diff mbox series

[V4,08/11] vfio/pci: Use bitfield for struct vfio_pci_core_device flags

Message ID 42397f8cd0419694797c6c5cf65ed715117fc760.1682615447.git.reinette.chatre@intel.com
State New
Headers
Series vfio/pci: Support dynamic allocation of MSI-X interrupts |

Commit Message

Reinette Chatre April 27, 2023, 5:36 p.m. UTC 
  struct vfio_pci_core_device contains eleven boolean flags.
Boolean flags clearly indicate their usage but space usage
starts to be a concern when there are many.

An upcoming change adds another boolean flag to
struct vfio_pci_core_device, thereby increasing the concern
that the boolean flags are consuming unnecessary space.

Transition the boolean flags to use bitfields. On a system that
uses one byte per boolean this reduces the space consumed
by existing flags from 11 bytes to 2 bytes with room for
a few more flags without increasing the structure's size.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since V3:
- New patch. (Jason)

 include/linux/vfio_pci_core.h | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

Comments

Tian, Kevin April 28, 2023, 6:43 a.m. UTC | #1 
> From: Chatre, Reinette <reinette.chatre@intel.com>
> Sent: Friday, April 28, 2023 1:36 AM
> 
> struct vfio_pci_core_device contains eleven boolean flags.
> Boolean flags clearly indicate their usage but space usage
> starts to be a concern when there are many.
> 
> An upcoming change adds another boolean flag to
> struct vfio_pci_core_device, thereby increasing the concern
> that the boolean flags are consuming unnecessary space.
> 
> Transition the boolean flags to use bitfields. On a system that
> uses one byte per boolean this reduces the space consumed
> by existing flags from 11 bytes to 2 bytes with room for
> a few more flags without increasing the structure's size.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
diff mbox series

Patch

diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index 148fd1ae6c1c..adb47e2914d7 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -68,17 +68,17 @@  struct vfio_pci_core_device {
 	u16			msix_size;
 	u32			msix_offset;
 	u32			rbar[7];
-	bool			pci_2_3;
-	bool			virq_disabled;
-	bool			reset_works;
-	bool			extended_caps;
-	bool			bardirty;
-	bool			has_vga;
-	bool			needs_reset;
-	bool			nointx;
-	bool			needs_pm_restore;
-	bool			pm_intx_masked;
-	bool			pm_runtime_engaged;
+	bool			pci_2_3:1;
+	bool			virq_disabled:1;
+	bool			reset_works:1;
+	bool			extended_caps:1;
+	bool			bardirty:1;
+	bool			has_vga:1;
+	bool			needs_reset:1;
+	bool			nointx:1;
+	bool			needs_pm_restore:1;
+	bool			pm_intx_masked:1;
+	bool			pm_runtime_engaged:1;
 	struct pci_saved_state	*pci_saved_state;
 	struct pci_saved_state	*pm_save;
 	int			ioeventfds_nr;