linux-kernel - Re: [PATCH 08/16] iommu/fsl: use page allocation function provided by iommu-pages.h

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Message-ID: <20231129200305.GI1312390@ziepe.ca>
Date:   Wed, 29 Nov 2023 16:03:05 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     Robin Murphy <robin.murphy@....com>, akpm@...ux-foundation.org,
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Subject: Re: [PATCH 08/16] iommu/fsl: use page allocation function provided
 by iommu-pages.h

On Wed, Nov 29, 2023 at 02:45:03PM -0500, Pasha Tatashin wrote:

> > same kind of big systems where IOMMU pagetables would be of any concern.
> > I believe some of the some of the "serious" NICs can easily run up
> > hundreds of megabytes if not gigabytes worth of queues, SKB pools, etc.
> > - would you propose accounting those too?
> 
> Yes. Any kind of kernel memory that is proportional to the workload
> should be accountable. Someone is using those resources compared to
> the idling system, and that someone should be charged.

There is a difference between charged and accounted

You should be running around adding GFP_KERNEL_ACCOUNT, yes. I already
did a bunch of that work. Split that out from this series and send it
to the right maintainers.

Adding a counter for allocations and showing in procfs is a very
different question. IMHO that should not be done in micro, the
threshold to add a new counter should be high.

There is definately room for a generic debugging feature to break down
GFP_KERNEL_ACCOUNT by owernship somehow. Maybe it can already be done
with BPF. IDK

Jason