While comparing Lustre 1.8 series with latest master release in client. Server is running the same 2.5 series. we found there is big file removal regression.

Testing command is:

1. mpirun -bind-to core:overload-allowed --map-by ppr:32:node --allow-run-as-root -np 512 -hostfile ./hostfile.32 ./mdtest -n 2000 -i 3 -p 10 -u -d /lustre_ {0-31}

   /mdtest.out -F -N 32

While comparing file removal performance between 1.8 and master is:
61476.175 op/seconds VS 39640.455 op/seconds.

Big regression, isn't it?

Notice here we need use '-N' option for mdtest, the problem seems only reproducible under multiple clients. Attachment is modified mdtest source codes which could help reproduce this problem.