Re: [patch 00/41] cpu alloc / cpu ops v3: Optimize per cpu access

Christoph Lameter
2008-05-30T06:22:47Z

On Thu, 29 May 2008, Andrew Morton wrote:

> ext3 maintains three percpu_counters per mount. Each percpu_counter
> does one percpu_alloc. People can mount an arbitrary number of ext3
> filesystems!

But its 4 bytes per alloc right?

> Another: there are two percpu_counters (and hence two percpu_alloc()s)
> per backing_dev_info. One backing_dev_info per disk and people have
> been known to have thousands (iirc ~10,000) disks online.

8 bytes per backing device. 80000 bytes for 10000 disks.

> And those examples were plucked only from today's kernel. Who knows
> what other problems will be in 2.6.45?

We can always increase the sizes.