linux-kernel - Re: [PATCH 0/4] mm: Use slab_list list

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Message-ID: <20190311204919.GA20002@tower.DHCP.thefacebook.com>
Date:   Mon, 11 Mar 2019 20:49:23 +0000
From:   Roman Gushchin <guro@...com>
To:     "Tobin C. Harding" <tobin@...nel.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] mm: Use slab_list list_head instead of lru

On Mon, Mar 11, 2019 at 12:07:40PM +1100, Tobin C. Harding wrote:
> Currently the slab allocators (ab)use the struct page 'lru' list_head.
> We have a list head for slab allocators to use, 'slab_list'.
> 
> Clean up all three allocators by using the 'slab_list' list_head instead
> of overloading the 'lru' list_head.
> 
> Initial patch makes no code changes, adds comments to #endif statements.
> 
> Final 3 patches do changes as a patch per allocator, tested by building
> and booting (in Qemu) after configuring kernel to use appropriate
> allocator.  Also build and boot with debug options enabled (for slab
> and slub).

Hi Tobin!

The patchset looks good to me, however I'd add some clarifications
why switching from lru to slab_list is safe.

My understanding is that the slab_list fields isn't currently in use,
but it's not that obvious that putting slab_list and next/pages/pobjects
fields into a union is safe (for the slub case).

Please, add a clarification/comment.

For patches 1, 3 and 4:
Reviewed-by: Roman Gushchin <guro@...com>

Thanks!