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 CE470EB64D7 for ; Fri, 16 Jun 2023 15:29:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345994AbjFPP32 (ORCPT ); Fri, 16 Jun 2023 11:29:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345860AbjFPP30 (ORCPT ); Fri, 16 Jun 2023 11:29:26 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA7FB270B for ; Fri, 16 Jun 2023 08:28:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1686929322; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=maoLH1+iFdOHtUfb3uVlDmFpd4ojetev/CDoWNYqeqE=; b=cgNzMa7QiOpf+pFf4w28NVWxhDF7oTvZBjXdRekbIVbI9MQC2BiGnTyhdgS8QwsGrPeryh gkDO4JEOzPzsGmlDffQLrN+VdBPIvdFa6GH7T1qt5/0zt/HwQ/IFtYqt83l360a+HuI+Rd pEkeg6OY5a43X9xNtwy1UELsvVSaBpk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-277-VwVwMy6RNq2uvUCKs61D4w-1; Fri, 16 Jun 2023 11:28:36 -0400 X-MC-Unique: VwVwMy6RNq2uvUCKs61D4w-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A4AFF85A58A; Fri, 16 Jun 2023 15:28:35 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id C62E748FB01; Fri, 16 Jun 2023 15:28:30 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com> References: <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com> <20230524153311.3625329-1-dhowells@redhat.com> <20230524153311.3625329-4-dhowells@redhat.com> To: Alexander H Duyck Cc: dhowells@redhat.com, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Willem de Bruijn , David Ahern , Matthew Wilcox , Jens Axboe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, 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 , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-nvme@lists.infradead.org Subject: Re: [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <617058.1686929309.1@warthog.procyon.org.uk> Date: Fri, 16 Jun 2023 16:28:29 +0100 Message-ID: <617059.1686929309@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alexander H Duyck wrote: > The requirement should only be cache alignment, not power of 2 > alignment. Sure, but, upstream, page_frag_alloc_align() allows the specification of an alignment and applies that alignment by: offset &= align_mask; which doesn't really make sense unless the alignment boils down to being a power of two. Now, it might make sense to kill off the align_mask parameter and just go with SMP_CACHE_BYTES (which will be a power of two). Note, though, that most users seem to use an align_mask of ~0u which feels a bit dodgy (it's not an unsigned long), but is probably fine. David