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Wed, 20 Jul 2022 17:41:59 -0700 (PDT) Date: Wed, 20 Jul 2022 17:41:58 -0700 (PDT) From: David Rientjes To: Zach O'Keefe cc: Andrew Morton , linux-mm@kvack.org, Hugh Dickins , Yang Shi , Miaohe Lin Subject: Re: [PATCH mm-unstable 1/4] mm/khugepaged: Use minimal bits to store num page < HPAGE_PMD_NR In-Reply-To: <20220720140603.1958773-2-zokeefe@google.com> Message-ID: <3ace9ceb-fd57-f356-235f-dae943d34f1d@google.com> References: <20220720140603.1958773-1-zokeefe@google.com> <20220720140603.1958773-2-zokeefe@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VXUzo7J5; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf12.hostedemail.com: domain of rientjes@google.com designates 209.85.215.178 as permitted sender) smtp.mailfrom=rientjes@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658364121; 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=lWjlVYd787fmqHst8sN//3SyrxTT6jpMqefEvZnqbiQ=; b=oBrOLmLrKch0N0jw3Yt53CsSBmfvv6Uv2wWYWGqYpxSRHksTtTpiRoGvseY8UYQoXUqGVb FS8e0CNP2cI1FgnrRVL1DsKlI8REUkybBxIB+lJKi13PGSQ7r8HoF1M1x2vrK6jtX9f3HN 1MPFB3gPr+VV5XUnbCi5GFQPmzZ1Dpo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658364121; a=rsa-sha256; cv=none; b=NdTMcdaE3bCbFEA/S9MP4pghy/pDxZS444zROypQY8kQfYyjS7OkARShm/Og/TYo1+j9q+ 6B9FG/cWLYQEygpWsqNHWnNdbN/enX8qI2R57rpvgsD8IufAVLjqg96bKVX1g3kEwVEU/3 UtT/cd45fI761dOU7kXtgXGsF3lNo74= X-Rspamd-Queue-Id: 2E7FA40098 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VXUzo7J5; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf12.hostedemail.com: domain of rientjes@google.com designates 209.85.215.178 as permitted sender) smtp.mailfrom=rientjes@google.com X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: k8yu9xpj76ees8taw18iyhhsyaz9eski X-HE-Tag: 1658364121-625600 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: On Wed, 20 Jul 2022, Zach O'Keefe wrote: > Minimally, node_load[] entries just need to be able to hold the maximum > value of HPAGE_PMD_NR, which is compile-time defined per-arch based on > PMD_SHIFT and PAGE_SHIFT. node_load[] is only written either via memset(), > or with via post-increment. struct collapse_control may be allocated > via kmalloc() in other collapse contexts, and MAX_NUMNODES may be > arbitrarily large. #define the underlying type of node_load[] based off > HPAGE_PMD_NR to avoid excessive memory allocated for this struct. > > Fixes: 3b07f3bb225a ("mm/khugepaged: add struct collapse_control") > Link: https://lore.kernel.org/linux-mm/Ys2CeIm%2FQmQwWh9a@google.com/ > Signed-off-by: Zach O'Keefe Acked-by: David Rientjes