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 6F28EC19776 for ; Fri, 28 Feb 2025 05:18:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B1096280003; Fri, 28 Feb 2025 00:18:11 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A99FD280002; Fri, 28 Feb 2025 00:18:11 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8EB6E280003; Fri, 28 Feb 2025 00:18:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 6A80B280002 for ; Fri, 28 Feb 2025 00:18:11 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id D7E5C1C692A for ; Fri, 28 Feb 2025 05:18:10 +0000 (UTC) X-FDA: 83168197140.10.8765026 Received: from mail-ed1-f48.google.com (mail-ed1-f48.google.com [209.85.208.48]) by imf22.hostedemail.com (Postfix) with ESMTP id A89FBC0007 for ; Fri, 28 Feb 2025 05:18:08 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=GAETMeJH; dmarc=none; spf=pass (imf22.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.48 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740719888; a=rsa-sha256; cv=none; b=3YpXzJu7U9TG+YhrP7+AUB5faZDNwc6JO2mtWgkVfTNKeGI5/eK9qNqPKHqPeZXBnOZyml HfyWmvj+cqeYjEedaVf9vz0DbD+nNVW2cOAqIQ1Wl/BZrTUZUOZhWCbNuvc5IzYOvmawYv q/pR8luNgWPnW5VymwSDDFbO+tJNYIQ= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=GAETMeJH; dmarc=none; spf=pass (imf22.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.48 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740719888; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=5yXmfMp+a66aju4mWW7FzXsEpdGr0D1aag/ZSeEsoTk=; b=LH1GNDeE+fNegqEdIHrv0lAVX++SPv+1VbJz8rTiHR9jNAkKP3VXY5muSdLVQ7rcCRRGw+ 2elCUV0Ir2K7ktuzqrM1l8H0S5mv2mhHCqkR9iGJgtcTB7ORdZEBMkAdpCKWt9mhuU6dEs h2s78poxdrPhi9dIOVhOREx3KBQmJYI= Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-5e033c2f106so1934423a12.3 for ; Thu, 27 Feb 2025 21:18:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; t=1740719887; x=1741324687; darn=kvack.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=5yXmfMp+a66aju4mWW7FzXsEpdGr0D1aag/ZSeEsoTk=; b=GAETMeJH4GPz0Xgm40XuGiahhZCmtTVphCT+kzO8u3Eqdb6i9JJYERKGkjuYV4cGYZ rkorm+P9bA0HebfORNRKUBFgSBeHlNfxaKjFMj/kg0j7fBz66qXRSlXKhq7O1FFdNLGn phHd5LTdt0E0ZjsRiEC2ZkOdOm1j540zu5M3M= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740719887; x=1741324687; h=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=5yXmfMp+a66aju4mWW7FzXsEpdGr0D1aag/ZSeEsoTk=; b=A2rc8itpaVWQdBIqw7IKS4FVcZzNDskHlA3PBL3BEX6OgyjJ3WAYNxnnFIUPdI5J7C hEA7qPGzyKe92FJCwdrYU3u6Qk+7b9EfrSnp+OET/FgEcpgLGSMCuxuzk6GPYa4imGF5 1kkvpfJMOyRExF7xkItDaKf7YV3uZc/7eR5piJAifgVpHC89hx3+R6Tqu18jB7uSS8JP fP5Y/IJ8kxu4fk/welKjHSLgA8uRUk70d7Rmf6rNgBEiTEyeH32y6XgiNsOu2vB+h+qJ Ny3CBXqR9LBFXDqhjfDqQYhnaoq3C3hxi9DtUWNG0GO+DrAiY+4RZRh0197fW/T357wz FCqA== X-Forwarded-Encrypted: i=1; AJvYcCUQcRFkjPZqzuFGwAFLixoelyUKyX/xpONvaArRzyeOW/icSTriKW6ka7gK+8p+LCjFrZgnf+cjtw==@kvack.org X-Gm-Message-State: AOJu0YxREjucKgExxvza0H3jLmmQPRdJkRqcqW+IsX87AvGtviYVgMoB was62GG8HmuU/5u1be134xydEeLuApckqLv+ckENAe/MXdSXM7BVZ6PoHgWOK/21szQk9c2x2Ku rvFuZgQ== X-Gm-Gg: ASbGncvNxLJGcu96BdEeUqheT+iTlPvB02CcqNWfwuEO36OzT2J1Wul1iAW0me8wB41 R/v0S9PafPRYw3WIiTb2InMOu/Y126SdOO/N+93/iE/qDM/Yp/B8DbQQm6a9QXztQIUAPUReTEl 8NeiF3Eh2+lRq7m1EmqXqHelUU/DSnuKft4rq+neMfk0Ch8xtHq+90Irgm/CHNn0W3PZP5DiUci j2ND1BeqNV6wG7K9yeRdxQQhbv9c1sGa9NWlwi//kd4zex0hwhWK8Smz/ktsHtIRERkslzyQH4r Zo7FD4Xz7B76E3GuUy/Y1CNAbswqlLfCPkVDWX1DzmhOCa013k9nxDPnV87HX/8C64gjib1/C26 v X-Google-Smtp-Source: AGHT+IEGdAUpns5pa+GdPhxEdBMIu1pal+zAjk+kOedARUqJO5CmNiBji7DtL5nw9JpcXe2+EOy2lg== X-Received: by 2002:a05:6402:3902:b0:5e0:7cc4:ec57 with SMTP id 4fb4d7f45d1cf-5e4d6b63059mr3407410a12.31.1740719886635; Thu, 27 Feb 2025 21:18:06 -0800 (PST) Received: from mail-ed1-f48.google.com (mail-ed1-f48.google.com. [209.85.208.48]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-abf0c0b9990sm229346066b.35.2025.02.27.21.18.04 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Feb 2025 21:18:05 -0800 (PST) Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-5deb956aa5eso2578712a12.2 for ; Thu, 27 Feb 2025 21:18:04 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCVrRpMtEpf1XJ5d88LVSytKkM4CoIqHL8AuDPTvQ8cyiQm3XPxsDCwP9rY/yaw/+50z1mtIo12zBg==@kvack.org X-Received: by 2002:a05:6402:2695:b0:5de:594d:e9aa with SMTP id 4fb4d7f45d1cf-5e4d6ad7683mr3024531a12.8.1740719883992; Thu, 27 Feb 2025 21:18:03 -0800 (PST) MIME-Version: 1.0 References: <20250228023043.83726-1-mathieu.desnoyers@efficios.com> <8524caa9-e1f6-4411-b86b-d9457ddb8007@efficios.com> In-Reply-To: <8524caa9-e1f6-4411-b86b-d9457ddb8007@efficios.com> From: Linus Torvalds Date: Thu, 27 Feb 2025 21:17:47 -0800 X-Gmail-Original-Message-ID: X-Gm-Features: AQ5f1JrfxM-9IRCUJ4y0kXr0sjyAxoJ14Cpfy_Qm1TIXy5Xrapi2wwGX1WZWfdo Message-ID: Subject: Re: [RFC PATCH 0/2] SKSM: Synchronous Kernel Samepage Merging To: Mathieu Desnoyers Cc: Andrew Morton , linux-kernel@vger.kernel.org, Matthew Wilcox , Olivier Dion , linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A89FBC0007 X-Stat-Signature: rat9qqpcya4bjbu3sayrazsce5rzmykh X-HE-Tag: 1740719888-152624 X-HE-Meta: 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 9gZnGFG4 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 27 Feb 2025 at 19:03, Mathieu Desnoyers wrote: > > I'd be fine with SKSM replacing KSM entirely. However, I don't > think we should try to re-implement the existing KSM userspace ABIs > over SKSM. No, absolutely. The only point (for me) for your new synchronous one would be if it replaced the kernel thread async scanning, which would make the old user space interface basically pointless. But I don't actually know who uses KSM right now. My reaction really comes from a "it's not nice code in the kernel", not from any actual knowledge of the users. Maybe it works really well in some cloud VM environment, and we're stuck with it forever. In which case I don't want to see some second different interface that just makes it all worse. Linus