From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f53.google.com (mail-ej1-f53.google.com [209.85.218.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 80D3F22B5AD for ; Thu, 16 Jan 2025 15:08:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737040141; cv=none; b=vAN52Ny0BwaNwY0t78+SMQ4XCc+Y71U16QiNTcA9P9whsmkzagLAtDSMDcfu0lc495c7/lAWc8fjoezQbjYieUfLLNd8ljebQ6h54L+zQadkKRU80sXxsQ9Djn6H65IbO9B/dJ+yZ/9A+ioezTgD45txTcRt54AHm34I8fWXtPs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737040141; c=relaxed/simple; bh=l1dPyhAH0XGedLneC12sZTIuBPdTn0qvEjkH/ggqgoQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DFzYS6ccNNWHeFJ/gA2Oxjelo5ET2sw25bgLCZ9jW6Bq0Y6WTYwXDxXB8bNV9bs+EQK+v3ZmLcRsievglGx4a1Z62THN3BdQVWnnwG7uPn6sn6ocQL3lAqhyGoqNaAVDPzzTDk9AZsqAr5cjz9gcUTxdHV9kqq0p7zX/k104bpQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=H0ubxWuE; arc=none smtp.client-ip=209.85.218.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="H0ubxWuE" Received: by mail-ej1-f53.google.com with SMTP id a640c23a62f3a-aaecf50578eso235258866b.2 for ; Thu, 16 Jan 2025 07:08:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1737040138; x=1737644938; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=yreeh01zzKDusWkdic+oOFQVMCmFSlK2ta/Ldjvs9f8=; b=H0ubxWuEVi5Qbsve/Ax3CqR37Eyx4j/YFCHBB+UgRkFkI3qw5SWdNZ6HGKBxMNlIRi RwvBk+GiJu0LjpurzUxiv7nFBOkBJaq1u5n2kci7z3vCGnQDhoFMeJk0OOgu3ISMKT6z vcMX9sPNzF1hTmYeHD1zJnvg+NjMM9GWi3Ish7LIkZcQGbDVcagjQAtYFw8WJvRrzwwW dySZ5eBWVEEgg+qvCjl9B2D2QjJ3L28k8ryLNE8tSLh9T1XyvjUrJCIfA0iIXkwAnp4l 6+LTsiwU2WOWX0EBvUP71e1N0RnYfRoyYyI1usg21pozhW0jqwEm0lFQGNQgA+3zR7Wp WaMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737040138; x=1737644938; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=yreeh01zzKDusWkdic+oOFQVMCmFSlK2ta/Ldjvs9f8=; b=IfxHNS3Kp7z12HALwDKOoiHXQ5TZREt9LepOcqGQHt3jCsn7AfBLzVL2PEECybQcK6 /bJ7jhnD+ewcCyq271x+WaVyzMQpVQe8nlhudAoCOnOkCBDSF5rEVPOIhk6IKe8fsAoN yY+Rh266UeDv+PtGJUZr5mHUIWulXCMr5PCIHXXOKnNqT0kZI8KZ7PfJhtk/0cNBVdkZ 5/0RMyssCYVKlsW4rDsH6icmbmuNaHiTkffwIHM8cNoBWB3XL36KHHoCjDXNpKt7Zji6 34GfQz7zYFbcltQ0e/gCRUho2LQRTKoyjR6YNp6vn6y3BcgkUGHZD7dUXzaI1cmslI01 XUMA== X-Forwarded-Encrypted: i=1; AJvYcCVJtfqq6IjYEMFeumVWF7M+UIjWspAbOhhfVv3WovLFJqqzepFg+uBqLorW3WgaAiLlCRyfCB3LJIIgd0c=@vger.kernel.org X-Gm-Message-State: AOJu0Yw/ZWRq/sMTu71hFfByMfVklXogzMeEyIHv8CXdkboic6agWd47 xejeO5VLsKSJvRX7+DbzCit4y0nX7LWbdn7vIm2trLd1Y/lpdVWczYqkbXunU88= X-Gm-Gg: ASbGncsrZIILPfKBPj9mjuRGXfuarshHUlrPLXy1zylAYOH91urG9XqHL94GZoe3OUF cRw6xKekyLfVDuAqAnMtM2ABdYJF0etApoW7Q34r2bewsrLTX0Wfamcmsb7BwPoIM3NsiJ1+l6b JM/sHck9BgcMAh32b1TOFOmkgJsclLEtpTwAv6RWdW9xhtmkuUVNqNFIhSKfR+Ad0hzzwa20TO+ xn6/oLMnpfB9dTAZUnRE/0DvHSTSVKcNG/ROtxlYu+Mwv72GaG5L90/ESyY+A== X-Google-Smtp-Source: AGHT+IHO11C/grQNmeI/BnNfeeb16Ic8waY3/YPL+ofGtbtLY/uULgkCfkcoFJu1N6Ophfgjg8YSnA== X-Received: by 2002:a17:906:f582:b0:aab:7507:7a94 with SMTP id a640c23a62f3a-ab2ab55970fmr3035731766b.16.1737040137682; Thu, 16 Jan 2025 07:08:57 -0800 (PST) Received: from [192.168.0.20] ([212.21.159.176]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab384d2cfc2sm8218166b.82.2025.01.16.07.08.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jan 2025 07:08:57 -0800 (PST) Message-ID: <8cf5b264-68be-42b8-b435-79b8d682fd7b@suse.com> Date: Thu, 16 Jan 2025 17:08:55 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/fred: Optimize the FRED entry by prioritizing high-probability event dispatching To: Ethan Zhao , linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: tglx@linutronix.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, xin@zytor.com, andrew.cooper3@citrix.com, mingo@redhat.com, bp@alien8.de, etzhao@outlook.com References: <20250116065145.2747960-1-haifeng.zhao@linux.intel.com> From: Nikolay Borisov Content-Language: en-US In-Reply-To: <20250116065145.2747960-1-haifeng.zhao@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 16.01.25 г. 8:51 ч., Ethan Zhao wrote: > External interrupts (EVENT_TYPE_EXTINT) and system calls (EVENT_TYPE_OTHER) > occur more frequently than other events in a typical system. Prioritizing > these events saves CPU cycles and optimizes the efficiency of performance- > critical paths. > Can you also include some performance numbers? > Signed-off-by: Ethan Zhao > --- > base commit: 619f0b6fad524f08d493a98d55bac9ab8895e3a6 > --- > arch/x86/entry/entry_fred.c | 25 +++++++++++++++++++------ > 1 file changed, 19 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c > index f004a4dc74c2..591f47771ecf 100644 > --- a/arch/x86/entry/entry_fred.c > +++ b/arch/x86/entry/entry_fred.c > @@ -228,9 +228,18 @@ __visible noinstr void fred_entry_from_user(struct pt_regs *regs) > /* Invalidate orig_ax so that syscall_get_nr() works correctly */ > regs->orig_ax = -1; > > - switch (regs->fred_ss.type) { > - case EVENT_TYPE_EXTINT: > + if (regs->fred_ss.type == EVENT_TYPE_EXTINT) > return fred_extint(regs); > + else if (regs->fred_ss.type == EVENT_TYPE_OTHER) > + return fred_other(regs); > + > + /* > + * Dispatch EVENT_TYPE_EXTINT and EVENT_TYPE_OTHER(syscall) type events > + * first due to their high probability and let the compiler create binary search > + * dispatching for the remaining events > + */ nit: At least to me it makes sense to have the comment above the 'if' so that the flow is linear. > + > + switch (regs->fred_ss.type) { > case EVENT_TYPE_NMI: > if (likely(regs->fred_ss.vector == X86_TRAP_NMI)) > return fred_exc_nmi(regs); > @@ -245,8 +254,6 @@ __visible noinstr void fred_entry_from_user(struct pt_regs *regs) > break; > case EVENT_TYPE_SWEXC: > return fred_swexc(regs, error_code); > - case EVENT_TYPE_OTHER: > - return fred_other(regs); > default: break; > } > > @@ -260,9 +267,15 @@ __visible noinstr void fred_entry_from_kernel(struct pt_regs *regs) > /* Invalidate orig_ax so that syscall_get_nr() works correctly */ > regs->orig_ax = -1; > > - switch (regs->fred_ss.type) { > - case EVENT_TYPE_EXTINT: > + if (regs->fred_ss.type == EVENT_TYPE_EXTINT) > return fred_extint(regs); > + > + /* > + * Dispatch EVENT_TYPE_EXTINT type event first due to its high probability > + * and let the compiler do binary search dispatching for the other events > + */ > + > + switch (regs->fred_ss.type) { > case EVENT_TYPE_NMI: > if (likely(regs->fred_ss.vector == X86_TRAP_NMI)) > return fred_exc_nmi(regs);