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authorSebastian Ott <sebott@linux.vnet.ibm.com>2016-09-08 13:25:01 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2016-09-22 13:42:33 +0200
commit13954fd6913acff8f8b8c21612074b57051ba457 (patch)
tree5f2b8e7c89df80c25923fcfcdf252e24f9434ad0 /arch/s390/include/asm/pci.h
parents390/pci_dma: split dma_update_trans (diff)
downloadlinux-13954fd6913acff8f8b8c21612074b57051ba457.tar.xz
linux-13954fd6913acff8f8b8c21612074b57051ba457.zip
s390/pci_dma: improve lazy flush for unmap
Lazy unmap (defer tlb flush after unmap until dma address reuse) can greatly reduce the number of RPCIT instructions in the best case. In reality we are often far away from the best case scenario because our implementation suffers from the following problem: To create dma addresses we maintain an iommu bitmap and a pointer into that bitmap to mark the start of the next search. That pointer moves from the start to the end of that bitmap and we issue a global tlb flush once that pointer wraps around. To prevent address reuse before we issue the tlb flush we even have to move the next pointer during unmaps - when clearing a bit > next. This could lead to a situation where we only use the rear part of that bitmap and issue more tlb flushes than expected. To fix this we no longer clear bits during unmap but maintain a 2nd bitmap which we use to mark addresses that can't be reused until we issue the global tlb flush after wrap around. Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include/asm/pci.h')
-rw-r--r--arch/s390/include/asm/pci.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 8769cbf9d7cf..6611f798d2be 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -118,6 +118,7 @@ struct zpci_dev {
spinlock_t iommu_bitmap_lock;
unsigned long *iommu_bitmap;
+ unsigned long *lazy_bitmap;
unsigned long iommu_size;
unsigned long iommu_pages;
unsigned int next_bit;