From: Pasha Tatashin <pasha.tatashin@soleen.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: akpm@linux-foundation.org, alim.akhtar@samsung.com,
alyssa@rosenzweig.io, asahi@lists.linux.dev,
baolu.lu@linux.intel.com, bhelgaas@google.com,
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tomas.mudrunka@gmail.com, vdumpa@nvidia.com, wens@csie.org,
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Subject: Re: [PATCH v4 01/10] iommu/vt-d: add wrapper functions for page allocations
Date: Thu, 15 Feb 2024 20:05:55 -0500 [thread overview]
Message-ID: <CA+CK2bBTe93nXzY3Qhty+821LrkjBVnQDxro3m7Y-GVihSP18A@mail.gmail.com> (raw)
In-Reply-To: <b008bd2d-a189-481f-917d-bb045c43cb07@arm.com>
> >>> + */
> >>> +static inline void *iommu_alloc_page_node(int nid, gfp_t gfp)
> >>> +{
> >>> + return iommu_alloc_pages_node(nid, gfp, 0);
> >>> +}
> >>
> >> TBH I'm not entirely convinced that saving 4 characters per invocation
> >> times 11 invocations makes this wrapper worthwhile :/
> >
> > Let's keep them. After the clean-up that you suggested, there are
> > fewer functions left in this file, but I think that it is cleaner to
> > keep these remaining, as it is beneficial to easily distinguish when
> > exactly one page is allocated vs when multiple are allocated via code
> > search.
>
> But is it, really? It's not at all obvious to me *why* it would be
> significantly interesting to distinguish fixed order-0 allocations from
> higher-order or variable-order (which may still be 0) ones. After all,
> there's no regular alloc_page_node() wrapper, yet plenty more callers of
> alloc_pages_node(..., 0) :/
The pages that are allocated with order > 0 cannot be freed using
iommu_put_pages_list(), without messing up refcounts in the tail
pages. I think having a dedicated function that guarantees order = 0
pages allocation makes it easier for the reviewer to follow the code,
and ensures that only these pages are put on the freelist.
Even in the existing code, the order=0 allocation is wrapped in the
*alloc_pgtable_page() function.
Pasha
>
> Thanks,
> Robin.
next prev parent reply other threads:[~2024-02-16 1:06 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-07 17:40 [PATCH v4 00/10] IOMMU memory observability Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 01/10] iommu/vt-d: add wrapper functions for page allocations Pasha Tatashin
2024-02-09 13:44 ` Robin Murphy
2024-02-10 2:21 ` Pasha Tatashin
2024-02-13 17:26 ` Robin Murphy
2024-02-16 1:05 ` Pasha Tatashin [this message]
2024-02-07 17:40 ` [PATCH v4 02/10] iommu/amd: use page allocation function provided by iommu-pages.h Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 03/10] iommu/io-pgtable-arm: " Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 04/10] iommu/io-pgtable-dart: " Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 05/10] iommu/exynos: " Pasha Tatashin
2024-02-09 11:26 ` Marek Szyprowski
2024-02-09 19:00 ` Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 06/10] iommu/rockchip: " Pasha Tatashin
2024-02-07 17:40 ` [PATCH v4 07/10] iommu/sun50i: " Pasha Tatashin
2024-02-09 10:55 ` Jernej Škrabec
2024-02-09 19:01 ` Pasha Tatashin
2024-02-07 17:41 ` [PATCH v4 08/10] iommu/tegra-smmu: " Pasha Tatashin
2024-02-07 17:41 ` [PATCH v4 09/10] iommu: observability of the IOMMU allocations Pasha Tatashin
2024-02-09 11:17 ` Robin Murphy
2024-02-07 17:41 ` [PATCH v4 10/10] iommu: account IOMMU allocated memory Pasha Tatashin
2024-02-09 10:50 ` [PATCH v4 00/10] IOMMU memory observability Joerg Roedel
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