From: Jens Axboe <axboe@kernel.dk>
To: Roman Penyaev <rpenyaev@suse.de>
Cc: Azat Khuzhin <azat@libevent.org>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 00/13] epoll: support pollable epoll from userspace
Date: Fri, 31 May 2019 08:48:55 -0600 [thread overview]
Message-ID: <a2a88f4f-d104-f565-4d6e-1dddc7f79a05@kernel.dk> (raw)
In-Reply-To: <20190516085810.31077-1-rpenyaev@suse.de>
On 5/16/19 2:57 AM, Roman Penyaev wrote:
> Hi all,
>
> This is v3 which introduces pollable epoll from userspace.
>
> v3:
> - Measurements made, represented below.
>
> - Fix alignment for epoll_uitem structure on all 64-bit archs except
> x86-64. epoll_uitem should be always 16 bit, proper BUILD_BUG_ON
> is added. (Linus)
>
> - Check pollflags explicitly on 0 inside work callback, and do nothing
> if 0.
>
> v2:
> - No reallocations, the max number of items (thus size of the user ring)
> is specified by the caller.
>
> - Interface is simplified: -ENOSPC is returned on attempt to add a new
> epoll item if number is reached the max, nothing more.
>
> - Alloced pages are accounted using user->locked_vm and limited to
> RLIMIT_MEMLOCK value.
>
> - EPOLLONESHOT is handled.
>
> This series introduces pollable epoll from userspace, i.e. user creates
> epfd with a new EPOLL_USERPOLL flag, mmaps epoll descriptor, gets header
> and ring pointers and then consumes ready events from a ring, avoiding
> epoll_wait() call. When ring is empty, user has to call epoll_wait()
> in order to wait for new events. epoll_wait() returns -ESTALE if user
> ring has events in the ring (kind of indication, that user has to consume
> events from the user ring first, I could not invent anything better than
> returning -ESTALE).
>
> For user header and user ring allocation I used vmalloc_user(). I found
> that it is much easy to reuse remap_vmalloc_range_partial() instead of
> dealing with page cache (like aio.c does). What is also nice is that
> virtual address is properly aligned on SHMLBA, thus there should not be
> any d-cache aliasing problems on archs with vivt or vipt caches.
Why aren't we just adding support to io_uring for this instead? Then we
don't need yet another entirely new ring, that's is just a little
different from what we have.
I haven't looked into the details of your implementation, just curious
if there's anything that makes using io_uring a non-starter for this
purpose?
--
Jens Axboe
next prev parent reply other threads:[~2019-05-31 14:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-16 8:57 [PATCH v3 00/13] epoll: support pollable epoll from userspace Roman Penyaev
2019-05-16 8:57 ` [PATCH v3 01/13] epoll: move private helpers from a header to the source Roman Penyaev
2019-05-16 8:57 ` [PATCH v3 02/13] epoll: introduce user structures for polling from userspace Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 03/13] epoll: allocate user header and user events ring " Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 04/13] epoll: some sanity flags checks for epoll syscalls " Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 05/13] epoll: offload polling to a work in case of epfd polled " Roman Penyaev
2019-05-21 7:51 ` Eric Wong
2019-05-22 12:54 ` Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 06/13] epoll: introduce helpers for adding/removing events to uring Roman Penyaev
2019-05-31 9:55 ` Peter Zijlstra
2019-05-31 11:24 ` Roman Penyaev
2019-05-31 13:11 ` Peter Zijlstra
2019-05-31 9:56 ` Peter Zijlstra
2019-05-31 11:15 ` Roman Penyaev
2019-05-31 12:53 ` Peter Zijlstra
2019-05-31 14:28 ` Roman Penyaev
2019-05-31 16:53 ` Peter Zijlstra
2019-05-31 12:56 ` Peter Zijlstra
2019-05-31 14:21 ` Roman Penyaev
2019-05-31 16:51 ` Peter Zijlstra
2019-05-31 18:58 ` Roman Penyaev
2019-06-03 9:09 ` Peter Zijlstra
2019-06-03 10:02 ` Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 07/13] epoll: call ep_add_event_to_uring() from ep_poll_callback() Roman Penyaev
2019-05-31 9:56 ` Peter Zijlstra
2019-05-31 11:22 ` Roman Penyaev
2019-05-31 13:05 ` Peter Zijlstra
2019-05-31 15:05 ` Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 08/13] epoll: support polling from userspace for ep_insert() Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 09/13] epoll: support polling from userspace for ep_remove() Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 10/13] epoll: support polling from userspace for ep_modify() Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 11/13] epoll: support polling from userspace for ep_poll() Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 12/13] epoll: support mapping for epfd when polled from userspace Roman Penyaev
2019-05-16 8:58 ` [PATCH v3 13/13] epoll: implement epoll_create2() syscall Roman Penyaev
2019-05-16 10:03 ` Arnd Bergmann
2019-05-16 10:20 ` Roman Penyaev
2019-05-16 10:57 ` Arnd Bergmann
2019-05-22 2:33 ` Andrew Morton
2019-05-22 9:11 ` Roman Penyaev
2019-05-22 11:14 ` Arnd Bergmann
2019-05-22 18:36 ` Andrew Morton
2019-05-31 9:55 ` [PATCH v3 00/13] epoll: support pollable epoll from userspace Peter Zijlstra
2019-05-31 14:48 ` Jens Axboe [this message]
2019-05-31 16:02 ` Roman Penyaev
2019-05-31 16:54 ` Jens Axboe
2019-05-31 19:45 ` Roman Penyaev
2019-05-31 21:09 ` Jens Axboe
2019-06-05 6:17 ` Roman Penyaev
2019-05-31 16:33 ` Peter Zijlstra
2019-05-31 18:50 ` Roman Penyaev
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