Re: [PATCH 19/28] locking/lockdep: Optimize irq usage check when marking lock usage bit

[Yuyang Du]

Thanks for review.

On Fri, 26 Apr 2019 at 03:32, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Wed, Apr 24, 2019 at 06:19:25PM +0800, Yuyang Du wrote:
>
> After only a quick read of these next patches; this is the one that
> worries me most.
>
> You did mention Frederic's patches, but I'm not entirely sure you're
> aware why he's doing them. He's preparing to split the softirq state
> into one state per softirq vector.
>
> See here:
>
>   https://lkml.kernel.org/r/20190228171242.32144-14-frederic@xxxxxxxxxx
>   https://lkml.kernel.org/r/20190228171242.32144-15-frederic@xxxxxxxxxx
>
> IOW he's going to massively explode this storage.

If I understand correctly, he is not going to.

First of all, we can divide the whole usage thing into tracking and checking.

Frederic's fine-grained soft vector state is applied to usage
tracking, i.e., which specific vectors a lock is used or enabled.

But for usage checking, which vectors are does not really matter. So,
the current size of the arrays and bitmaps are good enough. Right?