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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6657EC2BA19 for ; Tue, 14 Apr 2020 07:23:19 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 28A6D20774 for ; Tue, 14 Apr 2020 07:23:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="KMpTmVaG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 28A6D20774 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1c3t2Job0pgIS4x3LBtd+F7otmy1pXLQqO6r+Nf98xc=; b=KMpTmVaGKb309R 2Ti52ambGHeAdqHd9GQNxnv2IBtsssdH5MHZWflB0F7G5GieFyZSEUnZmIPcczRLLWwiQ9Ascrso5 05V8KBv+9mDpTEhfJXyuCDInOd9B3Ri6SiKzvN9wduhPDd/kl50132XXINfT7buZxS2zX+3WmIkFB VU1H1KTVUeAta0PGeHSIMD+B4/fME029Tr/4JH1qyaru3FVQ8DwdRcW55s+ELnboCGBM7qu335JKO 7HOrt0o4uEQYrnJWDs+cqzn9VRULslIhoI/zG3AxzCfFPucHZtuuanv6tQ+eQ7cwuez8b8pH/NrYy aZyoSZiObyoeT1qDATvg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOFug-0002EG-9T; Tue, 14 Apr 2020 07:23:18 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOFue-0002Dm-Hj; Tue, 14 Apr 2020 07:23:16 +0000 Date: Tue, 14 Apr 2020 00:23:16 -0700 From: Christoph Hellwig To: Nicholas Piggin Subject: Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings Message-ID: <20200414072316.GA5503@infradead.org> References: <20200413125303.423864-1-npiggin@gmail.com> <20200413125303.423864-5-npiggin@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200413125303.423864-5-npiggin@gmail.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Will Deacon , Catalin Marinas , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Apr 13, 2020 at 10:53:03PM +1000, Nicholas Piggin wrote: > For platforms that define HAVE_ARCH_HUGE_VMAP and support PMD vmap mappings, > have vmalloc attempt to allocate PMD-sized pages first, before falling back > to small pages. Allocations which use something other than PAGE_KERNEL > protections are not permitted to use huge pages yet, not all callers expect > this (e.g., module allocations vs strict module rwx). > > This gives a 6x reduction in dTLB misses for a `git diff` (of linux), from > 45600 to 6500 and a 2.2% reduction in cycles on a 2-node POWER9. > > This can result in more internal fragmentation and memory overhead for a > given allocation. It can also cause greater NUMA unbalance on hashdist > allocations. > > There may be other callers that expect small pages under vmalloc but use > PAGE_KERNEL, I'm not sure if it's feasible to catch them all. An > alternative would be a new function or flag which enables large mappings, > and use that in callers. Why do we even use vmalloc in this case rather than just doing a huge page allocation? What callers are you intersted in? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel