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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Roman Penyaev <rpenyaev@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Peter Zijlstra <peterz@infradead.org>,
	Azat Khuzhin <azat@libevent.org>, Eric Wong <e@80x24.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 00/14] epoll: support pollable epoll from userspace
Date: Tue, 25 Jun 2019 04:38:06 +0800	[thread overview]
Message-ID: <CAHk-=wgQaCDiH09ocVA=74ceg9XyS=kRDF5Hi=783shCaKVRWg@mail.gmail.com> (raw)
In-Reply-To: <20190624144151.22688-1-rpenyaev@suse.de>

On Mon, Jun 24, 2019 at 10:42 PM Roman Penyaev <rpenyaev@suse.de> wrote:
>
> So harvesting events from userspace gives 15% gain.  Though bench_http
> is not ideal benchmark, but at least it is the part of libevent and was
> easy to modify.
>
> Worth to mention that uepoll is very sensible to CPU, e.g. the gain above
> is observed on desktop "Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz", but on
> "Intel(R) Xeon(R) Silver 4110 CPU @ 2.10GHz" measurements are almost the
> same for both runs.

Hmm. 15% may be big in a big picture thing, but when it comes to what
is pretty much a micro-benchmark, I'm not sure how meaningful it is.

And the CPU sensitivity thing worries me. Did you check _why_ it
doesn't seem to make any difference on the Xeon 4110? Is it just
because at that point the machine has enough cores that you might as
well just sit in epoll() in the kernel and uepoll doesn't give you
much? Or is there something else going on?

Because this is a big enough change and UAPI thing that it's a bit
concerning if there isn't a clear and unambiguous win.

               Linus

  parent reply	other threads:[~2019-06-24 20:38 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-24 14:41 Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 01/14] epoll: move private helpers from a header to the source Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 02/14] epoll: introduce user structures for polling from userspace Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 03/14] epoll: allocate user header and user events ring " Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 04/14] epoll: some sanity flags checks for epoll syscalls " Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 05/14] epoll: offload polling to a work in case of epfd polled " Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 06/14] epoll: introduce helpers for adding/removing events to uring Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 07/14] epoll: call ep_add_event_to_uring() from ep_poll_callback() Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 08/14] epoll: support polling from userspace for ep_insert() Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 09/14] epoll: support polling from userspace for ep_remove() Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 10/14] epoll: support polling from userspace for ep_modify() Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 11/14] epoll: support polling from userspace for ep_poll() Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 12/14] epoll: support mapping for epfd when polled from userspace Roman Penyaev
2019-06-24 14:41 ` [PATCH v5 13/14] epoll: implement epoll_create2() syscall Roman Penyaev
2019-06-24 16:14   ` Arnd Bergmann
2019-06-24 16:25     ` Roman Penyaev
2019-06-25 18:29   ` Eric Wong
2019-06-24 14:41 ` [PATCH v5 14/14] kselftest: add uepoll-test which tests polling from userspace Roman Penyaev
2019-06-24 20:38 ` Linus Torvalds [this message]
2019-06-25 11:19   ` [PATCH v5 00/14] epoll: support pollable epoll " Roman Penyaev
2019-06-25  0:24 ` Eric Wong
2019-06-25 11:07   ` Roman Penyaev

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