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 2E80CC4167B for ; Thu, 30 Nov 2023 09:01:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231852AbjK3JAy (ORCPT ); Thu, 30 Nov 2023 04:00:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231782AbjK3JAu (ORCPT ); Thu, 30 Nov 2023 04:00:50 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E53A12C; Thu, 30 Nov 2023 01:00:55 -0800 (PST) Received: from dggpemm500005.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Sgqnj1l50zsR46; Thu, 30 Nov 2023 16:57:13 +0800 (CST) Received: from [10.69.30.204] (10.69.30.204) by dggpemm500005.china.huawei.com (7.185.36.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Thu, 30 Nov 2023 17:00:52 +0800 Subject: Re: [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2 To: Alexander H Duyck , David Howells , CC: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Willem de Bruijn , David Ahern , Matthew Wilcox , Jens Axboe , , , Jeroen de Borst , Catherine Sullivan , Shailend Chand , Felix Fietkau , John Crispin , Sean Wang , Mark Lee , Lorenzo Bianconi , Matthias Brugger , AngeloGioacchino Del Regno , Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Andrew Morton , , , References: <20230524153311.3625329-1-dhowells@redhat.com> <20230524153311.3625329-4-dhowells@redhat.com> <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com> From: Yunsheng Lin Message-ID: Date: Thu, 30 Nov 2023 17:00:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.69.30.204] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/5/27 23:54, Alexander H Duyck wrote: > On Wed, 2023-05-24 at 16:33 +0100, David Howells wrote: >> Make the page_frag_cache allocator's alignment parameter a power of 2 >> rather than a mask and give a warning if it isn't. >> >> This means that it's consistent with {napi,netdec}_alloc_frag_align() and >> allows __{napi,netdev}_alloc_frag_align() to be removed. I am trying to rmove the page frag implemetation in vhost_net_page_frag_refill() by using page_frag_alloc_align(), and I ended up having a simiar patch as this one. >> > > This goes against the original intention of these functions. One of the > reasons why this is being used is because when somebody enables > something like 2K jumbo frames they don't necessarily want to have to > allocate 4K SLABs. Instead they can just add a bit of overhead and get > almost twice the utilization out of an order 3 page. > > The requirement should only be cache alignment, not power of 2 > alignment. This isn't meant to be a slab allocator. We are just > sectioning up pages to handle mixed workloads. In the case of > networking we can end up getting everything from 60B packets, to 1514B > in the standard cases. That was why we started sectioning up pages in > the first place so putting a power of 2 requirement on it doens't fit > our use case at all and is what we were trying to get away from with > the SLAB allocators. It seems that is_power_of_2() checking in this patch does not excluding the non-align case if we are passing 'align' being 1, which means we still can support the 'everything from 60B packets, to 1514B' case. > > . >