linux-toradex.git/mm/page_frag_cache.c, branch v6.19

mm/page_alloc: export free_frozen_pages() instead of free_unref_page()

2025-01-14T06:40:31+00:00

We already have the concept of "frozen pages" (eg page_ref_freeze()), so
let's not complicate things by also having the concept of "unref pages".

Link: https://lkml.kernel.org/r/20241125210149.2976098-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: David Hildenbrand 
Reviewed-by: William Kucharski 
Reviewed-by: Miaohe Lin 
Reviewed-by: Muchun Song 
Reviewed-by: Zi Yan 
Reviewed-by: Vlastimil Babka 
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Mel Gorman 
Signed-off-by: Andrew Morton

mm: page_frag: use __alloc_pages() to replace alloc_pages_node()

2024-11-11T18:56:27+00:00

It seems there is about 24Bytes binary size increase for
__page_frag_cache_refill() after refactoring in arm64 system
with 64K PAGE_SIZE. By doing the gdb disassembling, It seems
we can have more than 100Bytes decrease for the binary size
by using __alloc_pages() to replace alloc_pages_node(), as
there seems to be some unnecessary checking for nid being
NUMA_NO_NODE, especially when page_frag is part of the mm
system.

CC: Andrew Morton 
CC: Linux-MM 
Signed-off-by: Yunsheng Lin 
Reviewed-by: Alexander Duyck 
Link: https://patch.msgid.link/20241028115343.3405838-8-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski

mm: page_frag: reuse existing space for 'size' and 'pfmemalloc'

2024-11-11T18:56:27+00:00

Currently there is one 'struct page_frag' for every 'struct
sock' and 'struct task_struct', we are about to replace the
'struct page_frag' with 'struct page_frag_cache' for them.
Before begin the replacing, we need to ensure the size of
'struct page_frag_cache' is not bigger than the size of
'struct page_frag', as there may be tens of thousands of
'struct sock' and 'struct task_struct' instances in the
system.

By or'ing the page order & pfmemalloc with lower bits of
'va' instead of using 'u16' or 'u32' for page size and 'u8'
for pfmemalloc, we are able to avoid 3 or 5 bytes space waste.
And page address & pfmemalloc & order is unchanged for the
same page in the same 'page_frag_cache' instance, it makes
sense to fit them together.

After this patch, the size of 'struct page_frag_cache' should be
the same as the size of 'struct page_frag'.

CC: Andrew Morton 
CC: Linux-MM 
Signed-off-by: Yunsheng Lin 
Reviewed-by: Alexander Duyck 
Link: https://patch.msgid.link/20241028115343.3405838-7-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski

mm: page_frag: use initial zero offset for page_frag_alloc_align()

2024-11-11T18:56:26+00:00

We are about 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 coalescing 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 avoid the disadvantages as much
as possible.

1. https://lore.kernel.org/all/f4abe71b3439b39d17a6fb2d410180f367cadf5c.camel@gmail.com/

CC: Andrew Morton 
CC: Linux-MM 
Signed-off-by: Yunsheng Lin 
Reviewed-by: Alexander Duyck 
Link: https://patch.msgid.link/20241028115343.3405838-4-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski

mm: move the page fragment allocator from page_alloc into its own file

2024-11-11T18:56:26+00:00

Inspired by [1], move the page fragment allocator from page_alloc
into its own c file and header file, as we are about to make more
change for it to replace another page_frag implementation in
sock.c

As this patchset is going to replace 'struct page_frag' with
'struct page_frag_cache' in sched.h, including page_frag_cache.h
in sched.h has a compiler error caused by interdependence between
mm_types.h and mm.h for asm-offsets.c, see [2]. So avoid the compiler
error by moving 'struct page_frag_cache' to mm_types_task.h as
suggested by Alexander, see [3].

1. https://lore.kernel.org/all/20230411160902.4134381-3-dhowells@redhat.com/
2. https://lore.kernel.org/all/15623dac-9358-4597-b3ee-3694a5956920@gmail.com/
3. https://lore.kernel.org/all/CAKgT0UdH1yD=LSCXFJ=YM_aiA4OomD-2wXykO42bizaWMt_HOA@mail.gmail.com/
CC: David Howells 
CC: Linux-MM 
Signed-off-by: Yunsheng Lin 
Acked-by: Andrew Morton 
Reviewed-by: Alexander Duyck 
Link: https://patch.msgid.link/20241028115343.3405838-3-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski