Messages in this thread | | | Date | Mon, 2 Aug 2021 16:01:53 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v4 2/6] iova: Allow rcache range upper limit to be flexible |
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On Wed, Jul 14, 2021 at 06:36:39PM +0800, John Garry wrote: > Some LLDs may request DMA mappings whose IOVA length exceeds that of the > current rcache upper limit.
What's an LLD?
> This means that allocations for those IOVAs will never be cached, and > always must be allocated and freed from the RB tree per DMA mapping cycle. > This has a significant effect on performance, more so since commit > 4e89dce72521 ("iommu/iova: Retry from last rb tree node if iova search > fails"), as discussed at [0]. > > As a first step towards allowing the rcache range upper limit be > configured, hold this value in the IOVA rcache structure, and allocate > the rcaches separately. > > [0] https://lore.kernel.org/linux-iommu/20210129092120.1482-1-thunder.leizhen@huawei.com/ > > Signed-off-by: John Garry <john.garry@huawei.com> > --- > drivers/iommu/dma-iommu.c | 2 +- > drivers/iommu/iova.c | 23 +++++++++++++++++------ > include/linux/iova.h | 4 ++-- > 3 files changed, 20 insertions(+), 9 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 98ba927aee1a..4772278aa5da 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -434,7 +434,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, > * rounding up anything cacheable to make sure that can't happen. The > * order of the unadjusted size will still match upon freeing. > */ > - if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1))) > + if (iova_len < (1 << (iovad->rcache_max_size - 1))) > iova_len = roundup_pow_of_two(iova_len); > > dma_limit = min_not_zero(dma_limit, dev->bus_dma_limit); > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index b6cf5f16123b..07ce73fdd8c1 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -15,6 +15,8 @@ > /* The anchor node sits above the top of the usable address space */ > #define IOVA_ANCHOR ~0UL > > +#define IOVA_RANGE_CACHE_MAX_SIZE 6 /* log of max cached IOVA range size (in pages) */
Is that the same as an 'order'? i.e. IOVA_RANGE_CACHE_MAX_ORDER?
> + > static bool iova_rcache_insert(struct iova_domain *iovad, > unsigned long pfn, > unsigned long size); > @@ -881,7 +883,14 @@ static void init_iova_rcaches(struct iova_domain *iovad) > unsigned int cpu; > int i; > > - for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { > + iovad->rcache_max_size = IOVA_RANGE_CACHE_MAX_SIZE; > + > + iovad->rcaches = kcalloc(iovad->rcache_max_size, > + sizeof(*iovad->rcaches), GFP_KERNEL); > + if (!iovad->rcaches) > + return;
Returning quietly here doesn't seem like the right thing to do. At least, I don't think the rest of the functions here are checking rcaches against NULL.
Will
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