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 9FB5AC3DA4A for ; Wed, 14 Aug 2024 06:04:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E0A486B0082; Wed, 14 Aug 2024 02:04:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DB97E6B0083; Wed, 14 Aug 2024 02:04:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C5A396B0085; Wed, 14 Aug 2024 02:04:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id A9BD26B0082 for ; Wed, 14 Aug 2024 02:04:04 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 08E04A0CA3 for ; Wed, 14 Aug 2024 06:04:04 +0000 (UTC) X-FDA: 82449810408.05.163790E Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) by imf09.hostedemail.com (Postfix) with ESMTP id 0623814001B for ; Wed, 14 Aug 2024 06:04:01 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=Qi5geRcj; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf09.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.214.181 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1723615384; a=rsa-sha256; cv=none; b=4mu2xf5jsrId28ofqOk+v3wEcQ5YrRi6kRNlFGl7I94JwSBQMuAATorynX5kB3s3EV3QgH ULVtPWXoTannA53Y4xBg+x9YnyFpd+4Hwk/fK8Lg42WGxCpbM3iS4kHO2NZknqrKPgkkCl XzmHQ1TkUX31jCzyiS1fDNQ21N8Ggws= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=Qi5geRcj; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf09.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.214.181 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1723615384; 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=pNj8LuYKX9xbINVTD2P2mQ4u/TEZvTfYpMXCeQReyaE=; b=rseLGWhPMjWwBYUXzDnIPHjUbSR9L0kRFyy0JFrVCbeFjKp2EYNp4xxmqhXj7NZxVQ64+M fYDNY2QcoDQIxhQPUFM5D/3w0z0JX+Phjuwo7SVN4M0CztHm8K9NFzgb8FBMoexxVhYKKP 2oc260nbVgKsmFUPHbPLgsR6AtuDxio= Received: by mail-pl1-f181.google.com with SMTP id d9443c01a7336-1fd66cddd4dso60328805ad.2 for ; Tue, 13 Aug 2024 23:04:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1723615440; x=1724220240; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=pNj8LuYKX9xbINVTD2P2mQ4u/TEZvTfYpMXCeQReyaE=; b=Qi5geRcjE+x2KdewflbnNHniPEsHF48hVTP3cin7FDqew/nnJ86I1K+2+yJrrc8nvR uH3IE/y1uHICBA4NdeBkR7PV2NyrgFVrcxSP5NuIwiRfs7P/YJZ+hZ2cBV1M4k/XGhP1 NBERskC+c0gSH8ToOIv1XsP2isZg5Od5dP3SE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723615440; x=1724220240; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=pNj8LuYKX9xbINVTD2P2mQ4u/TEZvTfYpMXCeQReyaE=; b=HQBznRoXxq2F4CCrFJ1psnW/4s6eTVIpc4smyyKHKFfdDcz8X8hV0HUOlzBOZA9LLC /OGjAOYke5r4ZZhK1p1al7QrqpbHEuiQHo7/1sN0DHj0PQK+A3iwJXe5AJc/WYqhdYIf EVLP0/+BB0ZldBZ85UJt62JNNsyj9CNigy3O6QzESCoH5Nr2uFYygWpFwxYGpOxZB/rk Txrm+jlegnGvsDjJozrqzXYDQUsDdXZjgjvJQP/xDH+aNSwENzjDhW40PkamZeQgpsse aICx2sOKePYiyuqXhW+kNsf44UUmWosmm9ZWWmxRkKLMWrhxA7+KDdR1k2nmb7YOiO0j RrPA== X-Forwarded-Encrypted: i=1; AJvYcCVwOldqeHIMhdzt2FRynMPpnFDdln7YeumriLc6kdx5MNGTqJpvdpR9c3uRITUnAfx+DVd8jrAicskwcakSYp4M/I0= X-Gm-Message-State: AOJu0YylG6VMyIjwCJyOv/SN3QyEh+/xOJ1yCzBo7doVz5h+xNQ+/+sn 1aGc2XPn3rFgcmB1Qo/Etsj/x1XT7xac4F9WIdRGQ0IlUcehMUhqBznEQvSx0Q== X-Google-Smtp-Source: AGHT+IF6nPUX3LCtvUGfeZRm+NxInxBIPLi+d3Evei1ICMnde3/q1+4sAiFuM5J9B4IoD13HbnBgBg== X-Received: by 2002:a17:903:18b:b0:1fd:a360:4469 with SMTP id d9443c01a7336-201d64880eemr22567825ad.42.1723615440421; Tue, 13 Aug 2024 23:04:00 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:1432:35df:53f:489f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-201cd1cff62sm22403315ad.292.2024.08.13.23.03.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Aug 2024 23:03:59 -0700 (PDT) Date: Wed, 14 Aug 2024 15:03:54 +0900 From: Sergey Senozhatsky To: Matthew Wilcox Cc: Sergey Senozhatsky , Yosry Ahmed , Andrew Morton , alexs@kernel.org, Vitaly Wool , Miaohe Lin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, david@redhat.com, 42.hyeyoo@gmail.com, nphamcs@gmail.com Subject: Re: [PATCH v5 00/21] mm/zsmalloc: add zpdesc memory descriptor for zswap.zpool Message-ID: <20240814060354.GC8686@google.com> References: <20240806022143.3924396-1-alexs@kernel.org> <20240806022311.3924442-1-alexs@kernel.org> <20240806123213.2a747a8321bdf452b3307fa9@linux-foundation.org> <20240807051754.GA428000@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0623814001B X-Stat-Signature: pdfmh4nxasct6rhsktb1ocdqjifuf4ha X-Rspam-User: X-HE-Tag: 1723615441-748313 X-HE-Meta: U2FsdGVkX1/P+crII2MKbAjJC2zFAWuvqq/bzL+a/JztwcPgZ6PDTp5eCrvlmB//aONvvTuCLy3XieSdtcxLaSa1LGi8DQ44JlxKXgwA+mqNiERJsPLZJ+4UDABcfXftuKw+XVvDoMDaTFSlQwduAU/adMLCoGOAs9myCHJeP7eQn4PhkLv/tNXnPz4vvEEN+2xOaSszvZU7PBVWCoe6slLRAaWapQ2JFAjI7tGmr9JMvm5gghly38uHny+DAb9nDlCe0UQy8HSIxZ1ztyjkYYl/wXslyC9syaC5xOFJMgmu/6476cHn916bPQKiadcDkv/eL+en5crPDpz4yr5cd63nMXmJtrru8ZoV1gYfPz/mATKSp5mdl7O8y7pe6wgZUSXiA/CDX2wx58gD+tRdCc2VJHqrmmoya5yIDWirZBFLc6aZaV29QOE++ZUxseLSmU2Hi7aG0qMr3oSYjqWqIoxpwBsRtAgyvGNbi1G+MCgNHD03tMTiaeJPvQ/tlawXjRZ4q/Qti/X2CMHCFI7e9mals2KIorAjXu7SyXcnfOZlXUSyi7gmCL+bTTZz62YdIwsdPNhAEdf7JIdPVTGdPAFDoE9IYMOnaljSi8ftfit6LpwtO9izmyDUWIp2kMhVZN61ZaOTT96po/7L38j2FBA8+yzXrVJjdt/z/uBZ7x5YJwAUfafCdsk6jZXqDtKr/K5/ZrFgdiThVBwVkD6L6VY99gthlupSFTZVY/nTD19EAp2CErSV5quT61Vt8TrE/XNqMJd5+BvP7qPl/XDCqKBjttWBN4crVlHt+SnDvUFcjMikcLgan1l3kSP+phBgC3FlfgKvSZof4uYw+PA6FbM2suiEukv0vYhSYacM8K88yiynUbWDFjufAog44zb8bfo22BokmCRRHn8Z+RVa1IoAvwlF/VMH9GUuyfoIJZRY72O8VuP6JDoCHydlVacIBXUClezYYkuXMQvYmA4 jRp59Gpd Qc8wPJS0sVXwyFI2zEERQSvuhpkMH08a3vb2RaaVUNVPJ00LYdzmk6rZu/tSf+bUsVIRo2VO9t9lZZXasl5aORchli46GWXh3wEwSuBJ2ViPgt5mZiBBvTDcZidMZJxzIqOZUwP6zPqrisVnMYOfYRxoubrcrzgFthNsq6ccjZmXTpmwEf2E+ff3jNn8d1zy/p3CmG6vZsVYzMHRQSEzcuJBxe4gV8xRq/lGLvp/bYf3lUJYe9Y8+asSHmnqvHuTaP409p1EYpHvVgQWjSrbVSxZsinuIqP+baHL6OfF7FMYAy5tB/4RC3/y0ENPvhcbiM2J2WR1O6yXuInM6+bKfrk05T8fCr51VWJlWult+6A84cY3DtRg44s+kRsWuECixKuevmCUJcTqWQBEzLadSnCscyYCA2h3cv4sdeqcAXjXysuRF7AfWWSARAKj+CJyxOmNCvc/XphSWhT3Osf2seYQqHg== 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 (24/08/08 04:37), Matthew Wilcox wrote: [..] > > I don't know if it's _your_ problem. It's _our_ problem. The arguments > for (at least attempting) to shrink struct page seem quite compelling. > We have a plan for most of the users of struct page, in greater or > lesser detail. I don't think we have a plan for zsmalloc. Or at least > if there is a plan, I don't know what it is. Got you, thanks. And sorry for a very delayed reply. > > > Do you allocate a per-page struct zpdesc, and have each one pointing > > > to a zspage? > > > > I'm not very knowledgeable when it comes to memdesc, excuse my > > ignorance, and please feel free to educate me. > > I've written about it here: > https://kernelnewbies.org/MatthewWilcox/Memdescs > https://kernelnewbies.org/MatthewWilcox/FolioAlloc > https://kernelnewbies.org/MatthewWilcox/Memdescs/Path Thanks a lot! > > So I guess if we have something > > > > struct zspage { > > .. > > struct zpdesc *first_desc; > > .. > > } > > > > and we "chain" zpdesc-s to form a zspage, and make each of them point to > > a corresponding struct page (memdesc -> *page), then it'll resemble current > > zsmalloc and should work for everyone? I also assume for zspdesc-s zsmalloc > > will need to maintain a dedicated kmem_cache? > > Right, we could do that. Each memdesc has to be a multiple of 16 bytes, > sp we'd be doing something like allocating 32 bytes for each page. > Is there really 32 bytes of information that we want to store for > each page? Or could we store all of the information in (a somewhat > larger) zspage? Assuming we allocate 3 pages per zspage, if we allocate > an extra 64 bytes in the zspage, we've saved 32 bytes per zspage. I certainly like (and appreciate) the approach that saves us some bytes here and there. zsmalloc page can consist of 1 to up to CONFIG_ZSMALLOC_CHAIN_SIZE (max 16) physical pages. I'm trying to understand (in pseudo-C code) what does a "somewhat larger zspage" mean. A fixed size array (given that we know the max number of physical pages) per-zspage?