Messages in this thread | | | From | Rusty Russell <> | Subject | per-cpu stats in block device: overkill? | Date | Mon, 22 Dec 2008 10:49:43 +1030 |
| |
Hi Jens, Tejun, Jerome,
I've been auditing alloc_per_cpu users, and got to genhd. The code is fairly complex, but I can't help wondering if per-cpu counters are overkill. After all, we have a single queue lock.
The reason I care is that I'm changing alloc_per_cpu to use the static per-cpu area: at 40/80 bytes (32/64 bit) per stat, we'd be restricted to a few hundred disks unless the percpu area is enlarged (in current patches, a cmdline param). Or, I can change genhd to use big_percpu_alloc which will use the current inefficient dynamic per-cpu system until we get dynamic per-cpu regions (if ever).
Cheers, Rusty.
| |