Abstract the memory type from the page_pool so we can later add support
for new memory types. Convert the page_pool to use the new netmem type
abstraction, rather than use struct page directly.
As of this patch the netmem type is a no-op abstraction: it's always a
struct page underneath. All the page pool internals are converted to
use struct netmem instead of struct page, and the page pool now exports
2 APIs:
1. The existing struct page API.
2. The new struct netmem API.
Keeping the existing API is transitional; we do not want to refactor all
the current drivers using the page pool at once.
The netmem abstraction is currently a no-op. The page_pool uses
page_to_netmem() to convert allocated pages to netmem, and uses
netmem_to_page() to convert the netmem back to pages to pass to mm APIs,
Follow up patches to this series add non-paged netmem support to the
page_pool. This change is factored out on its own to limit the code
churn to this 1 patch, for ease of code review.
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/20240628003253.1694510-6-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Each driver is responsible for syncing buffers written by HW for CPU
before accessing them. Almost each PP-enabled driver uses the same
pattern, which could be shorthanded into a static inline to make driver
code a little bit more compact.
Introduce a simple helper which performs DMA synchronization for the
size passed from the driver. It can be used even when the pool doesn't
manage DMA-syncs-for-device, just make sure the page has a correct DMA
address set via page_pool_set_dma_addr().
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
There are several functions taking pointers to data they don't modify.
This includes statistics fetching, page and page_pool parameters, etc.
Constify the pointers, so that call sites will be able to pass const
pointers as well.
No functional changes, no visible changes in functions sizes.
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
In order to address the issues encountered with commit 1effe8ca4e
("skbuff: fix coalescing for page_pool fragment recycling"), the
combination of the following condition was excluded from skb coalescing:
from->pp_recycle = 1
from->cloned = 1
to->pp_recycle = 1
However, with page pool environments, the aforementioned combination can
be quite common(ex. NetworkMananger may lead to the additional
packet_type being registered, thus the cloning). In scenarios with a
higher number of small packets, it can significantly affect the success
rate of coalescing. For example, considering packets of 256 bytes size,
our comparison of coalescing success rate is as follows:
Without page pool: 70%
With page pool: 13%
Consequently, this has an impact on performance:
Without page pool: 2.57 Gbits/sec
With page pool: 2.26 Gbits/sec
Therefore, it seems worthwhile to optimize this scenario and enable
coalescing of this particular combination. To achieve this, we need to
ensure the correct increment of the "from" SKB page's page pool
reference count (pp_ref_count).
Following this optimization, the success rate of coalescing measured in
our environment has improved as follows:
With page pool: 60%
This success rate is approaching the rate achieved without using page
pool, and the performance has also been improved:
With page pool: 2.52 Gbits/sec
Below is the performance comparison for small packets before and after
this optimization. We observe no impact to packets larger than 4K.
packet size before after improved
(bytes) (Gbits/sec) (Gbits/sec)
128 1.19 1.27 7.13%
256 2.26 2.52 11.75%
512 4.13 4.81 16.50%
1024 6.17 6.73 9.05%
2048 14.54 15.47 6.45%
4096 25.44 27.87 9.52%
Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
To support multiple users referencing the same fragment,
'pp_frag_count' is renamed to 'pp_ref_count', transitioning pp pages
from fragment management to reference count management after draining
based on the suggestion from [1].
The idea is that the concept of fragmenting exists before the page is
drained, and all related functions retain their current names.
However, once the page is drained, its management shifts to being
governed by 'pp_ref_count'. Therefore, all functions associated with
that lifecycle stage of a pp page are renamed.
[1]
http://lore.kernel.org/netdev/f71d9448-70c8-8793-dc9a-0eb48a570300@huawei.com
Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20231212044614.42733-2-liangchen.linux@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As more drivers begin to use the fragment API, update the
document about how to decide which API to use for the
driver author.
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
CC: Dima Tisnek <dimaqq@gmail.com>
Link: https://lore.kernel.org/r/20231020095952.11055-5-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently page pool supports the below use cases:
use case 1: allocate page without page splitting using
page_pool_alloc_pages() API if the driver knows
that the memory it need is always bigger than
half of the page allocated from page pool.
use case 2: allocate page frag with page splitting using
page_pool_alloc_frag() API if the driver knows
that the memory it need is always smaller than
or equal to the half of the page allocated from
page pool.
There is emerging use case [1] & [2] that is a mix of the
above two case: the driver doesn't know the size of memory it
need beforehand, so the driver may use something like below to
allocate memory with least memory utilization and performance
penalty:
if (size << 1 > max_size)
page = page_pool_alloc_pages();
else
page = page_pool_alloc_frag();
To avoid the driver doing something like above, add the
page_pool_alloc() API to support the above use case, and update
the true size of memory that is acctually allocated by updating
'*size' back to the driver in order to avoid exacerbating
truesize underestimate problem.
Rename page_pool_free() which is used in the destroy process to
__page_pool_destroy() to avoid confusion with the newly added
API.
1. https://lore.kernel.org/all/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/
2. https://lore.kernel.org/all/20230526054621.18371-3-liangchen.linux@gmail.com/
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://lore.kernel.org/r/20231020095952.11055-4-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently when page_pool_create() is called with
PP_FLAG_PAGE_FRAG flag, page_pool_alloc_pages() is only
allowed to be called under the below constraints:
1. page_pool_fragment_page() need to be called to setup
page->pp_frag_count immediately.
2. page_pool_defrag_page() often need to be called to drain
the page->pp_frag_count when there is no more user will
be holding on to that page.
Those constraints exist in order to support a page to be
split into multi fragments.
And those constraints have some overhead because of the
cache line dirtying/bouncing and atomic update.
Those constraints are unavoidable for case when we need a
page to be split into more than one fragment, but there is
also case that we want to avoid the above constraints and
their overhead when a page can't be split as it can only
hold a fragment as requested by user, depending on different
use cases:
use case 1: allocate page without page splitting.
use case 2: allocate page with page splitting.
use case 3: allocate page with or without page splitting
depending on the fragment size.
Currently page pool only provide page_pool_alloc_pages() and
page_pool_alloc_frag() API to enable the 1 & 2 separately,
so we can not use a combination of 1 & 2 to enable 3, it is
not possible yet because of the per page_pool flag
PP_FLAG_PAGE_FRAG.
So in order to allow allocating unsplit page without the
overhead of split page while still allow allocating split
page we need to remove the per page_pool flag in
page_pool_is_last_frag(), as best as I can think of, it seems
there are two methods as below:
1. Add per page flag/bit to indicate a page is split or
not, which means we might need to update that flag/bit
everytime the page is recycled, dirtying the cache line
of 'struct page' for use case 1.
2. Unify the page->pp_frag_count handling for both split and
unsplit page by assuming all pages in the page pool is split
into a big fragment initially.
As page pool already supports use case 1 without dirtying the
cache line of 'struct page' whenever a page is recyclable, we
need to support the above use case 3 with minimal overhead,
especially not adding any noticeable overhead for use case 1,
and we are already doing an optimization by not updating
pp_frag_count in page_pool_defrag_page() for the last fragment
user, this patch chooses to unify the pp_frag_count handling
to support the above use case 3.
There is no noticeable performance degradation and some
justification for unifying the frag_count handling with this
patch applied using a micro-benchmark testing in [1].
1. https://lore.kernel.org/all/bf2591f8-7b3c-4480-bb2c-31dc9da1d6ac@huawei.com/
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://lore.kernel.org/r/20231020095952.11055-2-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently page_pool_alloc_frag() is not supported in 32-bit
arch with 64-bit DMA because of the overlap issue between
pp_frag_count and dma_addr_upper in 'struct page' for those
arches, which seems to be quite common, see [1], which means
driver may need to handle it when using fragment API.
It is assumed that the combination of the above arch with an
address space >16TB does not exist, as all those arches have
64b equivalent, it seems logical to use the 64b version for a
system with a large address space. It is also assumed that dma
address is page aligned when we are dma mapping a page aligned
buffer, see [2].
That means we're storing 12 bits of 0 at the lower end for a
dma address, we can reuse those bits for the above arches to
support 32b+12b, which is 16TB of memory.
If we make a wrong assumption, a warning is emitted so that
user can report to us.
1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@huawei.com/
2. https://lore.kernel.org/all/20230818145145.4b357c89@kernel.org/
Tested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Guillaume Tucker <guillaume.tucker@collabora.com>
CC: Matthew Wilcox <willy@infradead.org>
CC: Linux-MM <linux-mm@kvack.org>
Link: https://lore.kernel.org/r/20231013064827.61135-2-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
In commit 82e896d992 ("docs: net: page_pool: use kdoc to avoid
duplicating the information") I shied away from using the DOC:
comments when moving to kdoc for documenting page_pool API,
because I wasn't sure how familiar people are with it.
Turns out there is already a DOC: comment for the intro, which
is the same in both places, modulo what looks like minor rewording.
Use the version from Documentation/ but keep the contents with
the code.
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://lore.kernel.org/r/20230807210051.1014580-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Split types and pure function declarations from page_pool.h
and add them in page_page/types.h, so that C sources can
include page_pool.h and headers should generally only include
page_pool/types.h as suggested by jakub.
Rename page_pool.h to page_pool/helpers.h to have both in
one place.
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://lore.kernel.org/r/20230804180529.2483231-2-aleksander.lobakin@intel.com
[Jakub: change microsoft/mana, fix kdoc paths in Documentation]
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
