From: Yunsheng Lin <linyunsheng@huawei.com>
To: <davem@davemloft.net>, <kuba@kernel.org>, <pabeni@redhat.com>
Cc: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Yunsheng Lin <linyunsheng@huawei.com>,
Alexander Duyck <alexander.duyck@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>
Subject: [PATCH net-next v2 05/15] mm: page_frag: use initial zero offset for page_frag_alloc_align()
Date: Mon, 15 Apr 2024 21:19:30 +0800 [thread overview]
Message-ID: <20240415131941.51153-6-linyunsheng@huawei.com> (raw)
In-Reply-To: <20240415131941.51153-1-linyunsheng@huawei.com>
We are above to use page_frag_alloc_*() API to not just
allocate memory for skb->data, but also use them to do
the memory allocation for skb frag too. Currently the
implementation of page_frag in mm subsystem is running
the offset as a countdown rather than count-up value,
there may have several advantages to that as mentioned
in [1], but it may have some disadvantages, for example,
it may disable skb frag coaleasing and more correct cache
prefetching
We have a trade-off to make in order to have a unified
implementation and API for page_frag, so use a initial zero
offset in this patch, and the following patch will try to
make some optimization to aovid the disadvantages as much
as possible.
1. https://lore.kernel.org/all/f4abe71b3439b39d17a6fb2d410180f367cadf5c.camel@gmail.com/
CC: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
---
mm/page_frag_cache.c | 31 ++++++++++++++-----------------
1 file changed, 14 insertions(+), 17 deletions(-)
diff --git a/mm/page_frag_cache.c b/mm/page_frag_cache.c
index 64993b5d1243..dc864ee09536 100644
--- a/mm/page_frag_cache.c
+++ b/mm/page_frag_cache.c
@@ -65,9 +65,8 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc,
unsigned int fragsz, gfp_t gfp_mask,
unsigned int align_mask)
{
- unsigned int size = PAGE_SIZE;
+ unsigned int size, offset;
struct page *page;
- int offset;
if (unlikely(!nc->va)) {
refill:
@@ -75,10 +74,6 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc,
if (!page)
return NULL;
-#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- /* if size can vary use size else just use PAGE_SIZE */
- size = nc->size;
-#endif
/* Even if we own the page, we do not use atomic_set().
* This would break get_page_unless_zero() users.
*/
@@ -87,11 +82,18 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc,
/* reset page count bias and offset to start of new frag */
nc->pfmemalloc = page_is_pfmemalloc(page);
nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
- nc->offset = size;
+ nc->offset = 0;
}
- offset = 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 = nc->size;
+#else
+ size = PAGE_SIZE;
+#endif
+
+ offset = ALIGN(nc->offset, -align_mask);
+ if (unlikely(offset + fragsz > size)) {
page = virt_to_page(nc->va);
if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
@@ -102,17 +104,13 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc,
goto refill;
}
-#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- /* if size can vary use size else just use PAGE_SIZE */
- size = nc->size;
-#endif
/* OK, page count is 0, we can safely set it */
set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
/* reset page count bias and offset to start of new frag */
nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
- offset = size - fragsz;
- if (unlikely(offset < 0)) {
+ offset = 0;
+ if (unlikely(fragsz > size)) {
/*
* The caller is trying to allocate a fragment
* with fragsz > PAGE_SIZE but the cache isn't big
@@ -127,8 +125,7 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc,
}
nc->pagecnt_bias--;
- offset &= align_mask;
- nc->offset = offset;
+ nc->offset = offset + fragsz;
return nc->va + offset;
}
--
2.33.0
next prev parent reply other threads:[~2024-04-15 13:22 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240415131941.51153-1-linyunsheng@huawei.com>
2024-04-15 13:19 ` [PATCH net-next v2 01/15] mm: page_frag: add a test module for page_frag Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 03/15] mm: page_frag: use free_unref_page() to free page fragment Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 04/15] mm: move the page fragment allocator from page_alloc into its own file Yunsheng Lin
2024-04-15 13:19 ` Yunsheng Lin [this message]
2024-04-15 23:55 ` [PATCH net-next v2 05/15] mm: page_frag: use initial zero offset for page_frag_alloc_align() Alexander H Duyck
2024-04-16 13:11 ` Yunsheng Lin
2024-04-16 15:51 ` Alexander H Duyck
2024-04-17 13:17 ` Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 06/15] mm: page_frag: change page_frag_alloc_* API to accept align param Yunsheng Lin
2024-04-16 16:08 ` Alexander Duyck
2024-04-17 13:18 ` Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 07/15] mm: page_frag: add '_va' suffix to page_frag API Yunsheng Lin
2024-04-16 16:12 ` Alexander H Duyck
2024-04-17 13:18 ` Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 08/15] mm: page_frag: add two inline helper for " Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 09/15] mm: page_frag: reuse MSB of 'size' field for pfmemalloc Yunsheng Lin
2024-04-16 16:22 ` Alexander H Duyck
2024-04-17 13:19 ` Yunsheng Lin
2024-04-17 15:11 ` Alexander H Duyck
2024-04-18 9:39 ` Yunsheng Lin
2024-04-26 9:38 ` Yunsheng Lin
2024-04-29 14:49 ` Alexander Duyck
2024-04-30 12:05 ` Yunsheng Lin
2024-04-30 14:54 ` Alexander Duyck
2024-05-06 12:33 ` Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 10/15] mm: page_frag: reuse existing bit field of 'va' for pagecnt_bias Yunsheng Lin
2024-04-16 16:33 ` Alexander H Duyck
2024-04-17 13:23 ` Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 12/15] mm: page_frag: introduce prepare/commit API for page_frag Yunsheng Lin
2024-04-15 13:19 ` [PATCH net-next v2 14/15] mm: page_frag: update documentation " Yunsheng Lin
2024-04-16 6:13 ` Bagas Sanjaya
2024-04-16 13:11 ` Yunsheng Lin
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