Tejun Heo [off-list ref] writes:

This patch implements per-blkg request_list.  Each blkg has its own
request_list and any IO allocates its request from the matching blkg
making blkcgs completely isolated in terms of request allocation.

So, nr_requests is now actually nr_requests * # of blk cgroups.  Is that
right?  Are you at all concerned about the amount of memory that can be
tied up as the number of cgroups increases?

Cheers,
Jeff