Merge branch 'net-sctp-Avoid-allocating-high-order-memory-with-kmalloc'
Konstantin Khorenko says:
====================
net/sctp: Avoid allocating high order memory with kmalloc()
Each SCTP association can have up to 65535 input and output streams.
For each stream type an array of sctp_stream_in or sctp_stream_out
structures is allocated using kmalloc_array() function. This function
allocates physically contiguous memory regions, so this can lead
to allocation of memory regions of very high order, i.e.:
sizeof(struct sctp_stream_out) == 24,
((65535 * 24) / 4096) == 383 memory pages (4096 byte per page),
which means 9th memory order.
This can lead to a memory allocation failures on the systems
under a memory stress.
We actually do not need these arrays of memory to be physically
contiguous. Possible simple solution would be to use kvmalloc()
instread of kmalloc() as kvmalloc() can allocate physically scattered
pages if contiguous pages are not available. But the problem
is that the allocation can happed in a softirq context with
GFP_ATOMIC flag set, and kvmalloc() cannot be used in this scenario.
So the other possible solution is to use flexible arrays instead of
contiguios arrays of memory so that the memory would be allocated
on a per-page basis.
This patchset replaces kvmalloc() with flex_array usage.
It consists of two parts:
* First patch is preparatory - it mechanically wraps all direct
access to assoc->stream.out[] and assoc->stream.in[] arrays
with SCTP_SO() and SCTP_SI() wrappers so that later a direct
array access could be easily changed to an access to a
flex_array (or any other possible alternative).
* Second patch replaces kmalloc_array() with flex_array usage.
v2 changes:
sctp_stream_in() users are updated to provide stream as an argument,
sctp_stream_{in,out}_ptr() are now just sctp_stream_{in,out}().
v3 changes:
Move type chages struct sctp_stream_out -> flex_array to next patch.
Make sctp_stream_{in,out}() static incline and move them to a header.
Performance results (single stream):
====================================
* Kernel: v4.18-rc6 - stock and with 2 patches from Oleg (earlier in this thread)
* Node: CPU (8 cores): Intel(R) Xeon(R) CPU E31230 @ 3.20GHz
RAM: 32 Gb
* netperf: taken from https://github.com/HewlettPackard/netperf.git,
compiled from sources with sctp support
* netperf server and client are run on the same node
* ip link set lo mtu 1500
The script used to run tests:
# cat run_tests.sh
#!/bin/bash
for test in SCTP_STREAM SCTP_STREAM_MANY SCTP_RR SCTP_RR_MANY; do
echo "TEST: $test";
for i in `seq 1 3`; do
echo "Iteration: $i";
set -x
netperf -t $test -H localhost -p 22222 -S 200000,200000 -s 200000,200000 \
-l 60 -- -m 1452;
set +x
done
done
================================================
Results (a bit reformatted to be more readable):
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
v4.18-rc7 v4.18-rc7 + fixes
TEST: SCTP_STREAM
212992 212992 1452 60.21 1125.52 1247.04
212992 212992 1452 60.20 1376.38 1149.95
212992 212992 1452 60.20 1131.40 1163.85
TEST: SCTP_STREAM_MANY
212992 212992 1452 60.00 1111.00 1310.05
212992 212992 1452 60.00 1188.55 1130.50
212992 212992 1452 60.00 1108.06 1162.50
===========
Local /Remote
Socket Size Request Resp. Elapsed Trans.
Send Recv Size Size Time Rate
bytes Bytes bytes bytes secs. per sec
v4.18-rc7 v4.18-rc7 + fixes
TEST: SCTP_RR
212992 212992 1 1 60.00 45486.98 46089.43
212992 212992 1 1 60.00 45584.18 45994.21
212992 212992 1 1 60.00 45703.86 45720.84
TEST: SCTP_RR_MANY
212992 212992 1 1 60.00 40.75 40.77
212992 212992 1 1 60.00 40.58 40.08
212992 212992 1 1 60.00 39.98 39.97
Performance results for many streams:
=====================================
* Kernel: v4.18-rc8 - stock and with 2 patches v3
* Node: CPU (8 cores): Intel(R) Xeon(R) CPU E31230 @ 3.20GHz
RAM: 32 Gb
* sctp_test: https://github.com/sctp/lksctp-tools
* both server and client are run on the same node
* ip link set lo mtu 1500
* sysctl -w vm.max_map_count=65530000 (need it to make memory fragmented)
The script used to run tests:
=============================
# cat run_sctp_test.sh
#!/bin/bash
set -x
uname -r
ip link set lo mtu 1500
swapoff -a
free
cat /proc/buddyinfo
./src/apps/sctp_test -H 127.0.0.1 -P 22222 -l -d 0 &
sleep 3
time ./src/apps/sctp_test -H 127.0.0.1 -P 22221 -h 127.0.0.1 -p 22222 \
-s -c 1 -M 65535 -T -t 1 -x 100000 -d 0 1>/dev/null
killall -9 lt-sctp_test
===============================
Results (a bit reformatted to be more readable):
1) ms stock kernel v4.18-rc8, no memory fragmentation
test 1 test 2 test 3
real 0m14.715s 0m14.593s 0m15.954s
user 0m0.954s 0m0.955s 0m0.854s
sys 0m13.388s 0m12.537s 0m13.749s
2) kernel with fixes, no memory fragmentation
test 1 test 2 test 3
real 0m14.959s 0m14.693s 0m14.762s
user 0m0.948s 0m0.921s 0m0.929s
sys 0m13.538s 0m13.225s 0m13.217s
3) kernel with fixes, memory fragmented
'free':
total used free shared buff/cache available
Mem: 32906008 30555200 302740 764 2048068 266452
Mem: 32906008 30379948 541436 764 1984624 442376
Mem: 32906008 30717312 262380 764 1926316 109908
/proc/buddyinfo:
Node 0, zone Normal 40773 37 34 29 0 0 0 0 0 0 0
Node 0, zone Normal 100332 68 8 4 2 1 1 0 0 0 0
Node 0, zone Normal 31113 7 2 1 0 0 0 0 0 0 0
test 1 test 2 test 3
real 0m14.159s 0m15.252s 0m15.826s
user 0m0.839s 0m1.004s 0m1.048s
sys 0m11.827s 0m14.240s 0m14.778s
====================
Signed-off-by: 
David S. Miller <davem@davemloft.net>
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