[PATCH net-next v7 00/15] First try to replace page_frag with page_frag_cache

From: Yunsheng Lin
Date: Fri Jun 07 2024 - 08:41:44 EST

After [1], there are still two implementations for page frag:

1. mm/page_alloc.c: net stack seems to be using it in the
rx part with 'struct page_frag_cache' and the main API
being page_frag_alloc_align().
2. net/core/sock.c: net stack seems to be using it in the
tx part with 'struct page_frag' and the main API being
skb_page_frag_refill().

This patchset tries to unfiy the page frag implementation
by replacing page_frag with page_frag_cache for sk_page_frag()
first. net_high_order_alloc_disable_key for the implementation
in net/core/sock.c doesn't seems matter that much now have
have pcp support for high-order pages in commit 44042b449872
("mm/page_alloc: allow high-order pages to be stored on the
per-cpu lists").

As the related change is mostly related to networking, so
targeting the net-next. And will try to replace the rest
of page_frag in the follow patchset.

After this patchset:
1. Unify the page frag implementation by taking the best out of
two the existing implementations: we are able to save some space
for the 'page_frag_cache' API user, and avoid 'get_page()' for
the old 'page_frag' API user.
2. Future bugfix and performance can be done in one place, hence
improving maintainability of page_frag's implementation.

Kernel Image changing:
Linux Kernel total | text data bss
------------------------------------------------------
after 45250307 | 27274279 17209996 766032
before 45254134 | 27278118 17209984 766032
delta -3827 | -3839 +12 +0

Performance validation:
1. Using micro-benchmark ko added in patch 1 to test aligned and
non-aligned API performance impact for the existing users, there
is no notiable performance degradation. Instead we seems to some
minor performance boot for both aligned and non-aligned API after
this patchset as below.

2. Use the below netcat test case, we also have some minor
performance boot for repalcing 'page_frag' with 'page_frag_cache'
after this patchset.
server: taskset -c 32 nc -l -k 1234 > /dev/null
client: perf stat -r 200 -- taskset -c 0 head -c 20G /dev/zero | taskset -c 1 nc 127.0.0.1 1234


In order to avoid performance noise as much as possible, the testing
is done in system without any other laod and have enough iterations to
prove the data is stable enogh, complete log for testing is below:

taskset -c 32 nc -l -k 1234 > /dev/null
perf stat -r 200 -- insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17
perf stat -r 200 -- insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_align=1
perf stat -r 200 -- taskset -c 0 head -c 20G /dev/zero | taskset -c 1 nc 127.0.0.1 1234

*After* this patchset:

Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17' (200 runs):

17.829030 task-clock (msec) # 0.001 CPUs utilized ( +- 0.30% )
7 context-switches # 0.386 K/sec ( +- 0.35% )
0 cpu-migrations # 0.003 K/sec ( +- 28.06% )
83 page-faults # 0.005 M/sec ( +- 0.10% )
46303585 cycles # 2.597 GHz ( +- 0.30% )
61119216 instructions # 1.32 insn per cycle ( +- 0.01% )
14811318 branches # 830.742 M/sec ( +- 0.01% )
21046 branch-misses # 0.14% of all branches ( +- 0.09% )

23.856064365 seconds time elapsed ( +- 0.08% )


Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_align=1' (200 runs):

17.628569 task-clock (msec) # 0.001 CPUs utilized ( +- 0.01% )
7 context-switches # 0.397 K/sec ( +- 0.12% )
0 cpu-migrations # 0.000 K/sec
83 page-faults # 0.005 M/sec ( +- 0.10% )
45785943 cycles # 2.597 GHz ( +- 0.01% )
60043610 instructions # 1.31 insn per cycle ( +- 0.01% )
14550182 branches # 825.375 M/sec ( +- 0.01% )
21492 branch-misses # 0.15% of all branches ( +- 0.08% )

23.443927103 seconds time elapsed ( +- 0.05% )

Performance counter stats for 'taskset -c 0 head -c 20G /dev/zero' (200 runs):

16626.042731 task-clock (msec) # 0.607 CPUs utilized ( +- 0.03% )
3291020 context-switches # 0.198 M/sec ( +- 0.05% )
1 cpu-migrations # 0.000 K/sec ( +- 0.50% )
85 page-faults # 0.005 K/sec ( +- 0.16% )
30581044838 cycles # 1.839 GHz ( +- 0.05% )
34962744631 instructions # 1.14 insn per cycle ( +- 0.01% )
6483883671 branches # 389.984 M/sec ( +- 0.02% )
99624551 branch-misses # 1.54% of all branches ( +- 0.17% )

27.370305077 seconds time elapsed ( +- 0.01% )


*Before* this patchset:

Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17' (200 runs):

18.143552 task-clock (msec) # 0.001 CPUs utilized ( +- 0.28% )
7 context-switches # 0.382 K/sec ( +- 0.28% )
1 cpu-migrations # 0.056 K/sec ( +- 0.97% )
83 page-faults # 0.005 M/sec ( +- 0.10% )
47105569 cycles # 2.596 GHz ( +- 0.28% )
60628757 instructions # 1.29 insn per cycle ( +- 0.04% )
14686743 branches # 809.475 M/sec ( +- 0.04% )
21826 branch-misses # 0.15% of all branches ( +- 0.12% )

23.918006193 seconds time elapsed ( +- 0.10% )

Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_align=1' (200 runs):

21.726393 task-clock (msec) # 0.001 CPUs utilized ( +- 0.72% )
7 context-switches # 0.321 K/sec ( +- 0.24% )
1 cpu-migrations # 0.047 K/sec ( +- 0.85% )
83 page-faults # 0.004 M/sec ( +- 0.10% )
56422898 cycles # 2.597 GHz ( +- 0.72% )
61271860 instructions # 1.09 insn per cycle ( +- 0.05% )
14837500 branches # 682.925 M/sec ( +- 0.05% )
21484 branch-misses # 0.14% of all branches ( +- 0.10% )

23.876306259 seconds time elapsed ( +- 0.13% )

Performance counter stats for 'taskset -c 0 head -c 20G /dev/zero' (200 runs):

17364.040855 task-clock (msec) # 0.624 CPUs utilized ( +- 0.02% )
3340375 context-switches # 0.192 M/sec ( +- 0.06% )
1 cpu-migrations # 0.000 K/sec
85 page-faults # 0.005 K/sec ( +- 0.15% )
32077623335 cycles # 1.847 GHz ( +- 0.03% )
35121047596 instructions # 1.09 insn per cycle ( +- 0.01% )
6519872824 branches # 375.481 M/sec ( +- 0.02% )
101877022 branch-misses # 1.56% of all branches ( +- 0.14% )

27.842745343 seconds time elapsed ( +- 0.02% )


Note, ipv4-udp, ipv6-tcp and ipv6-udp is also tested with the below script:
nc -u -l -k 1234 > /dev/null
perf stat -r 4 -- head -c 51200000000 /dev/zero | nc -N -u 127.0.0.1 1234

nc -l6 -k 1234 > /dev/null
perf stat -r 4 -- head -c 51200000000 /dev/zero | nc -N ::1 1234

nc -l6 -k -u 1234 > /dev/null
perf stat -r 4 -- head -c 51200000000 /dev/zero | nc -u -N ::1 1234

CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>

1. https://lore.kernel.org/all/20240228093013.8263-1-linyunsheng@xxxxxxxxxx/

Change log:
V7: Fix doc build warning and error.

V6:
1. Fix some typo and compiler error for x86 pointed out by Jakub and
Simon.
2. Add two refactoring and optimization patches.

V5:
1. Add page_frag_alloc_pg() API for tls_device.c case and refactor
some implementation, update kernel bin size changing as bin size
is increased after that.
2. Add ack from Mat.

RFC v4:
1. Update doc according to Randy and Mat's suggestion.
2. Change probe API to "probe" for a specific amount of available space,
rather than "nonzero" space according to Mat's suggestion.
3. Retest and update the test result.

v3:
1. Use new layout for 'struct page_frag_cache' as the discussion
with Alexander and other sugeestions from Alexander.
2. Add probe API to address Mat' comment about mptcp use case.
3. Some doc updating according to Bagas' suggestion.

v2:
1. reorder test module to patch 1.
2. split doc and maintainer updating to two patches.
3. refactor the page_frag before moving.
4. fix a type and 'static' warning in test module.
5. add a patch for xtensa arch to enable using get_order() in
BUILD_BUG_ON().
6. Add test case and performance data for the socket code.


Yunsheng Lin (15):
mm: page_frag: add a test module for page_frag
xtensa: remove the get_order() implementation
mm: page_frag: use free_unref_page() to free page fragment
mm: move the page fragment allocator from page_alloc into its own file
mm: page_frag: use initial zero offset for page_frag_alloc_align()
mm: page_frag: add '_va' suffix to page_frag API
mm: page_frag: avoid caller accessing 'page_frag_cache' directly
mm: page_frag: reuse existing space for 'size' and 'pfmemalloc'
mm: page_frag: some minor refactoring before adding new API
mm: page_frag: use __alloc_pages() to replace alloc_pages_node()
net: introduce the skb_copy_to_va_nocache() helper
mm: page_frag: introduce prepare/probe/commit API
net: replace page_frag with page_frag_cache
mm: page_frag: update documentation for page_frag
mm: page_frag: add a entry in MAINTAINERS for page_frag

Documentation/mm/page_frags.rst | 163 +++++++-
MAINTAINERS | 11 +
arch/xtensa/include/asm/page.h | 18 -
.../chelsio/inline_crypto/chtls/chtls.h | 3 -
.../chelsio/inline_crypto/chtls/chtls_io.c | 100 ++---
.../chelsio/inline_crypto/chtls/chtls_main.c | 3 -
drivers/net/ethernet/google/gve/gve_rx.c | 4 +-
drivers/net/ethernet/intel/ice/ice_txrx.c | 2 +-
drivers/net/ethernet/intel/ice/ice_txrx.h | 2 +-
drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 2 +-
.../net/ethernet/intel/ixgbevf/ixgbevf_main.c | 4 +-
.../marvell/octeontx2/nic/otx2_common.c | 2 +-
drivers/net/ethernet/mediatek/mtk_wed_wo.c | 4 +-
drivers/net/tun.c | 44 +-
drivers/nvme/host/tcp.c | 8 +-
drivers/nvme/target/tcp.c | 22 +-
drivers/vhost/net.c | 8 +-
include/linux/gfp.h | 22 -
include/linux/mm_types.h | 18 -
include/linux/page_frag_cache.h | 299 ++++++++++++++
include/linux/sched.h | 3 +-
include/linux/skbuff.h | 7 +-
include/net/sock.h | 29 +-
kernel/bpf/cpumap.c | 2 +-
kernel/exit.c | 3 +-
kernel/fork.c | 3 +-
mm/Kconfig.debug | 8 +
mm/Makefile | 2 +
mm/page_alloc.c | 136 ------
mm/page_frag_cache.c | 349 ++++++++++++++++
mm/page_frag_test.c | 390 ++++++++++++++++++
net/core/skbuff.c | 83 ++--
net/core/skmsg.c | 22 +-
net/core/sock.c | 46 ++-
net/core/xdp.c | 2 +-
net/ipv4/ip_output.c | 33 +-
net/ipv4/tcp.c | 35 +-
net/ipv4/tcp_output.c | 28 +-
net/ipv6/ip6_output.c | 33 +-
net/kcm/kcmsock.c | 30 +-
net/mptcp/protocol.c | 67 +--
net/rxrpc/conn_object.c | 4 +-
net/rxrpc/local_object.c | 4 +-
net/rxrpc/txbuf.c | 15 +-
net/sched/em_meta.c | 2 +-
net/sunrpc/svcsock.c | 12 +-
net/tls/tls_device.c | 137 +++---
47 files changed, 1644 insertions(+), 580 deletions(-)
create mode 100644 include/linux/page_frag_cache.h
create mode 100644 mm/page_frag_cache.c
create mode 100644 mm/page_frag_test.c

--
2.33.0