Hi Robin, On Thu, Aug 9, 2018 at 9:54 PM, Robin Murphy <robin.mur...@arm.com> wrote: > On 07/08/18 09:54, Ganapatrao Kulkarni wrote: >> >> As an optimisation for PCI devices, there is always first attempt >> been made to allocate iova from SAC address range. This will lead >> to unnecessary attempts/function calls, when there are no free ranges >> available. >> >> This patch optimises by adding flag to track previous failed attempts >> and avoids further attempts until replenish happens. > > > Agh, what I overlooked is that this still suffers from the original problem, > wherein a large allocation which fails due to fragmentation then blocks all > subsequent smaller allocations, even if they may have succeeded. > > For a minimal change, though, what I think we could do is instead of just > having a flag, track the size of the last 32-bit allocation which failed. If > we're happy to assume that nobody's likely to mix aligned and unaligned > allocations within the same domain, then that should be sufficiently robust > whilst being no more complicated than this version, i.e. (modulo thinking up > a better name for it):
I agree, it would be better to track size and attempt to allocate for smaller chunks, if not for bigger one. > >> >> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> >> --- >> This patch is based on comments from Robin Murphy <robin.mur...@arm.com> >> for patch [1] >> >> [1] https://lkml.org/lkml/2018/4/19/780 >> >> drivers/iommu/iova.c | 11 ++++++++++- >> include/linux/iova.h | 1 + >> 2 files changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c >> index 83fe262..d97bb5a 100644 >> --- a/drivers/iommu/iova.c >> +++ b/drivers/iommu/iova.c >> @@ -56,6 +56,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned >> long granule, >> iovad->granule = granule; >> iovad->start_pfn = start_pfn; >> iovad->dma_32bit_pfn = 1UL << (32 - iova_shift(iovad)); >> + iovad->free_32bit_pfns = true; > > > iovad->max_32bit_free = iovad->dma_32bit_pfn; > >> iovad->flush_cb = NULL; >> iovad->fq = NULL; >> iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR; >> @@ -139,8 +140,10 @@ __cached_rbnode_delete_update(struct iova_domain >> *iovad, struct iova *free) >> cached_iova = rb_entry(iovad->cached32_node, struct iova, node); >> if (free->pfn_hi < iovad->dma_32bit_pfn && >> - free->pfn_lo >= cached_iova->pfn_lo) >> + free->pfn_lo >= cached_iova->pfn_lo) { >> iovad->cached32_node = rb_next(&free->node); >> + iovad->free_32bit_pfns = true; > > > iovad->max_32bit_free = iovad->dma_32bit_pfn; i think, you intended to say, iovad->max_32bit_free += (free->pfn_hi - free->pfn_lo); > >> + } >> cached_iova = rb_entry(iovad->cached_node, struct iova, node); >> if (free->pfn_lo >= cached_iova->pfn_lo) >> @@ -290,6 +293,10 @@ alloc_iova(struct iova_domain *iovad, unsigned long >> size, >> struct iova *new_iova; >> int ret; >> + if (limit_pfn <= iovad->dma_32bit_pfn && >> + !iovad->free_32bit_pfns) > > > size >= iovad->max_32bit_free) > >> + return NULL; >> + >> new_iova = alloc_iova_mem(); >> if (!new_iova) >> return NULL; >> @@ -299,6 +306,8 @@ alloc_iova(struct iova_domain *iovad, unsigned long >> size, >> if (ret) { >> free_iova_mem(new_iova); >> + if (limit_pfn <= iovad->dma_32bit_pfn) >> + iovad->free_32bit_pfns = false; > > > iovad->max_32bit_free = size; same here, we should decrease available free range after successful allocation. iovad->max_32bit_free -= size; > > What do you think? most likely this should work, i will try this and confirm at the earliest, > > Robin. > > >> return NULL; >> } >> diff --git a/include/linux/iova.h b/include/linux/iova.h >> index 928442d..3810ba9 100644 >> --- a/include/linux/iova.h >> +++ b/include/linux/iova.h >> @@ -96,6 +96,7 @@ struct iova_domain { >> flush-queues */ >> atomic_t fq_timer_on; /* 1 when timer is active, >> 0 >> when not */ >> + bool free_32bit_pfns; >> }; >> static inline unsigned long iova_size(struct iova *iova) >> > thanks, Ganapat _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
