Messages in this thread | | | Date | Thu, 9 Nov 2023 10:09:46 -0800 | Subject | Re: [GIT PULL v2] Networking for 6.7 | From | Yonghong Song <> |
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On 11/9/23 8:14 AM, Kirill A. Shutemov wrote: > On Thu, Nov 09, 2023 at 08:01:39AM -0800, Alexei Starovoitov wrote: >> On Thu, Nov 9, 2023 at 7:49 AM Kirill A. Shutemov <kirill@shutemov.name> wrote: >>> On Tue, Oct 31, 2023 at 02:09:48PM -0700, Jakub Kicinski wrote: >>>> bpf: Add support for non-fix-size percpu mem allocation >>> Recent changes in BPF increased per-CPU memory consumption a lot. >>> >>> On virtual machine with 288 CPUs, per-CPU consumtion increased from 111 MB >>> to 969 MB, or 8.7x. >>> >>> I've bisected it to the commit 41a5db8d8161 ("bpf: Add support for >>> non-fix-size percpu mem allocation"), which part of the pull request. >> Hmm. This is unexpected. Thank you for reporting. >> >> How did you measure this 111 MB vs 969 MB ? >> Pls share the steps to reproduce. > Boot VMM with 288 (qemu-system-x86_64 -smp 288) and check Percpu: field of > /proc/meminfo.
I did some experiments with my VM. My VM currently supports up to 255 cpus, so I tried 4/32/252 number of cpus. For a particular number of cpus, two experiments are done: (1). bpf-percpu-mem-prefill (2). no-bpf-percpu-mem-prefill
For 4 cpu: bpf-percpu-mem-prefill: Percpu: 2000 kB no-bpf-percpu-mem-prefill: Percpu: 1808 kB
bpf-percpu-mem-prefill percpu cost: (2000 - 1808)/4 KB = 48KB
For 32 cpus: bpf-percpu-mem-prefill: Percpu: 25344 kB no-bpf-percpu-mem-prefill: Percpu: 14464 kB
bpf-percpu-mem-prefill percpu cost: (25344 - 14464)/4 KB = 340KB
For 252 cpus: bpf-percpu-mem-prefill: Percpu: 230912 kB no-bpf-percpu-mem-prefill: Percpu: 57856 kB
bpf-percpu-mem-prefill percpu cost: (230912 - 57856)/4 KB = 686KB
I am not able to reproduce the dramatic number from 111 MB to 969 MB. My number with 252 cpus is from ~58MB to ~231MB.
I appears that percpu allocation cost goes up when the number of cpus is increased.
I will continue to debug this. Thanks!
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