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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 244C6C7618E for ; Fri, 21 Apr 2023 12:25:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230310AbjDUMZh (ORCPT ); Fri, 21 Apr 2023 08:25:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229632AbjDUMZf (ORCPT ); Fri, 21 Apr 2023 08:25:35 -0400 Received: from outbound-smtp51.blacknight.com (outbound-smtp51.blacknight.com [46.22.136.235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 186F28A53 for ; Fri, 21 Apr 2023 05:25:11 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp51.blacknight.com (Postfix) with ESMTPS id A4E78FACCD for ; Fri, 21 Apr 2023 13:25:09 +0100 (IST) Received: (qmail 25223 invoked from network); 21 Apr 2023 12:25:09 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.21.103]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 21 Apr 2023 12:25:09 -0000 Date: Fri, 21 Apr 2023 13:25:04 +0100 From: Mel Gorman To: Johannes Weiner Cc: linux-mm@kvack.org, Kaiyang Zhao , Vlastimil Babka , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [RFC PATCH 01/26] block: bdev: blockdev page cache is movable Message-ID: <20230421122504.pq76pj6hka2xdbpu@techsingularity.net> References: <20230418191313.268131-1-hannes@cmpxchg.org> <20230418191313.268131-2-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20230418191313.268131-2-hannes@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 18, 2023 at 03:12:48PM -0400, Johannes Weiner wrote: > While inspecting page blocks for the type of pages in them, I noticed > a large number of blockdev cache in unmovable blocks. However, these > pages are actually on the LRU, and their mapping has a .migrate_folio > callback; they can be reclaimed and compacted as necessary. > > Put them into movable blocks, so they don't cause pollution, and > subsequent proliferation, of unmovable blocks. > > Signed-off-by: Johannes Weiner Deserves to be split out and needs careful treatment. I don't recall exactly but I believe I encountered a problem with these allocations in the very distant past. Some of the allocations were movable and others weren't or had very long lifetimes. Something like being superblock-related or directory inodes being pinned for very long lengths of time. This is a *long* time ago and the picture almost certainly has changed but it's very possible that a high percentage, but not 100% of these allocations are not movable in practice. -- Mel Gorman SUSE Labs