From 159ef31e81edd75225c6a844115faf999de67b38 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 26 Feb 2019 15:32:29 +0100 Subject: device.h: reorganize struct device struct device is big, around 760 bytes on x86_64. It's not a critical structure, but it is embedded everywhere, so making it smaller is always a good thing. With a recent patch that moved a field from struct device to the private structure, some benchmarks showed a very odd regression, despite this structure having nothing to do with those benchmarks. That caused me to look into the layout of the structure. Using 'pahole', it showed a number of holes and ways that the structure could be reordered in order to align some cachelines better, as well as reduce the size of the overall structure. Move 'struct kobj' to the start of the structure, to keep that access in the first cacheline, and try to organize things a bit more compactly where possible By doing these few moves, the result removes at least 8 bytes from 'struct device' on a 64bit system. Given we know there are systems with at least 30k devices in memory at once, every little byte counts, and this change could be a savings of 240k of kernel memory for them. On "normal" systems the overall memory savings would be much less. Cc: "Rafael J. Wysocki" Cc: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- include/linux/device.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'include/linux/device.h') diff --git a/include/linux/device.h b/include/linux/device.h index 4e6987e11f68..4457e560bc2b 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -976,18 +976,14 @@ struct dev_links_info { * a higher-level representation of the device. */ struct device { + struct kobject kobj; struct device *parent; struct device_private *p; - struct kobject kobj; const char *init_name; /* initial name of the device */ const struct device_type *type; - struct mutex mutex; /* mutex to synchronize calls to - * its driver. - */ - struct bus_type *bus; /* type of bus device is on */ struct device_driver *driver; /* which driver has allocated this device */ @@ -995,6 +991,10 @@ struct device { core doesn't touch it */ void *driver_data; /* Driver data, set and get with dev_set_drvdata/dev_get_drvdata */ + struct mutex mutex; /* mutex to synchronize calls to + * its driver. + */ + struct dev_links_info links; struct dev_pm_info power; struct dev_pm_domain *pm_domain; @@ -1009,9 +1009,6 @@ struct device { struct list_head msi_list; #endif -#ifdef CONFIG_NUMA - int numa_node; /* NUMA node this device is close to */ -#endif const struct dma_map_ops *dma_ops; u64 *dma_mask; /* dma mask (if dma'able device) */ u64 coherent_dma_mask;/* Like dma_mask, but for @@ -1040,6 +1037,9 @@ struct device { struct device_node *of_node; /* associated device tree node */ struct fwnode_handle *fwnode; /* firmware device node */ +#ifdef CONFIG_NUMA + int numa_node; /* NUMA node this device is close to */ +#endif dev_t devt; /* dev_t, creates the sysfs "dev" */ u32 id; /* device instance */ -- cgit v1.2.3 From 1b833924e5b3cea92306069a0f366529341dd260 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Fri, 12 Apr 2019 11:31:45 -0700 Subject: driver core: Let dev_of_node() accept a NULL dev We'd like to chain this in places where the 'dev' argument might be NULL. Let this function take a NULL 'dev' so this can work. Cc: Miquel Raynal Cc: Jerome Brunet Cc: Russell King Cc: Michael Turquette Cc: Jeffrey Hugo Cc: Chen-Yu Tsai Cc: Greg Kroah-Hartman Cc: Rob Herring Acked-by: Greg Kroah-Hartman Tested-by: Jeffrey Hugo Signed-off-by: Stephen Boyd --- include/linux/device.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/device.h') diff --git a/include/linux/device.h b/include/linux/device.h index b425a7ee04ce..0370dd0b3ae7 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -1231,7 +1231,7 @@ static inline void device_lock_assert(struct device *dev) static inline struct device_node *dev_of_node(struct device *dev) { - if (!IS_ENABLED(CONFIG_OF)) + if (!IS_ENABLED(CONFIG_OF) || !dev) return NULL; return dev->of_node; } -- cgit v1.2.3