Re: [PATCH 2/3] mm: avoid slub allocation while holding list_lock

From: Yu Zhao
Date: Wed Sep 11 2019 - 21:31:08 EST

On Thu, Sep 12, 2019 at 03:44:01AM +0300, Kirill A. Shutemov wrote:
> On Wed, Sep 11, 2019 at 06:29:28PM -0600, Yu Zhao wrote:
> > If we are already under list_lock, don't call kmalloc(). Otherwise we
> > will run into deadlock because kmalloc() also tries to grab the same
> > lock.
> >
> > Instead, statically allocate bitmap in struct kmem_cache_node. Given
> > currently page->objects has 15 bits, we bloat the per-node struct by
> > 4K. So we waste some memory but only do so when slub debug is on.
> Why not have single page total protected by a lock?
> Listing object from two pages at the same time doesn't make sense anyway.
> Cuncurent validating is not something sane to do.

Okay, cutting down to static global bitmap.