From mboxrd@z Thu Jan 1 00:00:00 1970 From: manoj.iyer@canonical.com (Manoj Iyer) Date: Thu, 6 Apr 2017 13:15:37 -0500 (CDT) Subject: [RESEND,3/3] iommu/dma: Plumb in the per-CPU IOVA caches In-Reply-To: References: Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 31 Mar 2017, Robin Murphy wrote: > With IOVA allocation suitably tidied up, we are finally free to opt in > to the per-CPU caching mechanism. The caching alone can provide a modest > improvement over walking the rbtree for weedier systems (iperf3 shows > ~10% more ethernet throughput on an ARM Juno r1 constrained to a single > 650MHz Cortex-A53), but the real gain will be in sidestepping the rbtree > lock contention which larger ARM-based systems with lots of parallel I/O > are starting to feel the pain of. > > Reviewed-by: Nate Watterson > Tested-by: Nate Watterson > Signed-off-by: Robin Murphy > --- > drivers/iommu/dma-iommu.c | 39 ++++++++++++++++++--------------------- > 1 file changed, 18 insertions(+), 21 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 1b94beb43036..8348f366ddd1 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -361,8 +361,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, > { > struct iommu_dma_cookie *cookie = domain->iova_cookie; > struct iova_domain *iovad = &cookie->iovad; > - unsigned long shift, iova_len; > - struct iova *iova = NULL; > + unsigned long shift, iova_len, iova = 0; > > if (cookie->type == IOMMU_DMA_MSI_COOKIE) { > cookie->msi_iova += size; > @@ -371,41 +370,39 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, > > shift = iova_shift(iovad); > iova_len = size >> shift; > + /* > + * Freeing non-power-of-two-sized allocations back into the IOVA caches > + * will come back to bite us badly, so we have to waste a bit of space > + * 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))) > + iova_len = roundup_pow_of_two(iova_len); > > if (domain->geometry.force_aperture) > dma_limit = min(dma_limit, domain->geometry.aperture_end); > > /* Try to get PCI devices a SAC address */ > if (dma_limit > DMA_BIT_MASK(32) && dev_is_pci(dev)) > - iova = alloc_iova(iovad, iova_len, DMA_BIT_MASK(32) >> shift, > - true); > - /* > - * Enforce size-alignment to be safe - there could perhaps be an > - * attribute to control this per-device, or at least per-domain... > - */ > - if (!iova) > - iova = alloc_iova(iovad, iova_len, dma_limit >> shift, true); > + iova = alloc_iova_fast(iovad, iova_len, DMA_BIT_MASK(32) >> shift); > > - return (dma_addr_t)iova->pfn_lo << shift; > + if (!iova) > + iova = alloc_iova_fast(iovad, iova_len, dma_limit >> shift); > + > + return (dma_addr_t)iova << shift; > } > > static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie, > dma_addr_t iova, size_t size) > { > struct iova_domain *iovad = &cookie->iovad; > - struct iova *iova_rbnode; > + unsigned long shift = iova_shift(iovad); > > /* The MSI case is only ever cleaning up its most recent allocation */ > - if (cookie->type == IOMMU_DMA_MSI_COOKIE) { > + if (cookie->type == IOMMU_DMA_MSI_COOKIE) > cookie->msi_iova -= size; > - return; > - } > - > - iova_rbnode = find_iova(iovad, iova_pfn(iovad, iova)); > - if (WARN_ON(!iova_rbnode)) > - return; > - > - __free_iova(iovad, iova_rbnode); > + else > + free_iova_fast(iovad, iova >> shift, size >> shift); > } > > static void __iommu_dma_unmap(struct iommu_domain *domain, dma_addr_t dma_addr, > This patch series helps to resolve the Ubuntu bug, where we see the Ubuntu Zesty (4.10 based) kernel reporting multi cpu soft lockups on QDF2400 SDP. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1680549 This patch series along with the following cherry-picks from Linus's tree dddd632b072f iommu/dma: Implement PCI allocation optimisation de84f5f049d9 iommu/dma: Stop getting dma_32bit_pfn wrong were applied to Ubuntu Zesty 4.10 kernel (Ubuntu-4.10.0-18.20) and tested on a QDF2400 SDP. Tested-by: Manoj Iyer -- ============================ Manoj Iyer Ubuntu/Canonical ARM Servers - Cloud ============================