Re: [RFC PATCH net-next 0/3] sock: Be aware of memcg pressure on alloc

[Abel Wu <wuyun.abel@bytedance.com>]

Friendly ping :)

On 9/1/23 2:21 PM, Abel Wu wrote:
> As a cloud service provider, we encountered a problem in our production
> environment during the transition from cgroup v1 to v2 (partly due to the
> heavy taxes of accounting socket memory in v1). Say one workload behaves
> fine in cgroupv1 with memcg limit configured to 10GB memory and another
> 1GB tcpmem, but will suck (or even be OOM-killed) in v2 with 11GB memory
> due to burst memory usage on socket, since there is no specific limit for
> socket memory in cgroupv2 and relies largely on workloads doing traffic
> control themselves.
> 
> It's rational for the workloads to build some traffic control to better
> utilize the resources they bought, but from kernel's point of view it's
> also reasonable to suppress the allocation of socket memory once there is
> a shortage of free memory, given that performance degradation is usually
> better than failure.
> 
> This patchset aims to be more conservative on alloc for pressure-aware
> sockets under global and/or memcg pressure, to avoid further memstall or
> possibly OOM in such case. The patchset includes:
> 
>    1/3: simple code cleanup, no functional change intended.
>    2/3: record memcg pressure level to enable fine-grained control.
>    3/3: throttle alloc for pressure-aware sockets under pressure.
> 
> The whole patchset focuses on the pressure-aware protocols, and should
> have no/little impact on pressure-unaware protocols like UDP etc.
> 
> Tested on Intel Xeon(R) Platinum 8260, a dual socket machine containing 2
> NUMA nodes each of which has 24C/48T. All the benchmarks are done inside a
> separate memcg in a clean host.
> 
>    baseline:	net-next c639a708a0b8
>    compare:	baseline + patchset
> 
> case            	load    	baseline(std%)	compare%( std%)
> tbench-loopback        	thread-24	 1.00 (  0.50)	 -0.98 (  0.87)
> tbench-loopback        	thread-48	 1.00 (  0.76)	 -0.29 (  0.92)
> tbench-loopback        	thread-72	 1.00 (  0.75)	 +1.51 (  0.14)
> tbench-loopback        	thread-96	 1.00 (  4.11)	 +1.29 (  3.73)
> tbench-loopback        	thread-192	 1.00 (  3.52)	 +1.44 (  3.30)
> TCP_RR          	thread-24	 1.00 (  1.87)	 -0.87 (  2.40)
> TCP_RR          	thread-48	 1.00 (  0.92)	 -0.22 (  1.61)
> TCP_RR          	thread-72	 1.00 (  2.35)	 +2.42 (  2.27)
> TCP_RR          	thread-96	 1.00 (  2.66)	 -1.37 (  3.02)
> TCP_RR          	thread-192	 1.00 ( 13.25)	 +0.29 ( 11.80)
> TCP_STREAM      	thread-24	 1.00 (  1.26)	 -0.75 (  0.87)
> TCP_STREAM      	thread-48	 1.00 (  0.29)	 -1.55 (  0.14)
> TCP_STREAM      	thread-72	 1.00 (  0.05)	 -1.59 (  0.05)
> TCP_STREAM      	thread-96	 1.00 (  0.19)	 -0.06 (  0.29)
> TCP_STREAM      	thread-192	 1.00 (  0.23)	 -0.01 (  0.28)
> UDP_RR          	thread-24	 1.00 (  2.27)	 +0.33 (  2.82)
> UDP_RR          	thread-48	 1.00 (  1.25)	 -0.30 (  1.21)
> UDP_RR          	thread-72	 1.00 (  2.54)	 +2.99 (  2.34)
> UDP_RR          	thread-96	 1.00 (  4.76)	 +2.49 (  2.19)
> UDP_RR          	thread-192	 1.00 ( 14.43)	 -0.02 ( 12.98)
> UDP_STREAM      	thread-24	 1.00 (107.41)	 -0.48 (106.93)
> UDP_STREAM      	thread-48	 1.00 (100.85)	 +1.38 (100.59)
> UDP_STREAM      	thread-72	 1.00 (103.43)	 +1.40 (103.48)
> UDP_STREAM      	thread-96	 1.00 ( 99.91)	 -0.25 (100.06)
> UDP_STREAM      	thread-192	 1.00 (109.83)	 -3.67 (104.12)
> 
> As patch 3 moves forward traversal of cgroup hierarchy for pressure-aware
> protocols, which could turn a conditional overhead into constant, tests
> running inside 5-level-depth cgroups are also performed.
> 
> case            	load    	baseline(std%)	compare%( std%)
> tbench-loopback        	thread-24	 1.00 (  0.59)	 +0.68 (  0.09)
> tbench-loopback        	thread-48	 1.00 (  0.16)	 +0.01 (  0.26)
> tbench-loopback        	thread-72	 1.00 (  0.34)	 -0.67 (  0.48)
> tbench-loopback        	thread-96	 1.00 (  4.40)	 -3.27 (  4.84)
> tbench-loopback        	thread-192	 1.00 (  0.49)	 -1.07 (  1.18)
> TCP_RR          	thread-24	 1.00 (  2.40)	 -0.34 (  2.49)
> TCP_RR          	thread-48	 1.00 (  1.62)	 -0.48 (  1.35)
> TCP_RR          	thread-72	 1.00 (  1.26)	 +0.46 (  0.95)
> TCP_RR          	thread-96	 1.00 (  2.98)	 +0.13 (  2.64)
> TCP_RR          	thread-192	 1.00 ( 13.75)	 -0.20 ( 15.42)
> TCP_STREAM      	thread-24	 1.00 (  0.21)	 +0.68 (  1.02)
> TCP_STREAM      	thread-48	 1.00 (  0.20)	 -1.41 (  0.01)
> TCP_STREAM      	thread-72	 1.00 (  0.09)	 -1.23 (  0.19)
> TCP_STREAM      	thread-96	 1.00 (  0.01)	 +0.01 (  0.01)
> TCP_STREAM      	thread-192	 1.00 (  0.20)	 -0.02 (  0.25)
> UDP_RR          	thread-24	 1.00 (  2.20)	 +0.84 ( 17.45)
> UDP_RR          	thread-48	 1.00 (  1.34)	 -0.73 (  1.12)
> UDP_RR          	thread-72	 1.00 (  2.32)	 +0.49 (  2.11)
> UDP_RR          	thread-96	 1.00 (  2.36)	 +0.53 (  2.42)
> UDP_RR          	thread-192	 1.00 ( 16.34)	 -0.67 ( 14.06)
> UDP_STREAM      	thread-24	 1.00 (106.55)	 -0.70 (107.13)
> UDP_STREAM      	thread-48	 1.00 (105.11)	 +1.60 (103.48)
> UDP_STREAM      	thread-72	 1.00 (100.60)	 +1.98 (101.13)
> UDP_STREAM      	thread-96	 1.00 ( 99.91)	 +2.59 (101.04)
> UDP_STREAM      	thread-192	 1.00 (135.39)	 -2.51 (108.00)
> 
> As expected, no obvious performance gain or loss observed. As for the
> issue we encountered, this patchset provides better worst-case behavior
> that such OOM cases are reduced at some extent. While further fine-
> grained traffic control is what the workloads need to think about.
> 
> Comments are welcomed! Thanks!
> 
> Abel Wu (3):
>    sock: Code cleanup on __sk_mem_raise_allocated()
>    net-memcg: Record pressure level when under pressure
>    sock: Throttle pressure-aware sockets under pressure
> 
>   include/linux/memcontrol.h | 39 +++++++++++++++++++++++++----
>   include/net/sock.h         |  2 +-
>   include/net/tcp.h          |  2 +-
>   mm/vmpressure.c            |  9 ++++++-
>   net/core/sock.c            | 51 +++++++++++++++++++++++++++++---------
>   5 files changed, 83 insertions(+), 20 deletions(-)
>