From: Andreas Mohr <andi@lisas.de>
To: Andreas Mohr <andi@lisas.de>
Cc: Dave Hansen <dave.hansen@intel.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
linux-kernel@vger.kernel.org, rafael@kernel.org, lenb@kernel.org,
linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org,
dave.hansen@linux.intel.com, bp@alien8.de, tglx@linutronix.de,
puwen@hygon.cn, mario.limonciello@amd.com, peterz@infradead.org,
rui.zhang@intel.com, gpiccoli@igalia.com,
daniel.lezcano@linaro.org, ananth.narayan@amd.com,
gautham.shenoy@amd.com, Calvin Ong <calvin.ong@amd.com>,
stable@vger.kernel.org, regressions@lists.linux.dev
Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture
Date: Thu, 22 Sep 2022 22:10:21 +0200 [thread overview]
Message-ID: <YyzBLc+OFIN2BMz5@rhlx01.hs-esslingen.de> (raw)
In-Reply-To: <Yyy6l94G0O2B7Yh1@rhlx01.hs-esslingen.de>
On Thu, Sep 22, 2022 at 09:42:15PM +0200, Andreas Mohr wrote:
> So one can see where my profiling effort went
> (*optimizing* things, not degrading them)
> --> hints that current Zen3-originating effort is not
> about a regression in the "regression bug" sense -
> merely a (albeit rather appreciable/sizeable... congrats!)
> performance deterioration vs.
> an optimal (currently non-achieved) software implementation state
> (also: of PORT-based handling [vs. MWAIT], mind you!).
I'd like to add a word of caution here:
AFAIK power management (here: ACPI Cx) handling generally is
about a painful *tradeoff* between
achieving best-possible performance (that's
the respectable Zen3 32MB/s vs. 33MB/s argument) and
achieving maximum power savings.
We all know that one can configure the system for
non-idle mode (idle=poll cmdline?) and
achieve record numbers in performance (...*and* power consumption - ouch!).
Current decision/implementation aspects AFAICS:
- why is the Zen3 config used here choosing
less-favourable(?) PORT-based operation mode?
- Zen3 is said to not have the STPCLK# issue
(- but then what about other more modern chipsets?)
--> we need to achieve (hopefully sufficiently precisely) a solution which
takes into account Zen3 STPCLK# improvements while
preserving "accepted" behaviour/requirements on *all* STPCLK#-hampered chipsets
("STPCLK# I/O wait is default/traditional handling"?).
Greetings
Andreas Mohr
--
GNU/Linux. It's not the software that's free, it's you.
next prev parent reply other threads:[~2022-09-22 20:10 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 6:36 [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture K Prateek Nayak
2022-09-21 8:47 ` Borislav Petkov
2022-09-21 10:39 ` K Prateek Nayak
2022-09-21 13:10 ` Borislav Petkov
2022-09-21 14:15 ` Dave Hansen
2022-09-21 19:51 ` Borislav Petkov
2022-09-21 19:55 ` Limonciello, Mario
2022-09-22 3:58 ` Ananth Narayan
2022-09-22 5:44 ` K Prateek Nayak
[not found] ` <20220923160106.9297-1-ermorton@ericmoronsm1mbp.amd.com>
2022-09-23 16:15 ` Ananth Narayan
2022-09-21 15:00 ` Peter Zijlstra
2022-09-21 19:48 ` Borislav Petkov
2022-09-22 8:17 ` Peter Zijlstra
2022-09-22 15:21 ` Rafael J. Wysocki
2022-09-22 15:36 ` Borislav Petkov
2022-09-22 15:53 ` Rafael J. Wysocki
2022-09-22 16:36 ` Dave Hansen
2022-09-22 16:44 ` Dave Hansen
2022-09-22 16:54 ` K Prateek Nayak
2022-09-22 17:01 ` Dave Hansen
2022-09-22 17:48 ` Limonciello, Mario
2022-09-22 18:17 ` Dave Hansen
2022-09-22 18:28 ` Limonciello, Mario
2022-09-23 11:47 ` Ananth Narayan
2022-09-22 19:42 ` Andreas Mohr
2022-09-22 20:10 ` Andreas Mohr [this message]
2022-09-22 21:21 ` Dave Hansen
2022-09-22 21:38 ` Limonciello, Mario
2022-09-23 7:42 ` Peter Zijlstra
2022-09-23 7:57 ` Peter Zijlstra
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