Re: 4.4-final: 28 bioset threads on small notebook

[Ming Lei]

On Tue, Feb 23, 2016 at 6:58 AM, Kent Overstreet
<kent.overstreet@xxxxxxxxx> wrote:
> On Sun, Feb 21, 2016 at 05:40:59PM +0800, Ming Lei wrote:
>> On Sun, Feb 21, 2016 at 2:43 PM, Ming Lin-SSI <ming.l@xxxxxxxxxxxxxxx> wrote:
>> >>-----Original Message-----
>> >
>> > So it's almost already "per request_queue"
>>
>> Yes, that is because of the following line:
>>
>> q->bio_split = bioset_create(BIO_POOL_SIZE, 0);
>>
>> in blk_alloc_queue_node().
>>
>> Looks like this bio_set doesn't need to be per-request_queue, and
>> now it is only used for fast-cloning bio for splitting, and one global
>> split bio_set should be enough.
>
> It does have to be per request queue for stacking block devices (which includes
> loopback).

In commit df2cb6daa4(block: Avoid deadlocks with bio allocation by
stacking drivers), deadlock in this situation has been avoided already.
Or are there other issues with global bio_set? I appreciate if you may
explain it a bit if there are.

Thanks,
Ming Lei