From: Sohil Mehta <sohil.mehta@intel.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "Hansen, Dave" <dave.hansen@intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Luck, Tony" <tony.luck@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
"Lutomirski, Andy" <luto@kernel.org>,
Jens Axboe <axboe@kernel.dk>,
Christian Brauner <christian@brauner.io>,
Peter Zijlstra <peterz@infradead.org>,
Shuah Khan <shuah@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Jonathan Corbet <corbet@lwn.net>,
"Raj, Ashok" <ashok.raj@intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
"Kammela, Gayatri" <gayatri.kammela@intel.com>,
"Zeng, Guang" <guang.zeng@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"Witt, Randy E" <randy.e.witt@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"Thomas, Ramesh" <ramesh.thomas@intel.com>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>
Subject: Re: [RFC PATCH 00/13] x86 User Interrupts support
Date: Thu, 23 Sep 2021 16:09:07 -0700 [thread overview]
Message-ID: <e374787c-c376-be9a-b2e1-8739b36f69fc@intel.com> (raw)
In-Reply-To: <YUxwuR4V+kwk1L34@kroah.com>
On 9/23/2021 5:19 AM, Greg KH wrote:
> On Tue, Sep 14, 2021 at 07:03:36PM +0000, Mehta, Sohil wrote:
>
> Here is the updated table:
> +---------------------+-------------------------+
> | IPC type | Relative Latency |
> | |(normalized to User IPI) |
> +---------------------+-------------------------+
> | User IPI | 1.0 |
> | User IPI (blocked) | 8.9 |
> | Signal | 14.8 |
> | Eventfd | 9.7 |
> | Pipe | 16.3 |
> | Domain | 17.3 |
> +---------------------+-------------------------+
> Relative is just that, "relative". If the real values are extremely
> tiny, then relative is just "this goes a tiny tiny bit faster than what
> you have today in eventfd", right?
>
> So how about "absolute"? What are we talking here?
Thanks Greg for reviewing the patches.
The reason I have not included absolute numbers is that on a
pre-production platform it could be misleading. The data here is more of
an approximation with the final performance expected to trend in this
direction.
I have used the term "relative" only to signify that this is comparing
User IPI with others.
Let's say, if eventfd took 9.7 usec on a system then User IPI (running)
would take 1 usec. So it would still be a 9x improvement.
But, I agree with your point. This is only a micro-benchmark performance
comparison. The overall gain in a real workload would depend on how it
uses IPC.
+---------------------+------------------------------+
| IPC type | Example Latency |
| | (micro seconds) |
+---------------------+------------------------------+
| User IPI (running) | 1.0 usec |
| User IPI (blocked) | 8.9 usec |
| Signal | 14.8 usec |
| Eventfd | 9.7 usec |
| Pipe | 16.3 usec |
| Domain | 17.3 usec |
+---------------------+------------------------------+
> And this is really only for the "one userspace task waking up another
> userspace task" policies. What real workload can actually use this?
A User IPI sender could be registered to send IPIs to multiple targets.
But, there is no broadcast mechanism, so it can only target one receiver
everytime it executes the SENDUIPI instruction.
Thanks,
Sohil
> thanks,
>
> greg k-h
next prev parent reply other threads:[~2021-09-23 23:09 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-13 20:01 [RFC PATCH 00/13] x86 User Interrupts support Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 01/13] x86/uintr/man-page: Include man pages draft for reference Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 02/13] Documentation/x86: Add documentation for User Interrupts Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 03/13] x86/cpu: Enumerate User Interrupts support Sohil Mehta
2021-09-23 22:24 ` Thomas Gleixner
2021-09-24 19:59 ` Sohil Mehta
2021-09-27 20:42 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 04/13] x86/fpu/xstate: Enumerate User Interrupts supervisor state Sohil Mehta
2021-09-23 22:34 ` Thomas Gleixner
2021-09-27 22:25 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 05/13] x86/irq: Reserve a user IPI notification vector Sohil Mehta
2021-09-23 23:07 ` Thomas Gleixner
2021-09-25 13:30 ` Thomas Gleixner
2021-09-26 12:39 ` Thomas Gleixner
2021-09-27 19:07 ` Sohil Mehta
2021-09-28 8:11 ` Thomas Gleixner
2021-09-27 19:26 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 06/13] x86/uintr: Introduce uintr receiver syscalls Sohil Mehta
2021-09-23 12:26 ` Greg KH
2021-09-24 0:05 ` Thomas Gleixner
2021-09-27 23:20 ` Sohil Mehta
2021-09-28 4:39 ` Greg KH
2021-09-28 16:47 ` Sohil Mehta
2021-09-23 23:52 ` Thomas Gleixner
2021-09-27 23:57 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 07/13] x86/process/64: Add uintr task context switch support Sohil Mehta
2021-09-24 0:41 ` Thomas Gleixner
2021-09-28 0:30 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 08/13] x86/process/64: Clean up uintr task fork and exit paths Sohil Mehta
2021-09-24 1:02 ` Thomas Gleixner
2021-09-28 1:23 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 09/13] x86/uintr: Introduce vector registration and uintr_fd syscall Sohil Mehta
2021-09-24 10:33 ` Thomas Gleixner
2021-09-28 20:40 ` Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 10/13] x86/uintr: Introduce user IPI sender syscalls Sohil Mehta
2021-09-23 12:28 ` Greg KH
2021-09-28 18:01 ` Sohil Mehta
2021-09-29 7:04 ` Greg KH
2021-09-29 14:27 ` Sohil Mehta
2021-09-24 10:54 ` Thomas Gleixner
2021-09-13 20:01 ` [RFC PATCH 11/13] x86/uintr: Introduce uintr_wait() syscall Sohil Mehta
2021-09-24 11:04 ` Thomas Gleixner
2021-09-25 12:08 ` Thomas Gleixner
2021-09-28 23:13 ` Sohil Mehta
2021-09-28 23:08 ` Sohil Mehta
2021-09-26 14:41 ` Thomas Gleixner
2021-09-29 1:09 ` Sohil Mehta
2021-09-29 3:30 ` Andy Lutomirski
2021-09-29 4:56 ` Sohil Mehta
2021-09-30 18:08 ` Andy Lutomirski
2021-09-30 19:29 ` Thomas Gleixner
2021-09-30 22:01 ` Andy Lutomirski
2021-10-01 0:01 ` Thomas Gleixner
2021-10-01 4:41 ` Andy Lutomirski
2021-10-01 9:56 ` Thomas Gleixner
2021-10-01 15:13 ` Andy Lutomirski
2021-10-01 18:04 ` Sohil Mehta
2021-10-01 21:29 ` Thomas Gleixner
2021-10-01 23:00 ` Sohil Mehta
2021-10-01 23:04 ` Andy Lutomirski
2021-09-13 20:01 ` [RFC PATCH 12/13] x86/uintr: Wire up the user interrupt syscalls Sohil Mehta
2021-09-13 20:01 ` [RFC PATCH 13/13] selftests/x86: Add basic tests for User IPI Sohil Mehta
2021-09-13 20:27 ` [RFC PATCH 00/13] x86 User Interrupts support Dave Hansen
2021-09-14 19:03 ` Mehta, Sohil
2021-09-23 12:19 ` Greg KH
2021-09-23 14:09 ` Greg KH
2021-09-23 14:46 ` Dave Hansen
2021-09-23 15:07 ` Greg KH
2021-09-23 23:24 ` Sohil Mehta
2021-09-23 23:09 ` Sohil Mehta [this message]
2021-09-24 0:17 ` Sohil Mehta
2021-09-23 14:39 ` Jens Axboe
2021-09-29 4:31 ` Andy Lutomirski
2021-09-30 16:30 ` Stefan Hajnoczi
2021-09-30 17:24 ` Sohil Mehta
2021-09-30 17:26 ` Andy Lutomirski
2021-10-01 16:35 ` Stefan Hajnoczi
2021-10-01 16:41 ` Richard Henderson
2021-09-30 16:26 ` Stefan Hajnoczi
2021-10-01 0:40 ` Sohil Mehta
2021-10-01 8:19 ` Pavel Machek
2021-11-18 22:19 ` Sohil Mehta
2021-11-16 3:49 ` Prakash Sangappa
2021-11-18 21:44 ` Sohil Mehta
2021-12-22 16:17 ` Chrisma Pakha
2022-01-07 2:08 ` Sohil Mehta
2022-01-17 1:14 ` Chrisma Pakha
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