v0.5 Performance Improvement on Long Max-Seqlen

[guyueh1]

Tracking items to improve performance for long max-seqlen workloads, including training and generation performance at long context.

[guyueh1]

@youngeunkwon0405 you can create sub-issues once you identified concrete items; If they are general items not async specific you can assign them to me.

[youngeunkwon0405]

Sure I will do.