netdev - Re: [PATCH v5] posix-timers: add multi_clock

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Message-ID: <875y04kroz.ffs@tglx>
Date: Mon, 08 Jan 2024 12:09:00 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Sagi Maimon <maimon.sagi@...il.com>, richardcochran@...il.com,
 luto@...nel.org, datglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, arnd@...db.de,
 geert@...ux-m68k.org, peterz@...radead.org, hannes@...xchg.org,
 sohil.mehta@...el.com, rick.p.edgecombe@...el.com, nphamcs@...il.com,
 palmer@...ive.com, maimon.sagi@...il.com, keescook@...omium.org,
 legion@...nel.org, mark.rutland@....com
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
 linux-arch@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v5] posix-timers: add multi_clock_gettime system call

On Tue, Jan 02 2024 at 11:18, Sagi Maimon wrote:
> Some user space applications need to read some clocks.
> Each read requires moving from user space to kernel space.
> The syscall overhead causes unpredictable delay between N clocks reads
> Removing this delay causes better synchronization between N clocks.

As I explained to you before: This is wishful thinking.

There is absolutely no guarantee that the syscall will yield better
results. It might on average, but that's a useless measure.

You also still fail to explain what this is going to solve and how it's
used.

> Some user space applications need to read some clocks.

Is just not an explanation at all.

Thanks,

        tglx