From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EFCF31A9B3B for ; Tue, 28 Jan 2025 15:30:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738078257; cv=none; b=qPqHTAnZqZBxR24s6eH7fB4wKZxWeE7qqP090+4OA60o673VdxjUKjTYQDjn1IVJezWmgSicNJT5+bE29Pp0xqFk+snyig4NGm2dYWLkkaPLFJgP855CUiXaxdMQA4DHTdmpKWhC6vzhgGnF+xYvDn/xCmgSNqPJyKIBdkyJ/TQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738078257; c=relaxed/simple; bh=AtxV5mlsUBDXUDuOZCXYwx5qww0t4tsSrMrgwxeDwrE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rSzvP84o0Q08f5ejb87QWawarPtUjJ16c0HRf3C30i1I0+NP7iCTCyW6suN6PByBqgmqL+G0k59SR9qqJZ1jn/QBDkWNYHyoAAc6DxSoVkNGwHDD+L3/XAtukWMcqO/kw1x1C8/L9BUKQ6z61Pg3O4sxMRpyvJyiobLsiAJDagQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ivdYqZiY; arc=none smtp.client-ip=91.218.175.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ivdYqZiY" Date: Tue, 28 Jan 2025 15:30:38 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1738078243; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MpQv8Hh0xINXsVuX3lZlqa25GjQTW93nhOM7BZmZ9s0=; b=ivdYqZiY5EgeWAuXkLXRy8MtRDyIJ79frDYwuNdm9/VXZwFzq/49VMduUCcL3QzJC/rTIf ez0I2MKAQCbzh3ZFiebLpUNpwDnOzYHl0CQlFY6vP8d8ZhUIkyv1tigrh+tii+nfrk956g DClZGfQs/DfeQtemfy/ooU73tywvMj4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yosry Ahmed To: Vlastimil Babka Cc: Andrew Morton , Vitaly Wool , Miaohe Lin , Johannes Weiner , Nhat Pham , Chengming Zhou , Huacai Chen , Seth Jennings , Dan Streetman , WANG Xuerui , linux-mm@kvack.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev Subject: Re: [PATCH 1/2] mm: zbud: deprecate CONFIG_ZBUD Message-ID: References: <42b24914-719a-4ff1-9d77-f6517717344f@suse.cz> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42b24914-719a-4ff1-9d77-f6517717344f@suse.cz> X-Migadu-Flow: FLOW_OUT On Tue, Jan 28, 2025 at 11:21:10AM +0100, Vlastimil Babka wrote: > On 1/28/25 00:58, Yosry Ahmed wrote: > > The zbud compressed pages allocator is rarely used, most users use > > zsmalloc. zbud consumes much more memory (only stores 1 or 2 compressed > > pages per physical page). The only advantage of zbud is a marginal > > performance improvement that by no means justify the memory overhead. > > > > Historically, zsmalloc had significantly worse latency than zbud and > > z3fold but offered better memory savings. This is no longer the case as > > shown by a simple recent analysis [1]. In a kernel build test on tmpfs > > in a limited cgroup, zbud 2-3% less time than zsmalloc, but at the cost > > of using ~32% more memory (1.5G vs 1.13G). The tradeoff does not make > > sense for zbud in any practical scenario. > > > > The only alleged advantage of zbud is not having the dependency on > > CONFIG_MMU, but CONFIG_SWAP already depends on CONFIG_MMU anyway, and > > zbud is only used by zswap. > > > > Following in the footsteps of [2], which deprecated z3fold, deprecated > > zbud as planned and remove it in a few cycles if no objections are > > raised from active users. > > > > Rename the user-visible config options so that users with CONFIG_ZBUD=y > > get a new prompt with explanation during make oldconfig. Also, remove > > CONFIG_ZBUD from defconfig. > > > > [1]https://lore.kernel.org/lkml/CAJD7tkbRF6od-2x_L8-A1QL3=2Ww13sCj4S3i4bNndqF+3+_Vg@mail.gmail.com/ > > [2]https://lore.kernel.org/lkml/20240904233343.933462-1-yosryahmed@google.com/ > > > > Signed-off-by: Yosry Ahmed > > Seems weird not to Cc the folks listed in MAINTAINERS for ZBUD? Unless their > addresses are known to bounce? Ugh I had them in the CC list, but I played around with it and probably lost them :/ Seth, Dan, apologies. > And ZRAM maintainers should also be Ccd? ZRAM does not use zbud, I can definitely CC them but I don't want to be a source of noise :)