linux-kernel - Re: [PATCH v3 3/3] iommu/iova: use named kmem

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Date: Tue, 6 Feb 2024 11:24:05 +0000
From: John Garry <john.g.garry@...cle.com>
To: Robin Murphy <robin.murphy@....com>, joro@...tes.org
Cc: will@...nel.org, pasha.tatashin@...een.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, rientjes@...gle.com,
        yosryahmed@...gle.com
Subject: Re: [PATCH v3 3/3] iommu/iova: use named kmem_cache for iova
 magazines

On 05/02/2024 15:32, Robin Murphy wrote:
> From: Pasha Tatashin <pasha.tatashin@...een.com>
> 
> The magazine buffers can take gigabytes of kmem memory, dominating all
> other allocations. For observability purpose create named slab cache so
> the iova magazine memory overhead can be clearly observed.
> 
> With this change:
> 
>> slabtop -o | head
>   Active / Total Objects (% used)    : 869731 / 952904 (91.3%)
>   Active / Total Slabs (% used)      : 103411 / 103974 (99.5%)
>   Active / Total Caches (% used)     : 135 / 211 (64.0%)
>   Active / Total Size (% used)       : 395389.68K / 411430.20K (96.1%)
>   Minimum / Average / Maximum Object : 0.02K / 0.43K / 8.00K
> 
> OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
> 244412 244239 99%    1.00K  61103       4    244412K iommu_iova_magazine
>   91636  88343 96%    0.03K    739     124      2956K kmalloc-32
>   75744  74844 98%    0.12K   2367      32      9468K kernfs_node_cache
> 
> On this machine it is now clear that magazine use 242M of kmem memory.

Those caches could do with a trimming ...

> 
> Acked-by: David Rientjes <rientjes@...gle.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> [ rm: adjust to rework of iova_cache_{get,put} ]
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---

FWIW:
Reviewed-by: John Garry <john.g.garry@...cle.com>