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Message-ID: <20090610221635.GA25816@elte.hu>
Date: Thu, 11 Jun 2009 00:16:35 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] core/percpu for v2.6.31
Linus,
Please pull the latest percpu-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git percpu-for-linus
Two leftover straightforward dynamic percpu allocator changes
(cleanup+speedup) affecting x86.
Tejun is carrying the remaining percpu patches (which affect other
architectures).
Thanks,
Ingo
------------------>
Christoph Lameter (1):
percpu: remove rbtree and use page->index instead
Tejun Heo (1):
percpu: don't put the first chunk in reverse-map rbtree
mm/percpu.c | 141 ++++++++++++++++++----------------------------------------
1 files changed, 44 insertions(+), 97 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c
index 1aa5d8f..c0b2c1a 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -23,7 +23,7 @@
* Allocation is done in offset-size areas of single unit space. Ie,
* an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
* c1:u1, c1:u2 and c1:u3. Percpu access can be done by configuring
- * percpu base registers UNIT_SIZE apart.
+ * percpu base registers pcpu_unit_size apart.
*
* There are usually many small percpu allocations many of them as
* small as 4 bytes. The allocator organizes chunks into lists
@@ -38,8 +38,8 @@
* region and negative allocated. Allocation inside a chunk is done
* by scanning this map sequentially and serving the first matching
* entry. This is mostly copied from the percpu_modalloc() allocator.
- * Chunks are also linked into a rb tree to ease address to chunk
- * mapping during free.
+ * Chunks can be determined from the address using the index field
+ * in the page struct. The index field contains a pointer to the chunk.
*
* To use this allocator, arch code should do the followings.
*
@@ -61,7 +61,6 @@
#include <linux/mutex.h>
#include <linux/percpu.h>
#include <linux/pfn.h>
-#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
@@ -88,7 +87,6 @@
struct pcpu_chunk {
struct list_head list; /* linked to pcpu_slot lists */
- struct rb_node rb_node; /* key is chunk->vm->addr */
int free_size; /* free bytes in the chunk */
int contig_hint; /* max contiguous size hint */
struct vm_struct *vm; /* mapped vmalloc region */
@@ -110,9 +108,21 @@ static size_t pcpu_chunk_struct_size __read_mostly;
void *pcpu_base_addr __read_mostly;
EXPORT_SYMBOL_GPL(pcpu_base_addr);
-/* optional reserved chunk, only accessible for reserved allocations */
+/*
+ * The first chunk which always exists. Note that unlike other
+ * chunks, this one can be allocated and mapped in several different
+ * ways and thus often doesn't live in the vmalloc area.
+ */
+static struct pcpu_chunk *pcpu_first_chunk;
+
+/*
+ * Optional reserved chunk. This chunk reserves part of the first
+ * chunk and serves it for reserved allocations. The amount of
+ * reserved offset is in pcpu_reserved_chunk_limit. When reserved
+ * area doesn't exist, the following variables contain NULL and 0
+ * respectively.
+ */
static struct pcpu_chunk *pcpu_reserved_chunk;
-/* offset limit of the reserved chunk */
static int pcpu_reserved_chunk_limit;
/*
@@ -121,7 +131,7 @@ static int pcpu_reserved_chunk_limit;
* There are two locks - pcpu_alloc_mutex and pcpu_lock. The former
* protects allocation/reclaim paths, chunks and chunk->page arrays.
* The latter is a spinlock and protects the index data structures -
- * chunk slots, rbtree, chunks and area maps in chunks.
+ * chunk slots, chunks and area maps in chunks.
*
* During allocation, pcpu_alloc_mutex is kept locked all the time and
* pcpu_lock is grabbed and released as necessary. All actual memory
@@ -140,7 +150,6 @@ static DEFINE_MUTEX(pcpu_alloc_mutex); /* protects whole alloc and reclaim */
static DEFINE_SPINLOCK(pcpu_lock); /* protects index data structures */
static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
-static struct rb_root pcpu_addr_root = RB_ROOT; /* chunks by address */
/* reclaim work to release fully free chunks, scheduled from free path */
static void pcpu_reclaim(struct work_struct *work);
@@ -191,6 +200,18 @@ static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
}
+/* set the pointer to a chunk in a page struct */
+static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
+{
+ page->index = (unsigned long)pcpu;
+}
+
+/* obtain pointer to a chunk from a page struct */
+static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
+{
+ return (struct pcpu_chunk *)page->index;
+}
+
/**
* pcpu_mem_alloc - allocate memory
* @size: bytes to allocate
@@ -257,93 +278,26 @@ static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
}
}
-static struct rb_node **pcpu_chunk_rb_search(void *addr,
- struct rb_node **parentp)
-{
- struct rb_node **p = &pcpu_addr_root.rb_node;
- struct rb_node *parent = NULL;
- struct pcpu_chunk *chunk;
-
- while (*p) {
- parent = *p;
- chunk = rb_entry(parent, struct pcpu_chunk, rb_node);
-
- if (addr < chunk->vm->addr)
- p = &(*p)->rb_left;
- else if (addr > chunk->vm->addr)
- p = &(*p)->rb_right;
- else
- break;
- }
-
- if (parentp)
- *parentp = parent;
- return p;
-}
-
/**
- * pcpu_chunk_addr_search - search for chunk containing specified address
- * @addr: address to search for
- *
- * Look for chunk which might contain @addr. More specifically, it
- * searchs for the chunk with the highest start address which isn't
- * beyond @addr.
- *
- * CONTEXT:
- * pcpu_lock.
+ * pcpu_chunk_addr_search - determine chunk containing specified address
+ * @addr: address for which the chunk needs to be determined.
*
* RETURNS:
* The address of the found chunk.
*/
static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
{
- struct rb_node *n, *parent;
- struct pcpu_chunk *chunk;
+ void *first_start = pcpu_first_chunk->vm->addr;
- /* is it in the reserved chunk? */
- if (pcpu_reserved_chunk) {
- void *start = pcpu_reserved_chunk->vm->addr;
-
- if (addr >= start && addr < start + pcpu_reserved_chunk_limit)
+ /* is it in the first chunk? */
+ if (addr >= first_start && addr < first_start + pcpu_chunk_size) {
+ /* is it in the reserved area? */
+ if (addr < first_start + pcpu_reserved_chunk_limit)
return pcpu_reserved_chunk;
+ return pcpu_first_chunk;
}
- /* nah... search the regular ones */
- n = *pcpu_chunk_rb_search(addr, &parent);
- if (!n) {
- /* no exactly matching chunk, the parent is the closest */
- n = parent;
- BUG_ON(!n);
- }
- chunk = rb_entry(n, struct pcpu_chunk, rb_node);
-
- if (addr < chunk->vm->addr) {
- /* the parent was the next one, look for the previous one */
- n = rb_prev(n);
- BUG_ON(!n);
- chunk = rb_entry(n, struct pcpu_chunk, rb_node);
- }
-
- return chunk;
-}
-
-/**
- * pcpu_chunk_addr_insert - insert chunk into address rb tree
- * @new: chunk to insert
- *
- * Insert @new into address rb tree.
- *
- * CONTEXT:
- * pcpu_lock.
- */
-static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
-{
- struct rb_node **p, *parent;
-
- p = pcpu_chunk_rb_search(new->vm->addr, &parent);
- BUG_ON(*p);
- rb_link_node(&new->rb_node, parent, p);
- rb_insert_color(&new->rb_node, &pcpu_addr_root);
+ return pcpu_get_page_chunk(vmalloc_to_page(addr));
}
/**
@@ -755,6 +709,7 @@ static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
alloc_mask, 0);
if (!*pagep)
goto err;
+ pcpu_set_page_chunk(*pagep, chunk);
}
}
@@ -879,7 +834,6 @@ restart:
spin_lock_irq(&pcpu_lock);
pcpu_chunk_relocate(chunk, -1);
- pcpu_chunk_addr_insert(chunk);
goto restart;
area_found:
@@ -968,7 +922,6 @@ static void pcpu_reclaim(struct work_struct *work)
if (chunk == list_first_entry(head, struct pcpu_chunk, list))
continue;
- rb_erase(&chunk->rb_node, &pcpu_addr_root);
list_move(&chunk->list, &todo);
}
@@ -1147,7 +1100,8 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
if (reserved_size) {
schunk->free_size = reserved_size;
- pcpu_reserved_chunk = schunk; /* not for dynamic alloc */
+ pcpu_reserved_chunk = schunk;
+ pcpu_reserved_chunk_limit = static_size + reserved_size;
} else {
schunk->free_size = dyn_size;
dyn_size = 0; /* dynamic area covered */
@@ -1158,8 +1112,6 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
if (schunk->free_size)
schunk->map[schunk->map_used++] = schunk->free_size;
- pcpu_reserved_chunk_limit = static_size + schunk->free_size;
-
/* init dynamic chunk if necessary */
if (dyn_size) {
dchunk = alloc_bootmem(sizeof(struct pcpu_chunk));
@@ -1226,13 +1178,8 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
}
/* link the first chunk in */
- if (!dchunk) {
- pcpu_chunk_relocate(schunk, -1);
- pcpu_chunk_addr_insert(schunk);
- } else {
- pcpu_chunk_relocate(dchunk, -1);
- pcpu_chunk_addr_insert(dchunk);
- }
+ pcpu_first_chunk = dchunk ?: schunk;
+ pcpu_chunk_relocate(pcpu_first_chunk, -1);
/* we're done */
pcpu_base_addr = (void *)pcpu_chunk_addr(schunk, 0, 0);
--
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