On Mon, Oct 30, 2017 at 9:33 PM, Bart Van Assche [off-list ref] wrote:

On Fri, 2017-10-27 at 19:55 +0200, Roman Penyaev wrote:

quoted

That's just a bug in code, not a in issue with restarts, which can be fixed
if we put hctx which are needed to be restarted in percpu lists and avoid
long loops and contentions.

Hello Roman,

Have you noticed that recently .get_budget() and .put_budget() callbacks have
been added into struct blk_mq_ops? If block drivers that support shared tags
implement these callback functions properly then maybe busy conditions become
infrequent enough to use a single "hctx busy" list per tag set instead of
per-cpu "hctx busy" lists.

Hi Bart,

No, not yet.  Thanks, good tip.

--
Roman