[syncd][bcm] Enable SAI bulk mode in config_syncd_bcm

[vpandian-nokia]

Summary

• Enable syncd -l in config_syncd_bcm() so Broadcom platforms use SAI bulk mode by default.
• Keep the change localized to the Broadcom syncd init path and leave other ASIC handlers unchanged.
• This is intended to improve route programming performance on Broadcom DNX/XGS platforms and aligns with Broadcom SAI PERFMON usage.

Test plan

• Build image successfully with the updated syncd/scripts/syncd_init_common.sh.
• Boot DUT with the new image.
• Verify live syncd command line includes -l.
• Verify syncd and swss containers remain stable after boot.
• Verify no immediate startup regressions in docker logs syncd and docker logs swss.
• Run normal route-scale / convergence workload on the DUT.

[mssonicbld]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[vpandian-nokia]

@deepak-singhal0408

[deepak-singhal0408]

@rlhui @arlakshm for viz.

[vpandian-nokia]

Additional DUT performance data for this change:

The measured gain with this change is in the range of about 8% to 10% on a DUT with AMD EPYC 3251 8-Core 2.5GHz and 16 GB DRAM, using route-download workloads of 300K IPv4 or 300K IPv6 routes.

[deepak-singhal0408]

@prsunny @prabhataravind for viz.
@arista-nwolfe @eswaran-nexthop for viz.

[rlhui]

please confirm sonic-mgmt tests/pfcwd related are passing with this change

[deepak-singhal0408]

@vpandian-nokia could you provide more data on sonic-mgmt Nightly tests with this change? And also the CI is failing. please help check.

[vpandian-nokia]

@vpandian-nokia could you provide more data on sonic-mgmt Nightly tests with this change? And also the CI is failing. please help check.

Thanks for the note. We are working on the sonic-mgmt / nightly validation for this change, including the earlier pfcwd-related ask, and will share the results once they are available.

We are also checking the current CI failure in parallel. The /azp run trigger appears to require additional permissions here. Could you please help rerun the Azure pipeline for this PR so we can confirm whether the failure reproduces?

[vpandian-nokia]

/azp run

[azure-pipelines]

Commenter does not have sufficient privileges for PR 1850 in repo sonic-net/sonic-sairedis

[mssonicbld]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[vpandian-nokia]

@vpandian-nokia could you provide more data on sonic-mgmt Nightly tests with this change? And also the CI is failing. please help check.

Thanks for the note. We are working on the sonic-mgmt / nightly validation for this change, including the earlier pfcwd-related ask, and will share the results once they are available.

We are also checking the current CI failure in parallel. The /azp run trigger appears to require additional permissions here. Could you please help rerun the Azure pipeline for this PR so we can confirm whether the failure reproduces?

@deepak-singhal0408 : The rerun shows the current failure is in BuildTrixie amd64 during Run sonic sairedis unit tests, with FlexCounter.bulkChunksize failing. From the unit-test output, the failure is due to repeated object_count expectation mismatches within that test.

I also checked recent master, and there has been a recent failure in the same BuildTrixie amd64 unit-test path there as well, although on a different FlexCounter test. Since this PR only changes the Broadcom config_syncd_bcm() path in syncd_init_common.sh, the current Trixie unit-test failure does not appear obviously attributable to this PR.