Web app-friendly thread locals for gc-free logging (was: upgrade to log4j2 causes too frequent minor gc)

We used slf4j+log1.2 in our spring web application. Due to the log4j1.0 performance issue, we upgrade it to log4j2. When it goes to production, it experienced very frequent minor gc (once per second) even though the eden area is not full. For example, the eden area just occupied 10%, the minor gc also happens. The issue disappears when rolling back to log4j1.2.

Can anyone show some hints on diagnose this issue? Thanks!