Memory CO-RE

[thiagoftsm]

Summary

This PR is adding CO-RE algorithms to all threads related to memory actions.
We are also doing small changes in directory cache and cachestat to speed up the thread loading.
When I was developing this PR, the logic for commits was (exceptions can happen):

Commits

1. Move load from main thread to a helper
2. Add global variables used to test `btf` symbols.
3. Add CO-RE code
4. Change config file for thread.

Test Plan

1. Clone this Branch
2. Change your /etc/netdata/ebpf.d.conf to:

[ebpf programs]
    cachestat = yes
    dcstat = yes
    swap = yes

6. Compile this branch
7. Start netdata and wait few seconds.
8. Run the following script:

Script:

#!/bin/bash
curl -k -o load_ebpf.txt http://localhost:19999/api/v1/data?chart=netdata.ebpf_load_methods
curl -k -o global_cachestat.txt http://localhost:19999/api/v1/data?chart=mem.cachestat_ratio
curl -k -o apps_cachestat_dirties.txt http://localhost:19999/api/v1/data?chart=apps.cachestat_dirties
curl -k -o apps_dc_reference.txt http://localhost:19999/api/v1/data?chart=apps.dc_reference
curl -k -o apps_swap_read_call.txt http://localhost:19999/api/v1/data?chart=apps.swap_read_call
curl -k -o services_cachestat.txt http://localhost:19999/api/v1/data?chart=services.cachestat_ratio
grep eBPF /var/log/netdata/* > log.txt

Additional Information

On Slackware I am not adding any cgroup chart, because Slackware does not have systemd ( 🥳 ).
You can get all reports using this link.

This PR was already tested on:

Linux Distribution	kernel version	Load Chart	LOG	Global Cachestat	APPS cachestat	Services Cachestat	Apps SWAP	Apps Directory Cache
Slackware Current	5.17.3	slackware_5_17_3_load_ebpf.txt	slackware_5_17_3_log.txt	slackware_5_17_3_global_cachestat.txt	slackware_5_17_3_apps_cachestat_dirties.txt		slackware_5_17_3_apps_swap_read_call.txt	slackware_5_17_3_apps_dc_reference.txt
Arch Linux	5.17.1-arch1	arch_5_17_1_load_ebpf.txt	arch_5_17_1_log.txt	arch_5_17_1_global_cachestat.txt	arch_5_17_1_apps_cachestat_dirties.txt	arch_5_17_1_services_cachestat.txt	arch_5_17_1_apps_swap_read_call.txt	arch_5_17_1_apps_dc_reference.txt
Ubuntu 21.04	5.11.0-49-generic	ubuntu_5_11_load_ebpf.txt	ubuntu_5_11_log.txt	ubuntu_5_11_global_cachestat.txt	ubuntu_5_11_apps_cachestat_dirties.txt	ubuntu_5_11_services_cachestat.txt	ubuntu_5_11_apps_swap_read_call.txt	ubuntu_5_11_apps_dc_reference.txt
Manjaro 21.1	5.10.109-1	manjaro_5_10_1_load_ebpf.txt	manjaro_5_10_1_log.txt	manjaro_5_10_1_global_cachestat.txt	manjaro_5_10_1_apps_cachestat_dirties.txt	manjaro_5_10_1_services_cachestat.txt	manjaro_5_10_1_apps_swap_read_call.txt	manjaro_5_10_1_apps_dc_reference.txt
Alma 8.5	4.18.0-348.20.1.el8_5.x86_64	alma_4_18_load_ebpf.txt	alma_4_18_log.txt	alma_4_18_global_cachestat.txt	alma_4_18_apps_cachestat_dirties.txt	alma_4_18_services_cachestat.txt	alma_4_18_apps_swap_read_call.txt	alma_4_18_apps_dc_reference.txt
Slackware 15.0	4.14.266	slackware_4_14_266_load_ebpf.txt	slackware_4_14_266_log.txt	slackware_4_14_266_global_cachestat.txt	slackware_4_14_266_apps_cachestat_dirties.txt		slackware_4_14_266_apps_swap_read_call.txt	slackware_4_14_266_apps_dc_reference.txt

For users: How does this change affect me?

Describe the PR affects users: - Which area of Netdata is affected by the change? Dashboard, and performance. - Can they see the change or is it an under the hood? If they can see it, where? This is not visible for users, because we are changing the way we collect data. - How is the user impacted by the change? Performance. - What are there any benefits of the change? Charts used to monitor SWAP, Cachestat, and Directory cache will affect less the host, because users will use `trampolines` instead `kprobes`

[vlvkobal]

collectors/ebpf.plugin/ebpf_dcstat.c: In function 'ebpf_dc_load_and_attach':
collectors/ebpf.plugin/ebpf_dcstat.c:191:29: warning: unused variable 'mt' [-Wunused-variable]
  191 |     netdata_ebpf_targets_t *mt = em->targets;
      |   

[vlvkobal]

BTW, do you plan to use libuv threading and synchronization primitives in the eBPF plugin?

[thiagoftsm]

This is a change that we cannot discard, mainly considering that Microsoft has working to improve eBPF support. Considering that we are right now working to finish the CO-RE integration, this could be the next work with plugin (ping @cpipilas ).

[thiagoftsm]

collectors/ebpf.plugin/ebpf_dcstat.c:191:29: warning: unused variable 'mt' [-Wunused-variable]
191 | netdata_ebpf_targets_t *mt = em->targets;

It was fixed with last commit, thanks to report!