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[54.240.9.35]) by mx.google.com with ESMTPS id b11si102161qvo.145.2019.04.04.08.46.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 04 Apr 2019 08:46:31 -0700 (PDT) Received-SPF: pass (google.com: domain of 01000169e907b8a0-2dbaab3f-18ad-4744-a81a-78809e2b7756-000000@amazonses.com designates 54.240.9.35 as permitted sender) client-ip=54.240.9.35; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw header.b="ZWOn1Mc/"; spf=pass (google.com: domain of 01000169e907b8a0-2dbaab3f-18ad-4744-a81a-78809e2b7756-000000@amazonses.com designates 54.240.9.35 as permitted sender) smtp.mailfrom=01000169e907b8a0-2dbaab3f-18ad-4744-a81a-78809e2b7756-000000@amazonses.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw; d=amazonses.com; t=1554392791; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=X/2BCjBLOwDcCBYuqS+EKFW7PX1QL8vk7+x2K01CwMI=; b=ZWOn1Mc/6/Z6wYKOt+kb2vZGIZ2iEyJ6G8RhqF5UjGurHdo7LenW790CvTeKwXqp ffbQj3A2xpA88fJD8sVpYGoZRwnuJvSLw6hh3FnOb9nIEY9WKY74uZrvxvIzQGkwFu6 drKobnYvkMnqw2qFeDTht5FgRvoE0Us5o+pBRNvA= Date: Thu, 4 Apr 2019 15:46:31 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Al Viro cc: "Tobin C. Harding" , Andrew Morton , Roman Gushchin , Alexander Viro , Christoph Hellwig , Pekka Enberg , David Rientjes , Joonsoo Kim , Matthew Wilcox , Miklos Szeredi , Andreas Dilger , Waiman Long , Tycho Andersen , Theodore Ts'o , Andi Kleen , David Chinner , Nick Piggin , Rik van Riel , Hugh Dickins , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [RFC PATCH v2 14/14] dcache: Implement object migration In-Reply-To: <20190403182454.GU2217@ZenIV.linux.org.uk> Message-ID: <01000169e907b8a0-2dbaab3f-18ad-4744-a81a-78809e2b7756-000000@email.amazonses.com> References: <20190403042127.18755-1-tobin@kernel.org> <20190403042127.18755-15-tobin@kernel.org> <20190403170811.GR2217@ZenIV.linux.org.uk> <01000169e458534a-3c6a5d6f-3054-4c64-b5f9-7f46c811eeac-000000@email.amazonses.com> <20190403182454.GU2217@ZenIV.linux.org.uk> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.04.04-54.240.9.35 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES 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, 3 Apr 2019, Al Viro wrote: > > This is an RFC and we want to know how to do this right. > > If by "how to do it right" you mean "expedit kicking out something with > non-zero refcount" - there's no way to do that. Nothing even remotely > sane. Sure we know that. > If you mean "kick out everything in this page with zero refcount" - that > can be done (see further in the thread). Ok that would already be progress. If we can use this to liberate some slab pages with just a few dentry object then it may be worthwhile. > Look, dentries and inodes are really, really not relocatable. If they > can be evicted by memory pressure - sure, we can do that for a given > set (e.g. "everything in that page"). But that's it - if memory > pressure would _not_ get rid of that one, there's nothing to be done. > Again, all VM can do is to simulate shrinker hitting hard on given > bunch (rather than buggering the entire cache). If filesystem (or > something in VFS) says "it's busy", it bloody well _is_ busy and > won't be going away until it ceases to be such. Right. Thats why the patch attempted to check for these things to avoid touching such objects.