Investigate performance regression of show.json action (source) for Projects::BlobController
Recently the performance of the show.json action (source) for Projects::BlobController has degraded notably from around 1s up to 3s:
* Environment: 10k
* Environment Version: 15.4.0-pre `b5367e7add2`
* Option: 60s_200rps
* Date: 2022-09-06
* Run Time: 1h 38m 30.8s (Start: 04:43:51 UTC, End: 06:22:21 UTC)
* GPT Version: v2.11.0
NAME | RPS | RPS RESULT | TTFB AVG | TTFB P90 | REQ STATUS | RESULT
---------------------------------------------------------|-------|----------------------|-----------|----------------------|----------------|---------
web_project_file_source | 20/s | 12.09/s (>1.60/s) | 1708.70ms | 2901.08ms (<1700ms) | 100.00% (>99%) | FAILED¹²
http_req_waiting..................: avg=1708.70ms min=407.46ms med=2703.92ms max=4775.96ms p(90)=2901.08ms p(95)=3506.09ms
✗ { endpoint:file?format=json }...: avg=2919.21ms min=2700.16ms med=2824.63ms max=4775.96ms p(90)=3502.53ms p(95)=3587.95ms
✓ { endpoint:file }...............: avg=498.20ms min=407.46ms med=440.99ms max=3586.27ms p(90)=501.03ms p(95)=525.99ms 
Investigations so far suggest this is related to more blame information being shown on the page but after some changes the endpoint still has degraded performance and more investigation is required to bring the endpoint back to similar levels.
Based on our performance targets the endpoint is currently performing in the severity2 tier.
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Edited by Sean Carroll