linux-kernel - Re: [RFC PATCH 1/1] epoll: use rwlock in order to reduce ep_poll

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Message-ID: <20181206030818.vu5g3edwl67tg3lc@linux-r8p5>
Date:   Wed, 5 Dec 2018 19:08:18 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Jason Baron <jbaron@...mai.com>
Cc:     Roman Penyaev <rpenyaev@...e.de>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 1/1] epoll: use rwlock in order to reduce
 ep_poll_callback() contention

>On 12/3/18 6:02 AM, Roman Penyaev wrote:

>>  		if (!ep_is_linked(epi)) {
>> -			list_add_tail(&epi->rdllink, &ep->rdllist);
>> +			/* Reverse ->ovflist, events should be in FIFO */
>> +			list_add(&epi->rdllink, &ep->rdllist);
>>  			ep_pm_stay_awake(epi);
>>  		}

This should probably a separate patch as it fixes the ordering,
regardless of the rwlock+xchg optimization.

Thanks,
Davidlohr