linux-kernel - Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

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Message-ID: <20140203215151.GA25594@dcvr.yhbt.net>
Date:	Mon, 3 Feb 2014 21:51:51 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Nathaniel Yazdani <n1ght.4nd.d4y@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

Andy Lutomirski <luto@...capital.net> wrote:
> >> On 02/02/2014 06:17 PM, Nathaniel Yazdani wrote:
> > So are you saying that those features you mentioned are specifically sought
> > after for the kernel? If so I'd like to take a crack at some of them,
> > may as well
> > get some use out of my new knowledge of epoll internals :)
> 
> If by "sought after", you mean "is there at least one epoll user who
> wants them", then yes :)
> 
> I think that EPOLLET and EPOLLONESHOT are giant hacks, and that what
> everyone really wants is the ability to very efficiently toggle events
> on and off.  The ability to do it simultaneously and inexpensively
> with epoll_wait would make it happen.

Everybody using single-threaded epoll, you mean?  I suppose there's
quite a few of those.

I've pondered an epoll_xchg syscall which would behave like *BSD kevent
to satisfy single-threaded users, but never got around to it.  All my
epoll uses are multithreaded w/ oneshot nowadays, so xchg would only
save one syscall per thread.
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