828301@...il.com>, linux-mm@...ck.org,
        ying.huang@...el.com, feng.tang@...el.com, fengwei.yin@...el.com
Subject: Re: [linus:master] [mm] f95bdb700b: stress-ng.ramfs.ops_per_sec
 -88.8% regression

Hi,

On 2023/5/29 20:51, Paul E. McKenney wrote:
> On Mon, May 29, 2023 at 10:39:21AM +0800, Qi Zheng wrote:

[...]

>>
>> Thanks for such a detailed explanation.
>>
>> Now I think we can continue to try to complete the idea[1] from
>> Kirill Tkhai. The patch moves heavy synchronize_srcu() to delayed
>> work, so it doesn't affect on user-visible unregistration speed.
>>
>> [1]. https://lore.kernel.org/lkml/153365636747.19074.12610817307548583381.stgit@localhost.localdomain/
> 
> A blast from the past!  ;-)
> 
> But yes, moving the long-latency synchronize_srcu() off the user-visible
> critical code path can be even better.

Yeah, I applied these patches  ([PATCH RFC 04/10]~[PATCH RFC 10/10],
with few conflicts), the ops/s does get back to the previous levels.

I'll continue updating this patchset after doing more testing.

Thanks,
Qi

> 
> 							Thanx, Paul