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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 95303E909BA for ; Tue, 17 Feb 2026 15:31:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=VibcOHxUnl/NZoQHJmtE8kefvpRGSAcGan9/Dpa0Or0=; b=q0I9sZeozmmn9T/a1BasOXklmr KvSYDapquDx2Yi4jD6hxEi3dhXznt2G1LD9jKV+5CSLr1D43H3JNodK3ppkNOaowrJ9AO10wUwt0E xNMrP0xSn/e37MgNL7N8wXdoUNZsx3rBvfshlhzc/4o3NpLgG9oJSqzMuZw2IL6eYHoCxPgVNPNKJ b8T7398iZ5A0oj1sqabKLmuLUgDAqjUvJkhZtAqQ+M6sOtkLjMFthDdJ9Ajb4CcU4HaanhSaPPPzB ywH+pYijodN0axtuESPdEq6hjPQsBsjeD4L0+TnEx7TEpRLCGxmB+QW6XKNbnMSWZuNWjV44DprWB FKGRiMSg==; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260217_073111_045822_C7CEDDDE X-CRM114-Status: GOOD ( 20.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/17/26 16:22, Matthew Wilcox wrote: > On Tue, Feb 17, 2026 at 08:20:26PM +0530, Dev Jain wrote: >> 2. Generic Linux MM enlightenment >> --------------------------------- >> We enlighten the Linux MM code to always hand out memory in the granularity > > Please don't use the term "enlighten". Tht's used to describe something > something or other with hypervisors. Come up with a new term or use one > that already exists. > >> File memory >> ----------- >> For a growing list of compliant file systems, large folios can already be >> stored in the page cache. There is even a mechanism, introduced to support >> filesystems with block sizes larger than the system page size, to set a >> hard-minimum size for folios on a per-address-space basis. This mechanism >> will be reused and extended to service the per-process page size requirements. >> >> One key reason that the 64K kernel currently consumes considerably more memory >> than the 4K kernel is that Linux systems often have lots of small >> configuration files which each require a page in the page cache. But these >> small files are (likely) only used by certain processes. So, we prefer to >> continue to cache those using a 4K page. >> Therefore, if a process with a larger page size maps a file whose pagecache >> contains smaller folios, we drop them and re-read the range with a folio >> order at least that of the process order. > > That's going to be messy. I don't have a good idea for solving this > problem, but the page cache really isn't set up to change minimum folio > order while the inode is in use. In a private conversation I also raised that some situations might make it impossible/hard to drop+re-read. One example I cam up with if a folio is simply long-term R/O pinned. But I am also not quite sure how mlock might interfere here. So yes, I think the page cache is likely the one of the most problematic/messy thing to handle. -- Cheers, David