linux-kernel - Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

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Date:   Thu, 24 May 2018 10:35:03 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

On 05/24/2018 08:52 AM, Vlastimil Babka wrote:
> On 05/24/2018 02:13 PM, Roman Gushchin wrote:
>> On Thu, May 24, 2018 at 01:00:06PM +0200, Vlastimil Babka wrote:
>>> Hi,
>>>
>>> - I haven't find any other obvious users for reclaimable kmalloc (yet)
>>
>> As I remember, ION memory allocator was discussed related to this theme:
>> https://lkml.org/lkml/2018/4/24/1288
> 
> +CC Laura
> 
> Yeah ION added the NR_INDIRECTLY_RECLAIMABLE_BYTES handling, which is
> adjusted to page granularity in patch 4. I'm not sure if it should use
> kmalloc as it seems to be allocating order-X pages, where kmalloc/slab
> just means extra overhead. But maybe if it doesn't allocate/free too
> frequently, it could work?
> 

The page pool allocation is supposed to be a slow path but it's
one I'd rather not have too much overhead. It also just looks really odd
to be allocating higher order pages via kmalloc imho.
  
>>> I did a superset as IIRC somebody suggested that in the older threads or at LSF.
>>
>> This looks nice to me!
>>
>> Thanks!
>>
>