linux-kernel - Re: [PATCH v3 05/13] epoll: offload polling to a work in case of epfd polled from userspace

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Message-ID: <7fced5a4f9468a273b6acb0ca0fdcfb1@suse.de>
Date:   Wed, 22 May 2019 14:54:09 +0200
From:   Roman Penyaev <rpenyaev@...e.de>
To:     Eric Wong <e@...24.org>
Cc:     Azat Khuzhin <azat@...event.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/13] epoll: offload polling to a work in case of epfd
 polled from userspace

On 2019-05-21 09:51, Eric Wong wrote:
> Roman Penyaev <rpenyaev@...e.de> wrote:
>> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
>> index 81da4571f1e0..9d3905c0afbf 100644
>> --- a/fs/eventpoll.c
>> +++ b/fs/eventpoll.c
>> @@ -44,6 +44,7 @@
>>  #include <linux/seq_file.h>
>>  #include <linux/compat.h>
>>  #include <linux/rculist.h>
>> +#include <linux/workqueue.h>
>>  #include <net/busy_poll.h>
>> 
>>  /*
>> @@ -185,6 +186,9 @@ struct epitem {
>> 
>>  	/* The structure that describe the interested events and the source 
>> fd */
>>  	struct epoll_event event;
>> +
>> +	/* Work for offloading event callback */
>> +	struct work_struct work;
>>  };
>> 
>>  /*
> 
> Can we avoid the size regression for existing epoll users?

Yeah, ->next, ->rdllink, ->ws are not used for user polling, so can hold 
work
struct and co (or pointer on container which holds work struct, if work 
struct
is huge).

--
Roman