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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id o32si23637462pld.190.2019.04.25.04.34.01 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 25 Apr 2019 04:34:01 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=AzHNBn3p; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=2P/OrI6qmGjUCFCbm+VB2UcrjfJxvO5JKLdQJTO3M7w=; b=AzHNBn3peLU6Lo27trPd6sx3t 3E8gWwtce0okQhV+//69KaJ+mcOtBJb1D8fHcMxa4RWb4/sbSL2TLg6wt7pxkQXUzZbZpCI2PADBo k/3PaEKNpyWKqsHMVDo5y06JNeS6OAHRlQ99TZ9gt4LXXVakOwzOCYRt8DxB++uTa/Oziwfo22+9u DfuWoFh3KIAgwHURpPHv1NbZaalK5Rsbhtqp8KqMypqVLz3aCRjSVeXNHcRKw1P+aRkzH52Gc4+2N WLu6Ns80arNv+sJrHdidazBEg4Jzj4jWcTophB6LzkAGu9wvSeB9bITNBNRcyuW4S/qVzAMHlTRDC YC0Qfzefw==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJcdb-0000Pj-6e; Thu, 25 Apr 2019 11:33:59 +0000 Date: Thu, 25 Apr 2019 04:33:59 -0700 From: Matthew Wilcox To: Vlastimil Babka Cc: lsf-pc@lists.linux-foundation.org, Linux-FSDevel , linux-mm , linux-block@vger.kernel.org, Michal Hocko , Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim , Ming Lei , linux-xfs@vger.kernel.org, Christoph Hellwig , Dave Chinner , "Darrick J . Wong" Subject: Re: [LSF/MM TOPIC] guarantee natural alignment for kmalloc()? Message-ID: <20190425113358.GI19031@bombadil.infradead.org> References: <790b68b7-3689-0ff6-08ae-936728bc6458@suse.cz> <20190411132819.GB22763@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190411132819.GB22763@bombadil.infradead.org> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Thu, Apr 11, 2019 at 06:28:19AM -0700, Matthew Wilcox wrote: > On Thu, Apr 11, 2019 at 02:52:08PM +0200, Vlastimil Babka wrote: > > In the session I hope to resolve the question whether this is indeed the > > right thing to do for all kmalloc() users, without an explicit alignment > > requests, and if it's worth the potentially worse > > performance/fragmentation it would impose on a hypothetical new slab > > implementation for which it wouldn't be optimal to split power-of-two > > sized pages into power-of-two-sized objects (or whether there are any > > other downsides). > > I think this is exactly the kind of discussion that LSFMM is for! It's > really a whole-system question; is Linux better-off having the flexibility > for allocators to return non-power-of-two aligned memory, or allowing > consumers of the kmalloc API to assume that "sufficiently large" memory > is naturally aligned. This has been scheduled for only the MM track. I think at least the filesystem people should be involved in this discussion since it's for their benefit. Do we have an lsf-discuss mailing list this year? Might be good to coordinate arrivals / departures for taxi sharing purposes.