From nobody Thu Nov 14 05:16:08 2024 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 CBE5EC4167B for ; Fri, 1 Dec 2023 12:02:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378700AbjLAMCX (ORCPT ); Fri, 1 Dec 2023 07:02:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378688AbjLAMCQ (ORCPT ); Fri, 1 Dec 2023 07:02:16 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2529A170E; Fri, 1 Dec 2023 04:02:22 -0800 (PST) Received: from dggpemm500005.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4ShWqx2WS9zWhx4; Fri, 1 Dec 2023 20:01:33 +0800 (CST) Received: from localhost.localdomain (10.69.192.56) 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; Fri, 1 Dec 2023 20:02:20 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Alexander Duyck , Andrew Morton , Subject: [PATCH RFC 3/6] mm/page_alloc: use initial zero offset for page_frag_alloc_align() Date: Fri, 1 Dec 2023 20:02:04 +0800 Message-ID: <20231201120208.15080-4-linyunsheng@huawei.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20231201120208.15080-1-linyunsheng@huawei.com> References: <20231201120208.15080-1-linyunsheng@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.69.192.56] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) 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 Content-Type: text/plain; charset="utf-8" The next patch is above to use page_frag_alloc_align() to replace vhost_net_page_frag_refill(), the main difference between those two frag page implementations is whether we use a initial zero offset or not. It seems more nature to use a initial zero offset, as it may enable more correct cache prefetching and skb frag coalescing in the networking, so change it to use initial zero offset. Signed-off-by: Yunsheng Lin CC: Alexander Duyck --- mm/page_alloc.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1f0b36dd81b5..083e0c38fb62 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4720,7 +4720,7 @@ void *page_frag_alloc_align(struct page_frag_cache *n= c, unsigned int fragsz, gfp_t gfp_mask, unsigned int align) { - unsigned int size =3D PAGE_SIZE; + unsigned int size; struct page *page; int offset; =20 @@ -4732,10 +4732,6 @@ void *page_frag_alloc_align(struct page_frag_cache *= nc, if (!page) return NULL; =20 -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - /* if size can vary use size else just use PAGE_SIZE */ - size =3D nc->size; -#endif /* Even if we own the page, we do not use atomic_set(). * This would break get_page_unless_zero() users. */ @@ -4744,11 +4740,18 @@ void *page_frag_alloc_align(struct page_frag_cache = *nc, /* reset page count bias and offset to start of new frag */ nc->pfmemalloc =3D page_is_pfmemalloc(page); nc->pagecnt_bias =3D PAGE_FRAG_CACHE_MAX_SIZE + 1; - nc->offset =3D size; + nc->offset =3D 0; } =20 - offset =3D nc->offset - fragsz; - if (unlikely(offset < 0)) { +#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) + /* if size can vary use size else just use PAGE_SIZE */ + size =3D nc->size; +#else + size =3D PAGE_SIZE; +#endif + + offset =3D ALIGN(nc->offset, align); + if (unlikely(offset + fragsz > size)) { page =3D virt_to_page(nc->va); =20 if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) @@ -4759,17 +4762,13 @@ void *page_frag_alloc_align(struct page_frag_cache = *nc, goto refill; } =20 -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - /* if size can vary use size else just use PAGE_SIZE */ - size =3D nc->size; -#endif /* OK, page count is 0, we can safely set it */ set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1); =20 /* reset page count bias and offset to start of new frag */ nc->pagecnt_bias =3D PAGE_FRAG_CACHE_MAX_SIZE + 1; - offset =3D size - fragsz; - if (unlikely(offset < 0)) { + offset =3D 0; + if (unlikely(fragsz > size)) { /* * The caller is trying to allocate a fragment * with fragsz > PAGE_SIZE but the cache isn't big @@ -4784,8 +4783,7 @@ void *page_frag_alloc_align(struct page_frag_cache *n= c, } =20 nc->pagecnt_bias--; - offset &=3D -align; - nc->offset =3D offset; + nc->offset =3D offset + fragsz; =20 return nc->va + offset; } --=20 2.33.0