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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 9AB8FC432C3 for ; Sat, 16 Nov 2019 11:36:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71861206D5 for ; Sat, 16 Nov 2019 11:36:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573904200; bh=TAMJQl+wOvZO1A1YRRxHSlQrHSkZpu1YkEi89X3QiYE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=aVEP5Gk9XRunpjTul025UtjakE+YfeJE9RtDNrr3WjYCgXvydaZWrJGusZQwVxBAu ryHYVl8seolwv3SnGm+wcSJsKtIeqC8QYPqR+fgNJ2eO+ksstARxQUaZupgcaxoQL0 79yNWARTT7hr+gSmw5jb5MCXlkbe2VNcXzx7EhwU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727505AbfKPLgj (ORCPT ); Sat, 16 Nov 2019 06:36:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:48672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726794AbfKPLgj (ORCPT ); Sat, 16 Nov 2019 06:36:39 -0500 Received: from localhost.localdomain (unknown [77.139.212.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DDF4520723; Sat, 16 Nov 2019 11:36:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573904198; bh=TAMJQl+wOvZO1A1YRRxHSlQrHSkZpu1YkEi89X3QiYE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mm+WZqQR5vkVZLjt3VwWAJI3ZI5z3MFA63Or3Oq5++b3qvktqoMVzMheNaKOf/1Jj 2+a6Fd6iEjzIBZQRShsLECsVNk1F3n/rQtmZYqx2elRvYxG2OOrpyY9914VaJxu5eo ZXS5R6HZ+NdTKZ0T6REgUVuqaKWXAHzDwW/jKTG4= Date: Sat, 16 Nov 2019 13:36:30 +0200 From: Lorenzo Bianconi To: Jesper Dangaard Brouer Cc: netdev@vger.kernel.org, davem@davemloft.net, ilias.apalodimas@linaro.org, lorenzo.bianconi@redhat.com, mcroce@redhat.com Subject: Re: [PATCH v3 net-next 2/3] net: page_pool: add the possibility to sync DMA memory for device Message-ID: <20191116113630.GB20820@localhost.localdomain> References: <1e177bb63c858acdf5aeac9198c2815448d37820.1573844190.git.lorenzo@kernel.org> <20191116122017.78e29e27@carbon> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="St7VIuEGZ6dlpu13" Content-Disposition: inline In-Reply-To: <20191116122017.78e29e27@carbon> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --St7VIuEGZ6dlpu13 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > On Fri, 15 Nov 2019 21:01:38 +0200 > Lorenzo Bianconi wrote: >=20 > > static bool __page_pool_recycle_into_ring(struct page_pool *pool, > > - struct page *page) > > + struct page *page, > > + unsigned int dma_sync_size) > > { > > int ret; > > /* BH protection not needed if current is serving softirq */ > > @@ -264,6 +285,9 @@ static bool __page_pool_recycle_into_ring(struct pa= ge_pool *pool, > > else > > ret =3D ptr_ring_produce_bh(&pool->ring, page); > > =20 > > + if (ret =3D=3D 0 && (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)) > > + page_pool_dma_sync_for_device(pool, page, dma_sync_size); > > + > > return (ret =3D=3D 0) ? true : false; > > } >=20 >=20 > I do wonder if we should DMA-sync-for-device BEFORE putting page into > ptr_ring, as this is a channel between several concurrent CPUs. Hi Jesper, in this way we can end up syncing the DMA page even if it is unmapped in __page_pool_clean_page (e.g. if the ptr_ring is full), right? >=20 >=20 >=20 > > @@ -273,18 +297,22 @@ static bool __page_pool_recycle_into_ring(struct = page_pool *pool, > > * Caller must provide appropriate safe context. > > */ > > static bool __page_pool_recycle_direct(struct page *page, > > - struct page_pool *pool) > > + struct page_pool *pool, > > + unsigned int dma_sync_size) > > { > > if (unlikely(pool->alloc.count =3D=3D PP_ALLOC_CACHE_SIZE)) > > return false; > > =20 > > /* Caller MUST have verified/know (page_ref_count(page) =3D=3D 1) */ > > pool->alloc.cache[pool->alloc.count++] =3D page; > > + > > + if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > > + page_pool_dma_sync_for_device(pool, page, dma_sync_size); > > return true; > > } >=20 > We know __page_pool_recycle_direct() is concurrency safe, and only a > single (NAPI processing) CPU can enter. (So, the DMA-sync order is not > wrong here, but it could be swapped) do you mean move it before putting the page in the cache? pool->alloc.cache[pool->alloc.count++] =3D page; Regards, Lorenzo >=20 > --=20 > Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > LinkedIn: http://www.linkedin.com/in/brouer >=20 --St7VIuEGZ6dlpu13 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCXc/fOwAKCRA6cBh0uS2t rPHcAPwJGMNFddgcRh0SY73+cXkTj+sCELZQXz7OhIIQyTUiKAD/ZMGb9AINy9/R /9QIi2UqaMqLkgURmmFecVaZJG66DwE= =a8U9 -----END PGP SIGNATURE----- --St7VIuEGZ6dlpu13--