This is part 2 of "Replace page_frag with page_frag_cache",
which introduces the new API and replaces page_frag with
page_frag_cache for sk_page_frag().
The part 1 of "Replace page_frag with page_frag_cache" is in
[1].
After [2], 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 as pcp
is also supported for high-order pages:
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.
Performance validation for part2:
1. Using micro-benchmark ko added in patch 1 to test aligned and
non-aligned API performance impact for the existing users, there
seems to be about 20% performance degradation for refactoring
page_frag to support the new API, which seems to nullify most of
the performance gain in [3] of part1.
2. Use the below netcat test case, there seems to be some minor
performance gain for replacing 'page_frag' with 'page_frag_cache'
using the new page_frag API 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 load and have enough iterations to
prove the data is stable enough, complete log for testing is below:
perf stat -r 200 -- insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_alloc_len=12 nr_test=51200000
perf stat -r 200 -- insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_alloc_len=12 nr_test=51200000 test_align=1
taskset -c 32 nc -l -k 1234 > /dev/null
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 test_alloc_len=12 nr_test=51200000' (200 runs):
18.753187 task-clock (msec) # 0.003 CPUs utilized ( +- 0.44% )
8 context-switches # 0.422 K/sec ( +- 0.30% )
0 cpu-migrations # 0.003 K/sec ( +- 32.09% )
84 page-faults # 0.004 M/sec ( +- 0.08% )
48700826 cycles # 2.597 GHz ( +- 0.44% )
62086543 instructions # 1.27 insn per cycle ( +- 0.03% )
14869358 branches # 792.898 M/sec ( +- 0.03% )
19639 branch-misses # 0.13% of all branches ( +- 0.60% )
7.035285915 seconds time elapsed ( +- 0.06% )
Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_alloc_len=12 nr_test=51200000 test_align=1' (200 runs):
18.442151 task-clock (msec) # 0.006 CPUs utilized ( +- 0.01% )
8 context-switches # 0.422 K/sec ( +- 0.40% )
0 cpu-migrations # 0.001 K/sec ( +- 57.44% )
84 page-faults # 0.005 M/sec ( +- 0.08% )
47890149 cycles # 2.597 GHz ( +- 0.01% )
60718325 instructions # 1.27 insn per cycle ( +- 0.00% )
14570862 branches # 790.085 M/sec ( +- 0.00% )
19613 branch-misses # 0.13% of all branches ( +- 0.12% )
3.210892358 seconds time elapsed ( +- 0.12% )
Performance counter stats for 'taskset -c 0 head -c 20G /dev/zero' (200 runs):
16824.017944 task-clock (msec) # 0.621 CPUs utilized ( +- 0.02% )
2987954 context-switches # 0.178 M/sec ( +- 0.04% )
1 cpu-migrations # 0.000 K/sec
93 page-faults # 0.006 K/sec ( +- 0.09% )
31982647267 cycles # 1.901 GHz ( +- 0.03% )
38907812424 instructions # 1.22 insn per cycle ( +- 0.02% )
7112328962 branches # 422.749 M/sec ( +- 0.03% )
94789062 branch-misses # 1.33% of all branches ( +- 0.21% )
27.104994660 seconds time elapsed ( +- 0.03% )
*Before* this patchset:
Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_alloc_len=12 nr_test=51200000' (200 runs):
18.700051 task-clock (msec) # 0.003 CPUs utilized ( +- 1.04% )
8 context-switches # 0.420 K/sec ( +- 0.31% )
0 cpu-migrations # 0.019 K/sec ( +- 10.16% )
81 page-faults # 0.004 M/sec ( +- 0.09% )
48548980 cycles # 2.596 GHz ( +- 1.04% )
61857980 instructions # 1.27 insn per cycle ( +- 0.09% )
14814201 branches # 792.201 M/sec ( +- 0.08% )
42007 branch-misses # 0.28% of all branches ( +- 0.11% )
5.565806266 seconds time elapsed ( +- 0.08% )
Performance counter stats for 'insmod ./page_frag_test.ko test_push_cpu=16 test_pop_cpu=17 test_alloc_len=12 nr_test=51200000 test_align=1' (200 runs):
18.468618 task-clock (msec) # 0.007 CPUs utilized ( +- 1.14% )
8 context-switches # 0.422 K/sec ( +- 0.43% )
0 cpu-migrations # 0.026 K/sec ( +- 7.89% )
81 page-faults # 0.004 M/sec ( +- 0.08% )
47950150 cycles # 2.596 GHz ( +- 1.14% )
61745530 instructions # 1.29 insn per cycle ( +- 0.09% )
14787783 branches # 800.698 M/sec ( +- 0.08% )
41734 branch-misses # 0.28% of all branches ( +- 0.09% )
2.584180919 seconds time elapsed ( +- 0.04% )
Performance counter stats for 'taskset -c 0 head -c 20G /dev/zero' (200 runs):
17105.617450 task-clock (msec) # 0.599 CPUs utilized ( +- 0.02% )
2822654 context-switches # 0.165 M/sec ( +- 0.03% )
1 cpu-migrations # 0.000 K/sec ( +- 0.50% )
93 page-faults # 0.005 K/sec ( +- 0.09% )
31819244033 cycles # 1.860 GHz ( +- 0.03% )
37297412811 instructions # 1.17 insn per cycle ( +- 0.01% )
6676699757 branches # 390.322 M/sec ( +- 0.01% )
325102016 branch-misses # 4.87% of all branches ( +- 0.06% )
28.568053622 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 -u 127.0.0.1 1234
nc -l6 -k 1234 > /dev/null
perf stat -r 4 -- head -c 51200000000 /dev/zero | nc ::1 1234
nc -l6 -k -u 1234 > /dev/null
perf stat -r 4 -- head -c 51200000000 /dev/zero | nc -u ::1 1234
CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>
CC: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Linux-MM <linux-mm@xxxxxxxxx>
1. https://lore.kernel.org/all/20241028115343.3405838-1-linyunsheng@xxxxxxxxxx/
2. https://lore.kernel.org/all/20240228093013.8263-1-linyunsheng@xxxxxxxxxx/
3. https://lore.kernel.org/all/472a7a09-387f-480d-b66c-761e0b6192ef@xxxxxxxxxx/
V1: Rebase on latest net-next tree and redo the performance test.
RFC:
1. CC Andrew and MM ML explicitly.
2. Split into two parts according to the discussion in v22, and this is
the part-2.
3. Split 'introduce new API' patch to more patches to make more reviewable
and easier to discuss.
Yunsheng Lin (10):
mm: page_frag: some minor refactoring before adding new API
net: rename skb_copy_to_page_nocache() helper
mm: page_frag: update documentation for page_frag
mm: page_frag: introduce page_frag_alloc_abort() related API
mm: page_frag: introduce refill prepare & commit API
mm: page_frag: introduce alloc_refill prepare & commit API
mm: page_frag: introduce probe related API
mm: page_frag: add testing for the newly added API
net: replace page_frag with page_frag_cache
mm: page_frag: add an entry in MAINTAINERS for page_frag
Documentation/mm/page_frags.rst | 207 ++++++++++-
MAINTAINERS | 12 +
.../chelsio/inline_crypto/chtls/chtls.h | 3 -
.../chelsio/inline_crypto/chtls/chtls_io.c | 101 ++----
.../chelsio/inline_crypto/chtls/chtls_main.c | 3 -
drivers/net/tun.c | 47 ++-
include/linux/page_frag_cache.h | 330 +++++++++++++++++-
include/linux/sched.h | 2 +-
include/net/sock.h | 30 +-
kernel/exit.c | 3 +-
kernel/fork.c | 3 +-
mm/page_frag_cache.c | 108 +++++-
net/core/skbuff.c | 58 +--
net/core/skmsg.c | 12 +-
net/core/sock.c | 32 +-
net/ipv4/ip_output.c | 28 +-
net/ipv4/tcp.c | 26 +-
net/ipv4/tcp_output.c | 25 +-
net/ipv6/ip6_output.c | 28 +-
net/kcm/kcmsock.c | 21 +-
net/mptcp/protocol.c | 47 ++-
net/tls/tls_device.c | 100 ++++--
.../selftests/mm/page_frag/page_frag_test.c | 76 +++-
tools/testing/selftests/mm/run_vmtests.sh | 4 +
tools/testing/selftests/mm/test_page_frag.sh | 27 ++
25 files changed, 1045 insertions(+), 288 deletions(-)
--
2.33.0
