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 2A8F5CF9C71 for ; Tue, 24 Sep 2024 23:11:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 86BD36B0099; Tue, 24 Sep 2024 19:11:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 81BFB6B009B; Tue, 24 Sep 2024 19:11:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6E30A6B009C; Tue, 24 Sep 2024 19:11:29 -0400 (EDT) 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 4C39C6B0099 for ; Tue, 24 Sep 2024 19:11:29 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id F37D3ABE2E for ; Tue, 24 Sep 2024 23:11:28 +0000 (UTC) X-FDA: 82601180256.08.B90302E Received: from mail-qv1-f46.google.com (mail-qv1-f46.google.com [209.85.219.46]) by imf21.hostedemail.com (Postfix) with ESMTP id 31D5C1C000D for ; Tue, 24 Sep 2024 23:11:27 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=S7wpj9DU; spf=pass (imf21.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.219.46 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727219367; 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=5rZRTN22GVeTXjjYCrCBFgvO2TrIVhxxPF4nOlAMLMU=; b=HOJZzqnT2y9FY2g6gOiBOlANySXzKTgrQdyd+RQGyGEdrFRJfq1XAzhew64B0XffyWpLsN bYSSlMFehI+anFOFofPrIPuP0Kg39JvWYw6vCwtV/u2xNZpuu7FPoqM+yX4WzffCyZh6fw vwor91lbP7WoohOAJbIQlRKN6sajMPc= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1727219367; a=rsa-sha256; cv=none; b=hDtxhsLwXXkbPecGC2DuEnbKKVuc6apRiqBjsCIpTkQSemwT277TZFHz8ZOPZss0Zi6i70 VVUNPMdBfeEA2kFDA1rn9DMJvJovgQv7Wx/y1ZqUov2M2M6az6itW2FZ8w+ro5GyPo3php qFlamVFKIMN8oXgXV3xCXm6IdQwlDng= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=S7wpj9DU; spf=pass (imf21.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.219.46 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com Received: by mail-qv1-f46.google.com with SMTP id 6a1803df08f44-6c34dd6c1b4so43178346d6.1 for ; Tue, 24 Sep 2024 16:11:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1727219486; x=1727824286; 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=5rZRTN22GVeTXjjYCrCBFgvO2TrIVhxxPF4nOlAMLMU=; b=S7wpj9DUuG9iApM5BBjtJ6E1BnoHMWGXKgccHongh/xL98p240yBazvwLSYwQAzZdj 6omqSVEeh7U//cc7BaNE3b7J++KYjzqoLVAX75p/qwoPtMtdeidDtpPWTRJP73NsMcCK ss1OukVy3lcjvTpvN4iHcFwhsW0ydZz7xYFEExMP5iyFlIAUyE+tCh6P76wRFf6p8swu +6+GJXeroNSqrpAmtw3hcx4AjNgxt9GpVTaYy95aXrnblVrxiS5CyJRd38hWJ51y+5Nz 3bMg9jPm3q3qeWdVxKTynmpxSmpFWqjzJsOCpP7f1SiECHFL6Od5J4b+VZndR3F5MEiR M+eg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727219486; x=1727824286; 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=5rZRTN22GVeTXjjYCrCBFgvO2TrIVhxxPF4nOlAMLMU=; b=NWn7VHbOSpiOayCIUH52Fv8v5biTFI5+YUkAHcz7Hnd5VpRGeMT9hLFP6Bf0rKA3nO YOnR2xu+IEXCEHgM2k9AVhvsTvMh42qp/9Vsp63tIuCaq3oBSC9Bt0Y9c41Et4QTDme4 x/f/V+ZNvfxDx4nVr8nSaTTXHA1XLFIzOGJ+k2Wuu3FrkL1moFcQzD12L+DPdT64Y7KQ ZMziDAf4NYlwTTw2G1dLh5fiqp7PzIogRUWA1nQlU1isgs1HyMfwgoAab5dTtGBG2AJG rvBB9ZWjaQjBGhUsPDj7onDfx7egzm9295WnhJWv+E6a8HMtRdpBOTx+hp4uWJn+uhyq 0OdA== X-Forwarded-Encrypted: i=1; AJvYcCWeb5gJUr9ksBqXcIq3tmh8k3/C7xPZ+qzM3KM3MZlQInWcCH0TSCSUCgpRR3/3kW8RS1i+AfzekA==@kvack.org X-Gm-Message-State: AOJu0Yw0Vepa6VzY0MIiTOrlF+W6sbFFGJ8bgHqGB/HRs68U2Z9Gx11X etATpX68IhXOH3YfvmkYMfMuz2EDYhQjSyzeO6xN5oaEj18Mwz0Wjp4XHPhlstEDBfC6pkN6MOB iyTYua2dEcrPTbO5pqBJnlS/8mAg= X-Google-Smtp-Source: AGHT+IG7su5eKcB2yug1KYtbxnX4YH3diGnU98W5SlFjFSNwN7XxF2mk3bDfxfvs7a1XD4o9ZwCRnz1dDKQm5dYUDJ0= X-Received: by 2002:a05:6214:2f0b:b0:6c3:69be:a3e with SMTP id 6a1803df08f44-6cb1de9a6a7mr9112386d6.43.1727219486252; Tue, 24 Sep 2024 16:11:26 -0700 (PDT) MIME-Version: 1.0 References: <20240924011709.7037-1-kanchana.p.sridhar@intel.com> <20240924011709.7037-7-kanchana.p.sridhar@intel.com> In-Reply-To: From: Nhat Pham Date: Tue, 24 Sep 2024 16:11:15 -0700 Message-ID: Subject: Re: [PATCH v7 6/8] mm: zswap: Support mTHP swapout in zswap_store(). To: Yosry Ahmed Cc: Kanchana P Sridhar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, chengming.zhou@linux.dev, usamaarif642@gmail.com, shakeel.butt@linux.dev, ryan.roberts@arm.com, ying.huang@intel.com, 21cnbao@gmail.com, akpm@linux-foundation.org, nanhai.zou@intel.com, wajdi.k.feghali@intel.com, vinodh.gopal@intel.com, joshua.hahnjy@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: iz3xfywopzx13n76zgyffkrihwfqmbbp X-Rspamd-Queue-Id: 31D5C1C000D X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1727219487-459555 X-HE-Meta: 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 1/0YV0TK I6GcEI1/UlLTurLd5VBIb65SgWADy6WMdtlOxJldc01E0/8fbxOKB52mAj4/mV/Lr/7jQwNRnwMxggyssKNRrsgFNerWu+IgHoyUO8Eo5KObQcmieFGfkpkqsYZsVmXxG3sjN7U60hles6/DqxMoBzt9mToo6oijjAjWI8P+GnljKVEyR/the7k204AEWnLcc2J2XL/bYid2qqdtRptbNWeW1X7jVDc178FbZzT7e36mQLVNH7plQtLjftuqE5ch1JCCqTlBnT5I65QsUOh2baXHY14KDVvPhojb5CBS8L9ZQHmEflc04LmLYC5qEJ5zbp4J4BwoC8sSxHfLjr0lrTHnxfBO8XdW2tJcfAKMcWOk6WGl/UzpgcYY3AK+pIF1ARJTilyIdEg/P8lKGOdSENVEIF692iyQ4cGuSLSRqvr1N3V/uz3V60zTgv7c3UBWpSaCP3f+ZeWn8xxc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.070291, 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 Tue, Sep 24, 2024 at 2:38=E2=80=AFPM Yosry Ahmed = wrote: > > > We can also do what we discussed before about double charging. The > pages that are being reclaimed are already charged, so technically we > don't need to charge them again. We can uncharge the difference > between compressed and uncompressed sizes after compression and call > it a day. This fixes the limit checking and the double charging in one > go. > I am a little bit nervous though about zswap uncharing the pages from > under reclaim, there are likely further accesses of the page memcg > after zswap. Maybe we can plumb the info back to reclaim or set a flag > on the page to avoid uncharging it when it's freed. Hmm this is just for memory usage charging, no? The problem here is the zswap usage (zswap.current), and its relation to the limit. One thing we can do is check the zswap usage against the limit for every subpage, but that's likely expensive...? With the new atomic counters Joshua is working on, we can check-and-charge at the same time, after we have compressed the whole large folio, like this: for (memcg =3D original_memcg; !mem_cgroup_is_root(memcg); memcg =3D parent_mem_cgroup(memcg)); old_usage =3D atomic_read(&memcg->zswap); do { new_usage =3D old_usage + size; if (new_usage > limit) { /* undo charging of descendants, then return false */ } } while (!atomic_try_cmpxchg(&memcg->zswap, old_usage, new_usage)) } But I don't know what we can do in the current design. I gave it some more thought, and even if we only check after we know the size, we can still potentially overshoot the limit :(