From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 0FC09430E4; Wed, 23 Aug 2023 18:03:06 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 0FB9B43036; Wed, 23 Aug 2023 18:03:06 +0200 (CEST) Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by mails.dpdk.org (Postfix) with ESMTP id 1D2A540223 for ; Wed, 23 Aug 2023 18:03:05 +0200 (CEST) Received: by linux.microsoft.com (Postfix, from userid 1086) id 6A72C2127C69; Wed, 23 Aug 2023 09:03:04 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 6A72C2127C69 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1692806584; bh=zioJRX1Fu4Thrh9bRniyeCALrEoDDwu1btJd+UQsebY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M8CPwyX0e778Qwz6W9Apjg3Qr/FRBIdntWQVFsbRZ8CYCHKF93BFUNKWPHcXY5FAq q+lItjx2P8NBbeUQJmN8GJEkChC4SZCPyjcl82189o8MYE6/vkIBhQ+IK4Adw13bC8 xzCPH3ouLSHna8Nou7i+aObau2UVBDmlfILBGvXI= Date: Wed, 23 Aug 2023 09:03:04 -0700 From: Tyler Retzlaff To: Ferruh Yigit Cc: Konstantin Ananyev , Bruce Richardson , Konstantin Ananyev , "Tummala, Sivaprasad" , "david.hunt@intel.com" , "anatoly.burakov@intel.com" , "david.marchand@redhat.com" , "thomas@monjalon.net" , "dev@dpdk.org" Subject: Re: [PATCH v5 3/3] power: amd power monitor support Message-ID: <20230823160304.GA22267@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> References: <20230418082529.544777-2-sivaprasad.tummala@amd.com> <20230816185959.1331336-1-sivaprasad.tummala@amd.com> <20230816185959.1331336-3-sivaprasad.tummala@amd.com> <20230816192758.GA12453@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> <92e7bd2e-b799-9658-c90e-f50638c6fdbd@amd.com> <35925f36-ccde-f632-8df2-f7d20e0f95cb@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <35925f36-ccde-f632-8df2-f7d20e0f95cb@amd.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Wed, Aug 23, 2023 at 10:19:39AM +0100, Ferruh Yigit wrote: > On 8/22/2023 11:30 PM, Konstantin Ananyev wrote: > > 18/08/2023 14:48, Bruce Richardson пишет: > >> On Fri, Aug 18, 2023 at 02:25:14PM +0100, Ferruh Yigit wrote: > >>> On 8/17/2023 3:18 PM, Konstantin Ananyev wrote: > >>>> > >>>>>> Caution: This message originated from an External Source. Use > >>>>>> proper caution > >>>>>> when opening attachments, clicking links, or responding. > >>>>>> > >>>>>> > >>>>>> On Wed, Aug 16, 2023 at 11:59:59AM -0700, Sivaprasad Tummala wrote: > >>>>>>> mwaitx allows EPYC processors to enter a implementation dependent > >>>>>>> power/performance optimized state (C1 state) for a specific > >>>>>>> period or > >>>>>>> until a store to the monitored address range. > >>>>>>> > >>>>>>> Signed-off-by: Sivaprasad Tummala > >>>>>>> Acked-by: Anatoly Burakov > >>>>>>> --- > >>>>>>>   lib/eal/x86/rte_power_intrinsics.c | 77 > >>>>>>> +++++++++++++++++++++++++----- > >>>>>>>   1 file changed, 66 insertions(+), 11 deletions(-) > >>>>>>> > >>>>>>> diff --git a/lib/eal/x86/rte_power_intrinsics.c > >>>>>>> b/lib/eal/x86/rte_power_intrinsics.c > >>>>>>> index 6eb9e50807..b4754e17da 100644 > >>>>>>> --- a/lib/eal/x86/rte_power_intrinsics.c > >>>>>>> +++ b/lib/eal/x86/rte_power_intrinsics.c > >>>>>>> @@ -17,6 +17,60 @@ static struct power_wait_status { > >>>>>>>        volatile void *monitor_addr; /**< NULL if not currently > >>>>>>> sleeping > >>>>>>> */  } __rte_cache_aligned wait_status[RTE_MAX_LCORE]; > >>>>>>> > >>>>>>> +/** > >>>>>>> + * These functions uses UMONITOR/UMWAIT instructions and will > >>>>>>> enter C0.2 > >>>>>> state. > >>>>>>> + * For more information about usage of these instructions, please > >>>>>>> +refer to > >>>>>>> + * Intel(R) 64 and IA-32 Architectures Software Developer's Manual. > >>>>>>> + */ > >>>>>>> +static void intel_umonitor(volatile void *addr) { > >>>>>>> +     /* UMONITOR */ > >>>>>>> +     asm volatile(".byte 0xf3, 0x0f, 0xae, 0xf7;" > >>>>>>> +                     : > >>>>>>> +                     : "D"(addr)); > >>>>>>> +} > >>>>>>> + > >>>>>>> +static void intel_umwait(const uint64_t timeout) { > >>>>>>> +     const uint32_t tsc_l = (uint32_t)timeout; > >>>>>>> +     const uint32_t tsc_h = (uint32_t)(timeout >> 32); > >>>>>>> +     /* UMWAIT */ > >>>>>>> +     asm volatile(".byte 0xf2, 0x0f, 0xae, 0xf7;" > >>>>>>> +                     : /* ignore rflags */ > >>>>>>> +                     : "D"(0), /* enter C0.2 */ > >>>>>>> +                     "a"(tsc_l), "d"(tsc_h)); } > >>>>>> > >>>>>> question and perhaps Anatoly Burakov can chime in with expertise. > >>>>>> > >>>>>> gcc/clang have built-in intrinsics for umonitor and umwait i > >>>>>> believe as per our other > >>>>>> thread of discussion is there a benefit to also providing inline > >>>>>> assembly over just > >>>>>> using the intrinsics? I understand that the intrinsics may not > >>>>>> exist for the monitorx > >>>>>> and mwaitx below so it is probably necessary for amd. > >>>>>> > >>>>>> so the suggestion here is when they are available just use the > >>>>>> intrinsics. > >>>>>> > >>>>>> thanks > >>>>>> > >>>>> The gcc built-in functions > >>>>> __builtin_ia32_monitorx()/__builtin_ia32_mwaitx are available only > >>>>> when -mmwaitx > >>>>> is used specific for AMD platforms. On generic builds, these > >>>>> built-ins are not available and hence inline > >>>>> assembly is required here. > >>>> > >>>> Ok... but we can probably put them into a separate .c file that will > >>>> be compiled with that specific flag? > >>>> Same thing can be probably done for Intel specific instructions. > >>>> In general, I think it is much more preferable to use built-ins vs > >>>> inline assembly > >>>> (if possible off-course). > >>>> > >>> > >>> We don't compile different set of files for AMD and Intel, but there are > >>> runtime checks, so putting into separate file is not much different. > > > > Well, we probably don't compile .c files for particular vendor, but we > > definitely do compile some .c files for particular ISA extensions. > > Let say there are files in lib/acl that requires various '-mavx512*' > > flags, same for other libs and PMDs. > > So still not clear to me why same approach can't be applied to > > power_instrincts.c? > > > >>> > >>> It may be an option to always enable compiler flag (-mmwaitx), I think > >>> it won't hurt other platforms but I am not sure about implications of > >>> this to other platforms (what was the motivation for the compiler guys > >>> to enable these build-ins with specific flag?). > >>> > >>> Also this requires detecting compiler that supports 'mmwaitx' or not, > >>> etc.. > >>> > >> This is the biggest reason why we have in the past added support for > >> these > >> instructions via asm bytes rather than intrinsics. It takes a long > >> time for > >> end-user compilers, especially those in LTS releases, to get the > >> necessary > >> intrinsics. > > > > Yep, understand. > > But why then we can't have both implementations? > > Let say if WAITPKG is defined we can use builtins for > > umonitor/umwait/tpause, otherwise we fallback to inline asm implementation. > > Same story for MWAITX/monitorx. > > > > Yes this can be done, > it can be done either as different .c files per implementation, or as > #ifdef in same file. > > But eventually asm implementation is required, as fallback, and if we > will rely on asm implementation anyway, does it worth to have the > additional checks to be able to use built-in intrinsic? > > Does it helps to comment name of the built-in function to inline > assembly code, to document intention and another possible implementation? the main value of preferring intrinsics is that when they are available they also work with msvc/windows. the msvc toolchain does not support inline asm. so some of the targets have to use intrinsics because that's all there is. > > >> Consider a user running e.g. RHEL 8, who wants to take > >> advantages of the latest DPDK features; they should not be required to > >> upgrade their compiler - and possibly binutils/assembler - to do so. > >> > >> /Bruce > >