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linux-next/drivers/of/of_private.h
Rob Herring 90dc0d1ce8 of: Rework and simplify phandle cache to use a fixed size 
The phandle cache was added to speed up of_find_node_by_phandle() by
avoiding walking the whole DT to find a matching phandle. The
implementation has several shortcomings:

  - The cache is designed to work on a linear set of phandle values.
    This is true for dtc generated DTs, but not for other cases such as
    Power.
  - The cache isn't enabled until of_core_init() and a typical system
    may see hundreds of calls to of_find_node_by_phandle() before that
    point.
  - The cache is freed and re-allocated when the number of phandles
    changes.
  - It takes a raw spinlock around a memory allocation which breaks on
    RT.

Change the implementation to a fixed size and use hash_32() as the
cache index. This greatly simplifies the implementation. It avoids
the need for any re-alloc of the cache and taking a reference on nodes
in the cache. We only have a single source of removing cache entries
which is of_detach_node().

Using hash_32() removes any assumption on phandle values improving
the hit rate for non-linear phandle values. The effect on linear values
using hash_32() is about a 10% collision. The chances of thrashing on
colliding values seems to be low.

To compare performance, I used a RK3399 board which is a pretty typical
system. I found that just measuring boot time as done previously is
noisy and may be impacted by other things. Also bringing up secondary
cores causes some issues with measuring, so I booted with 'nr_cpus=1'.
With no caching, calls to of_find_node_by_phandle() take about 20124 us
for 1248 calls. There's an additional 288 calls before time keeping is
up. Using the average time per hit/miss with the cache, we can calculate
these calls to take 690 us (277 hit / 11 miss) with a 128 entry cache
and 13319 us with no cache or an uninitialized cache.

Comparing the 3 implementations the time spent in
of_find_node_by_phandle() is:

no cache:        20124 us (+ 13319 us)
128 entry cache:  5134 us (+ 690 us)
current cache:     819 us (+ 13319 us)

We could move the allocation of the cache earlier to improve the
current cache, but that just further complicates the situation as it
needs to be after slab is up, so we can't do it when unflattening (which
uses memblock).

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Frank Rowand <frowand.list@gmail.com>
Tested-by: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>
2019-12-24 14:17:52 -07:00

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/* SPDX-License-Identifier: GPL-2.0+ */
#ifndef _LINUX_OF_PRIVATE_H
#define _LINUX_OF_PRIVATE_H
/*
* Private symbols used by OF support code
*
* Paul Mackerras August 1996.
* Copyright (C) 1996-2005 Paul Mackerras.
*/
/**
* struct alias_prop - Alias property in 'aliases' node
* @link: List node to link the structure in aliases_lookup list
* @alias: Alias property name
* @np: Pointer to device_node that the alias stands for
* @id: Index value from end of alias name
* @stem: Alias string without the index
*
* The structure represents one alias property of 'aliases' node as
* an entry in aliases_lookup list.
*/
struct alias_prop {
struct list_head link;
const char *alias;
struct device_node *np;
int id;
char stem[0];
};
#if defined(CONFIG_SPARC)
#define OF_ROOT_NODE_ADDR_CELLS_DEFAULT 2
#else
#define OF_ROOT_NODE_ADDR_CELLS_DEFAULT 1
#endif
#define OF_ROOT_NODE_SIZE_CELLS_DEFAULT 1
extern struct mutex of_mutex;
extern struct list_head aliases_lookup;
extern struct kset *of_kset;
#if defined(CONFIG_OF_DYNAMIC)
extern int of_property_notify(int action, struct device_node *np,
struct property *prop, struct property *old_prop);
extern void of_node_release(struct kobject *kobj);
extern int __of_changeset_apply_entries(struct of_changeset *ocs,
int *ret_revert);
extern int __of_changeset_apply_notify(struct of_changeset *ocs);
extern int __of_changeset_revert_entries(struct of_changeset *ocs,
int *ret_apply);
extern int __of_changeset_revert_notify(struct of_changeset *ocs);
#else /* CONFIG_OF_DYNAMIC */
static inline int of_property_notify(int action, struct device_node *np,
struct property *prop, struct property *old_prop)
{
return 0;
}
#endif /* CONFIG_OF_DYNAMIC */
#if defined(CONFIG_OF_KOBJ)
int of_node_is_attached(struct device_node *node);
int __of_add_property_sysfs(struct device_node *np, struct property *pp);
void __of_remove_property_sysfs(struct device_node *np, struct property *prop);
void __of_update_property_sysfs(struct device_node *np, struct property *newprop,
struct property *oldprop);
int __of_attach_node_sysfs(struct device_node *np);
void __of_detach_node_sysfs(struct device_node *np);
#else
static inline int __of_add_property_sysfs(struct device_node *np, struct property *pp)
{
return 0;
}
static inline void __of_remove_property_sysfs(struct device_node *np, struct property *prop) {}
static inline void __of_update_property_sysfs(struct device_node *np,
struct property *newprop, struct property *oldprop) {}
static inline int __of_attach_node_sysfs(struct device_node *np)
{
return 0;
}
static inline void __of_detach_node_sysfs(struct device_node *np) {}
#endif
#if defined(CONFIG_OF_RESOLVE)
int of_resolve_phandles(struct device_node *tree);
#endif
void __of_phandle_cache_inv_entry(phandle handle);
#if defined(CONFIG_OF_OVERLAY)
void of_overlay_mutex_lock(void);
void of_overlay_mutex_unlock(void);
#else
static inline void of_overlay_mutex_lock(void) {};
static inline void of_overlay_mutex_unlock(void) {};
#endif
#if defined(CONFIG_OF_UNITTEST) && defined(CONFIG_OF_OVERLAY)
extern void __init unittest_unflatten_overlay_base(void);
#else
static inline void unittest_unflatten_overlay_base(void) {};
#endif
extern void *__unflatten_device_tree(const void *blob,
struct device_node *dad,
struct device_node **mynodes,
void *(*dt_alloc)(u64 size, u64 align),
bool detached);
/**
* General utilities for working with live trees.
*
* All functions with two leading underscores operate
* without taking node references, so you either have to
* own the devtree lock or work on detached trees only.
*/
struct property *__of_prop_dup(const struct property *prop, gfp_t allocflags);
struct device_node *__of_node_dup(const struct device_node *np,
const char *full_name);
struct device_node *__of_find_node_by_path(struct device_node *parent,
const char *path);
struct device_node *__of_find_node_by_full_path(struct device_node *node,
const char *path);
extern const void *__of_get_property(const struct device_node *np,
const char *name, int *lenp);
extern int __of_add_property(struct device_node *np, struct property *prop);
extern int __of_add_property_sysfs(struct device_node *np,
struct property *prop);
extern int __of_remove_property(struct device_node *np, struct property *prop);
extern void __of_remove_property_sysfs(struct device_node *np,
struct property *prop);
extern int __of_update_property(struct device_node *np,
struct property *newprop, struct property **oldprop);
extern void __of_update_property_sysfs(struct device_node *np,
struct property *newprop, struct property *oldprop);
extern int __of_attach_node_sysfs(struct device_node *np);
extern void __of_detach_node(struct device_node *np);
extern void __of_detach_node_sysfs(struct device_node *np);
extern void __of_sysfs_remove_bin_file(struct device_node *np,
struct property *prop);
/* illegal phandle value (set when unresolved) */
#define OF_PHANDLE_ILLEGAL 0xdeadbeef
/* iterators for transactions, used for overlays */
/* forward iterator */
#define for_each_transaction_entry(_oft, _te) \
list_for_each_entry(_te, &(_oft)->te_list, node)
/* reverse iterator */
#define for_each_transaction_entry_reverse(_oft, _te) \
list_for_each_entry_reverse(_te, &(_oft)->te_list, node)
extern int of_bus_n_addr_cells(struct device_node *np);
extern int of_bus_n_size_cells(struct device_node *np);
#ifdef CONFIG_OF_ADDRESS
extern int of_dma_get_range(struct device_node *np, u64 *dma_addr,
u64 *paddr, u64 *size);
#else
static inline int of_dma_get_range(struct device_node *np, u64 *dma_addr,
u64 *paddr, u64 *size)
{
return -ENODEV;
}
#endif
#endif /* _LINUX_OF_PRIVATE_H */
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