From: Borislav Petkov <bp@alien8.de> To: "tarumizu.kohei@fujitsu.com" <tarumizu.kohei@fujitsu.com> Cc: "catalin.marinas@arm.com" <catalin.marinas@arm.com>, "will@kernel.org" <will@kernel.org>, "tglx@linutronix.de" <tglx@linutronix.de>, "mingo@redhat.com" <mingo@redhat.com>, "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>, "x86@kernel.org" <x86@kernel.org>, "hpa@zytor.com" <hpa@zytor.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: Re: [RFC PATCH v2 0/5] Add hardware prefetch driver for A64FX and Intel processors Date: Wed, 10 Nov 2021 09:34:02 +0100 [thread overview] Message-ID: <YYuD+jRPUQrsmAkD@zn.tnic> (raw) In-Reply-To: <OSBPR01MB20370518F9296BA4302FF7DC80919@OSBPR01MB2037.jpnprd01.prod.outlook.com> On Mon, Nov 08, 2021 at 02:17:43AM +0000, tarumizu.kohei@fujitsu.com wrote: > The following performance improvements have been reported for some > Intel processors. > https://github.com/xmrig/xmrig/issues/1433#issuecomment-572126184 Yes, I know about that use case. > For these reasons, we would like to add this interface to the > upstream kernel. So put all those justifications at the beginning of your 0th message when you send a patchset so that it is clear to reviewers *why* you're doing this. The "why" is the most important - everything else comes after. > > I'm not sure about a wholly separate drivers/hwpf/ - it's not like there are > > gazillion different hw prefetch drivers. > > We created a new directory to lump multiple separate files into one > place. We don't think this is a good way. If there is any other > suitable way, we would like to change it. Well, how many prefetcher drivers will be there? On x86 there will be one per vendor, so 2-3 the most... Also, as dhansen points out, we have already /sys/devices/system/cpu/cpu*/cache so all those knobs belong there on x86. Also, I think that shoehorning all these different cache architectures and different prefetcher knobs which are available from each CPU, into a common sysfs hierarchy is going to cause a lot of ugly ifdeffery if not done right. Some caches will have control A while others won't - they will have control B so people will wonder why control A works on box B_a but not on box B_b... So we have to be very careful what we expose to userspace because it becomes an ABI which we have to support for an indefinite time. Also, if you're going to give the xmrig example, then we should involve the xmrig people and ask them whether the stuff you're exposing to userspace is good for their use case. And so on and so on... Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@alien8.de> To: "tarumizu.kohei@fujitsu.com" <tarumizu.kohei@fujitsu.com> Cc: "catalin.marinas@arm.com" <catalin.marinas@arm.com>, "will@kernel.org" <will@kernel.org>, "tglx@linutronix.de" <tglx@linutronix.de>, "mingo@redhat.com" <mingo@redhat.com>, "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>, "x86@kernel.org" <x86@kernel.org>, "hpa@zytor.com" <hpa@zytor.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: Re: [RFC PATCH v2 0/5] Add hardware prefetch driver for A64FX and Intel processors Date: Wed, 10 Nov 2021 09:34:02 +0100 [thread overview] Message-ID: <YYuD+jRPUQrsmAkD@zn.tnic> (raw) In-Reply-To: <OSBPR01MB20370518F9296BA4302FF7DC80919@OSBPR01MB2037.jpnprd01.prod.outlook.com> On Mon, Nov 08, 2021 at 02:17:43AM +0000, tarumizu.kohei@fujitsu.com wrote: > The following performance improvements have been reported for some > Intel processors. > https://github.com/xmrig/xmrig/issues/1433#issuecomment-572126184 Yes, I know about that use case. > For these reasons, we would like to add this interface to the > upstream kernel. So put all those justifications at the beginning of your 0th message when you send a patchset so that it is clear to reviewers *why* you're doing this. The "why" is the most important - everything else comes after. > > I'm not sure about a wholly separate drivers/hwpf/ - it's not like there are > > gazillion different hw prefetch drivers. > > We created a new directory to lump multiple separate files into one > place. We don't think this is a good way. If there is any other > suitable way, we would like to change it. Well, how many prefetcher drivers will be there? On x86 there will be one per vendor, so 2-3 the most... Also, as dhansen points out, we have already /sys/devices/system/cpu/cpu*/cache so all those knobs belong there on x86. Also, I think that shoehorning all these different cache architectures and different prefetcher knobs which are available from each CPU, into a common sysfs hierarchy is going to cause a lot of ugly ifdeffery if not done right. Some caches will have control A while others won't - they will have control B so people will wonder why control A works on box B_a but not on box B_b... So we have to be very careful what we expose to userspace because it becomes an ABI which we have to support for an indefinite time. Also, if you're going to give the xmrig example, then we should involve the xmrig people and ask them whether the stuff you're exposing to userspace is good for their use case. And so on and so on... Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-11-10 8:34 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-04 5:21 [RFC PATCH v2 0/5] Add hardware prefetch driver for A64FX and Intel processors Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-04 5:21 ` [RFC PATCH v2 1/5] driver: hwpf: Add hardware prefetch core driver register/unregister functions Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-04 5:21 ` [RFC PATCH v2 2/5] driver: hwpf: Add support for A64FX to hardware prefetch driver Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-04 5:21 ` [RFC PATCH v2 3/5] driver: hwpf: Add support for Intel " Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-08 1:51 ` Dave Hansen 2021-11-08 1:51 ` Dave Hansen 2021-11-09 9:44 ` tarumizu.kohei 2021-11-09 9:44 ` tarumizu.kohei 2021-11-04 5:21 ` [RFC PATCH v2 4/5] driver: hwpf: Add Kconfig/Makefile to build " Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-04 5:21 ` [RFC PATCH v2 5/5] docs: ABI: Add sysfs documentation interface of " Kohei Tarumizu 2021-11-04 5:21 ` Kohei Tarumizu 2021-11-04 14:55 ` Dave Hansen 2021-11-04 14:55 ` Dave Hansen 2021-11-08 1:29 ` tarumizu.kohei 2021-11-08 1:29 ` tarumizu.kohei 2021-11-08 1:49 ` Dave Hansen 2021-11-08 1:49 ` Dave Hansen 2021-11-09 9:41 ` tarumizu.kohei 2021-11-09 9:41 ` tarumizu.kohei 2021-11-09 17:44 ` Dave Hansen 2021-11-09 17:44 ` Dave Hansen 2021-11-10 9:25 ` tarumizu.kohei 2021-11-10 9:25 ` tarumizu.kohei 2021-11-04 15:13 ` [RFC PATCH v2 0/5] Add hardware prefetch driver for A64FX and Intel processors Borislav Petkov 2021-11-04 15:13 ` Borislav Petkov 2021-11-08 2:17 ` tarumizu.kohei 2021-11-08 2:17 ` tarumizu.kohei 2021-11-10 8:34 ` Borislav Petkov [this message] 2021-11-10 8:34 ` Borislav Petkov 2021-11-18 6:14 ` tarumizu.kohei 2021-11-18 6:14 ` tarumizu.kohei 2021-11-18 7:09 ` tarumizu.kohei 2021-11-18 7:09 ` tarumizu.kohei 2021-12-06 9:30 ` tarumizu.kohei 2021-12-06 9:30 ` tarumizu.kohei 2021-11-04 17:10 ` Peter Zijlstra 2021-11-04 17:10 ` Peter Zijlstra 2021-11-08 2:36 ` tarumizu.kohei 2021-11-08 2:36 ` tarumizu.kohei
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