From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26C8EC48291 for ; Fri, 2 Feb 2024 15:42:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9FF486B0074; Fri, 2 Feb 2024 10:42:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 987BD6B007B; Fri, 2 Feb 2024 10:42:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 801176B007E; Fri, 2 Feb 2024 10:42:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 6A7086B0074 for ; Fri, 2 Feb 2024 10:42:24 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id D8C48A2626 for ; Fri, 2 Feb 2024 15:42:23 +0000 (UTC) X-FDA: 81747280566.14.9CC5D5C Received: from mail-ej1-f52.google.com (mail-ej1-f52.google.com [209.85.218.52]) by imf06.hostedemail.com (Postfix) with ESMTP id 04E65180002 for ; Fri, 2 Feb 2024 15:42:21 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=A6YOEKyV; dmarc=none; spf=pass (imf06.hostedemail.com: domain of alexghiti@rivosinc.com designates 209.85.218.52 as permitted sender) smtp.mailfrom=alexghiti@rivosinc.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706888542; a=rsa-sha256; cv=none; b=KOEV67K7/BZLbmpNbZMezh7L1PvhyfJej0A88+bjVEiooO/bs8wf2csq+33D2tyRDgNiAK 42HYqJJ63Cm/yguRRm8eUrPbMhj/qzg6mFrlcV9vn2GhKk2PUdy2wZeV+/nEmKzgPGKylB 4q8T2hdSiisBITYCdfEArAlMVdHTABc= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=A6YOEKyV; dmarc=none; spf=pass (imf06.hostedemail.com: domain of alexghiti@rivosinc.com designates 209.85.218.52 as permitted sender) smtp.mailfrom=alexghiti@rivosinc.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706888542; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kogXmKbjRAlSmOtOOnfMNwgduTqXGjDmhtreItP19dw=; b=3gabR9ngjYAy7S8q9CcDLWs/mz+T7dVFa3xQkzw3b3yevvugb/A56t1RSBXgg2+JZ3UB/o ZJJzOUayDr8qYaaaJm7gE95aW/fETC2UEucZzlhKplBQ+tXrZHaMiQUINwH2Np6D9fgST3 1fjNR+cqPANvtBXhz7vjt/3+VUSqIRs= Received: by mail-ej1-f52.google.com with SMTP id a640c23a62f3a-a350bfcc621so275184166b.0 for ; Fri, 02 Feb 2024 07:42:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1706888540; x=1707493340; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=kogXmKbjRAlSmOtOOnfMNwgduTqXGjDmhtreItP19dw=; b=A6YOEKyVq+vi9KMmlt543xAv8xsjLeATdZfMPJc8tqM/CCAp4ByJaeTrC3/c5nL1dV WNPXbtVyPin35czdDjJ0wRiO4A8Q54cZypjuCOYCIQ+4cDnXf3fmljKV1ppxNlxZlG0T 2GVCGIfgUFZuFqdCXqeSTJFS5mnJyWOm6syxTJzw5jQT95bUiaBr5hkd6HleL3lp6QBA rUGh6vUsUTxc+DnM+FaDjPPbiSK5MzqX0sBKwWHM35epP8PbUDXx23fuUlC8OlfZ0iSO mrVryJGi2QxB2QQQ5O6o7zHHywhsk02R/u0iCjA6Dey70xqKBlwwQRSVnIeMNnqRJaaF RCXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706888540; x=1707493340; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=kogXmKbjRAlSmOtOOnfMNwgduTqXGjDmhtreItP19dw=; b=dI0cqZFfbo/SUL1Le6cK3dXW61+7agzc50Em2nDd0lFw+xFe7asdfoz2thI9VyvzwU r396okfRr9gjKKFemUMtRCbP4tHxWu50Yk+pwRSR6/hF/gXjmrM7zyZVoFku9/tshlQM hksjxA8kRwMU3c4FDeBUnvmD/whtW11lyt53H09jvcmfHUjZ3N1v0h4Zr4QDDibT71Gn EmlWeHOgWE+asz89rMNwlbpKzZMbEUg272EZw9jRSeSpKeXSu986sJnRzYGfWWaZJcft 8gcgKwE05sU5iuimAD4H/kk4F6wYoA+VWTUc0epE1uEWgMAqn+kEGOESMkRIDlX1o9Rc rfgg== X-Gm-Message-State: AOJu0YywcQM5BEpeEY+MSemBwWFavyv4P63gkkixWkTI6caQwlLfkDrB MpZChAf5eLw1igmz7Yl3n6mkQ/WZRnJN7wh0790hUtxbo/4SOHNMhW8KV2d2boeezJBiSPQ86LT lHruVQNaBVE0BrneVqY7KhFeiIO7cVOTkOi83qg== X-Google-Smtp-Source: AGHT+IH/zecNEC28nmVGlGmSbLynz6gk5o5sKPfDBpuJdaR6b+rS66s9/R0EOFKWMVOPLIAlSXsBwV7AsTvhcGsm6n0= X-Received: by 2002:a17:906:538f:b0:a31:8ca6:dbb0 with SMTP id g15-20020a170906538f00b00a318ca6dbb0mr1676412ejo.16.1706888540289; Fri, 02 Feb 2024 07:42:20 -0800 (PST) MIME-Version: 1.0 References: <20240131155929.169961-1-alexghiti@rivosinc.com> <20240131155929.169961-5-alexghiti@rivosinc.com> In-Reply-To: From: Alexandre Ghiti Date: Fri, 2 Feb 2024 16:42:09 +0100 Message-ID: Subject: Re: [PATCH RFC/RFT v2 4/4] riscv: Stop emitting preventive sfence.vma for new userspace mappings with Svvptc To: Andrea Parri Cc: Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , Ved Shanbhogue , Matt Evans , Dylan Jhong , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 04E65180002 X-Stat-Signature: 8ttbmhou7utow3e35yb56hkrspdskywu X-HE-Tag: 1706888541-451429 X-HE-Meta: U2FsdGVkX18VNa6MeOnLCvSJ8lnxRyRn26+fn4V/bFRy/RwNq3mELsbMak0g+FgiHgwUJ2uqVLLcnLsOtRs3zLWFztlBPu2Ap7VYWiWjjTrjYnBJwV2uMYn1YCDXC2rxDHbGqusgFOJaRQAMm8m0/Uy4qFb1ohJ0L4ROpGvAwHdKOpuyvv25ElwV4iGCz+gIRir2t19fXan7tPHEf+fQ8lll1kG8/07JX7VlbMsoznqNUamlzIT0MlywHEVspMFldnekvnMk56PcCZglXKnqDGiIpLhtwkSZYOr8MhYQx+hAGrLEwYL1j1hCIMQOPzUM0YGQvbUtnqyFIEeNMoRr7jnpLeFGBSfUIQmkrbeOdHrcIzSIyXGOajYfAvPWiZs/pKMxxlOT6IHwoDsu5aq26IJmFx984ng42pRb/qYUJzx2Pp7M01AYlMuJuSl/vh8H3WTrunVyXela5wc6tlYUOsBDhq9VPNssjw4ml0dh0/sFPz6w3cAlTfQldmyr/8KRG7F3B6YLBp4UhtyK1v1tcfGg38+qQ5zI6RX9btSOJ4ONwYD0d1m98bo+AZTD5RSXn9LXe/BIYU1Bv+DiuQZUhBoG5INf/NAxp9eOUxR2isWjaJuFH6u8ywbZYls4k897oynjdVQVikUf4ni13M7A62rmODF1U1eFPBWC3jDsHp59DrJ5z+pruB7FekaCv1tXZlNqyLHwaS6MnRuGt2xgr2R3Vw8XwSJEUx7Bapy4t5BT2pmQi7NJvrn2YTR9Tnf76Ljr0t+PlR5qocBiVjYALgr0hX+hxwuQAywj2AGctSCGwzDVsdaOCrF/a6/8GpbDb+3kk+HJEE8bePsbQ49vvKpMiZ/SOPEO0KQkhOeEmzpD7/RR01uy7v9XMaoTz3W6FtI3c52L6GmdcdrWQGY62Jz5yelVn/brFPo3zLdQd+dut5Cd0fw5mLvk1YOUVTzT6cY9iTyGzgoG1trS38c Gtc0biD0 hQpOi6iNKFPxrvbiOZDKDMiqAEDdY373JcMf3rGlCQFbQufjWwGchHPIn8wqFa4ah7ws+eqw4HL6hXtgXngGwUeV+NVbSCW1yEC26flRLkv2LpJVeTGRJmboHzaFm6cd+ApQ/g5blDg3s6om6urZf3GYfXfP6TR/TTMa2TlSVLVcuF/XQM5EINYTBQzkY+FSlNXuvQyZgexyLLW9Oophu/ZOsvNepSxVDwxF6KJ6HTnjdNib0+pImjQ4hj/wwH6z3qsVRLFZSeeYhBiVSRbSyauWz94tZa+pSAnWzI5Ky3Nzsm9GCKKwH5jkzEOId+isBhm8tC+PvmJCN0aamH362XlEli7cSiC6GPn6/98gjqlGra1U= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Andrea, On Thu, Feb 1, 2024 at 4:03=E2=80=AFPM Andrea Parri wrote: > > On Wed, Jan 31, 2024 at 04:59:29PM +0100, Alexandre Ghiti wrote: > > The preventive sfence.vma were emitted because new mappings must be mad= e > > visible to the page table walker but Svvptc guarantees that xRET act as > > a fence, so no need to sfence.vma for the uarchs that implement this > > extension. > > AFAIU, your first submission shows that you don't need that xRET property= . > Similarly for other archs. What was rationale behind this Svvptc change? Actually, the ARC has just changed its mind and removed this new behaviour from the Svvptc extension, so we will take some gratuitous page faults (but that should be outliners), which makes riscv similar to x86 and arm64. > > > > This allows to drastically reduce the number of sfence.vma emitted: > > > > * Ubuntu boot to login: > > Before: ~630k sfence.vma > > After: ~200k sfence.vma > > > > * ltp - mmapstress01 > > Before: ~45k > > After: ~6.3k > > > > * lmbench - lat_pagefault > > Before: ~665k > > After: 832 (!) > > > > * lmbench - lat_mmap > > Before: ~546k > > After: 718 (!) > > This Svvptc seems to move/add the "burden" of the synchronization to xRET= : > Perhaps integrate the above counts w/ the perf gains in the cover letter? Yes, I'll copy that to the cover letter. Thanks for your interest! Alex > > Andrea