linux-kernel - Re: [PATCH v2] iommu/iova: use named kmem

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Message-ID: <d506a467-8af7-dc26-709a-ba49e6c5a3a6@google.com>
Date: Fri, 2 Feb 2024 18:30:19 -0800 (PST)
From: David Rientjes <rientjes@...gle.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
cc: robin.murphy@....com, joro@...tes.org, will@...nel.org, 
    iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
    yosryahmed@...gle.com
Subject: Re: [PATCH v2] iommu/iova: use named kmem_cache for iova magazines

On Fri, 2 Feb 2024, Pasha Tatashin wrote:

> 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.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>

Very impressive!

Acked-by: David Rientjes <rientjes@...gle.com>