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Date: Thu, 3 Dec 2009 18:45:31 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH -v2] ext4: Use slab allocator for sub-page sized allocations
Now that the SLUB seems to be fixed so that it respects the requested
alignment, use kmem_cache_alloc() to allocator if the block size of
the buffer heads to be allocated is less than the page size.
Previously, we were using 16k page on a Power system for each buffer,
even when the file system was using 1k or 4k block size.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
Address the concerns found in https://bugzilla.lustre.org/show_bug.cgi?id=19184
fs/jbd2/journal.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/jbd2.h | 11 +---
2 files changed, 134 insertions(+), 9 deletions(-)
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 3f473fa..5824353 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -39,6 +39,8 @@
#include <linux/seq_file.h>
#include <linux/math64.h>
#include <linux/hash.h>
+#include <linux/log2.h>
+#include <linux/vmalloc.h>
#define CREATE_TRACE_POINTS
#include <trace/events/jbd2.h>
@@ -92,6 +94,7 @@ EXPORT_SYMBOL(jbd2_journal_begin_ordered_truncate);
static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
static void __journal_abort_soft (journal_t *journal, int errno);
+static int jbd2_journal_create_slab(size_t slab_size);
/*
* Helper function used to manage commit timeouts
@@ -1247,6 +1250,13 @@ int jbd2_journal_load(journal_t *journal)
}
}
+ /*
+ * Create a slab for this blocksize
+ */
+ err = jbd2_journal_create_slab(be32_to_cpu(sb->s_blocksize));
+ if (err)
+ return err;
+
/* Let the recovery code check whether it needs to recover any
* data from the journal. */
if (jbd2_journal_recover(journal))
@@ -1806,6 +1816,127 @@ size_t journal_tag_bytes(journal_t *journal)
}
/*
+ * JBD memory management
+ *
+ * These functions are used to allocate block-sized chunks of memory
+ * used for making copies of buffer_head data. Very often it will be
+ * page-sized chunks of data, but sometimes it will be in
+ * sub-page-size chunks. (For example, 16k pages on Power systems
+ * with a 4k block file system.) For blocks smaller than a page, we
+ * use a SLAB allocator. There are slab caches for each block size,
+ * which are allocated at mount time, if necessary, and we only free
+ * (all of) the slab caches when/if the jbd2 module is unloaded. For
+ * this reason we don't need to a mutex to protect access to
+ * jbd2_slab[] allocating or releasing memory; only in
+ * jbd2_journal_create_slab().
+ */
+#define JBD2_MAX_SLABS 8
+static struct kmem_cache *jbd2_slab[JBD2_MAX_SLABS];
+static DECLARE_MUTEX(jbd2_slab_create_sem);
+
+static const char *jbd2_slab_names[JBD2_MAX_SLABS] = {
+ "jbd2_1k", "jbd2_2k", "jbd2_4k", "jbd2_8k",
+ "jbd2_16k", "jbd2_32k", "jbd2_64k", "jbd2_128k"
+};
+
+
+static void jbd2_journal_destroy_slabs(void)
+{
+ int i;
+
+ for (i = 0; i < JBD2_MAX_SLABS; i++) {
+ if (jbd2_slab[i])
+ kmem_cache_destroy(jbd2_slab[i]);
+ jbd2_slab[i] = NULL;
+ }
+}
+
+static int jbd2_journal_create_slab(size_t size)
+{
+ int i = order_base_2(size) - 10;
+ size_t slab_size;
+
+ if (size == PAGE_SIZE)
+ return 0;
+
+ if (i >= JBD2_MAX_SLABS)
+ return -EINVAL;
+
+ if (unlikely(i < 0))
+ i = 0;
+ down(&jbd2_slab_create_sem);
+ if (jbd2_slab[i]) {
+ up(&jbd2_slab_create_sem);
+ return 0; /* Already created */
+ }
+
+ slab_size = 1 << (i+10);
+ jbd2_slab[i] = kmem_cache_create(jbd2_slab_names[i], slab_size,
+ slab_size, 0, NULL);
+ up(&jbd2_slab_create_sem);
+ if (!jbd2_slab[i]) {
+ printk(KERN_EMERG "JBD2: no memory for jbd2_slab cache\n");
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+static struct kmem_cache *get_slab(size_t size)
+{
+ int i = order_base_2(size) - 10;
+
+ BUG_ON(i >= JBD2_MAX_SLABS);
+ if (unlikely(i < 0))
+ i = 0;
+ BUG_ON(jbd2_slab[i] == 0);
+ return jbd2_slab[i];
+}
+
+void *jbd2_alloc(size_t size, gfp_t flags)
+{
+ void *ptr;
+
+ BUG_ON(size & (size-1)); /* Must be a power of 2 */
+
+ flags |= __GFP_REPEAT;
+ if (size == PAGE_SIZE)
+ ptr = (void *)__get_free_pages(flags, 0);
+ else if (size > PAGE_SIZE) {
+ int order = get_order(size);
+
+ if (order < 3)
+ ptr = (void *)__get_free_pages(flags, order);
+ else
+ ptr = vmalloc(size);
+ } else
+ ptr = kmem_cache_alloc(get_slab(size), flags);
+
+ /* Check alignment; SLUB has gotten this wrong in the past,
+ * and this can lead to user data corruption! */
+ BUG_ON(((unsigned long) ptr) & (size-1));
+
+ return ptr;
+}
+
+void jbd2_free(void *ptr, size_t size)
+{
+ if (size == PAGE_SIZE) {
+ free_pages((unsigned long)ptr, 0);
+ return;
+ }
+ if (size > PAGE_SIZE) {
+ int order = get_order(size);
+
+ if (order < 3)
+ free_pages((unsigned long)ptr, order);
+ else
+ vfree(ptr);
+ return;
+ }
+ kmem_cache_free(get_slab(size), ptr);
+};
+
+/*
* Journal_head storage management
*/
static struct kmem_cache *jbd2_journal_head_cache;
@@ -2202,6 +2333,7 @@ static void jbd2_journal_destroy_caches(void)
jbd2_journal_destroy_revoke_caches();
jbd2_journal_destroy_jbd2_journal_head_cache();
jbd2_journal_destroy_handle_cache();
+ jbd2_journal_destroy_slabs();
}
static int __init journal_init(void)
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index f1011f7..a7a8c7a 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -69,15 +69,8 @@ extern u8 jbd2_journal_enable_debug;
#define jbd_debug(f, a...) /**/
#endif
-static inline void *jbd2_alloc(size_t size, gfp_t flags)
-{
- return (void *)__get_free_pages(flags, get_order(size));
-}
-
-static inline void jbd2_free(void *ptr, size_t size)
-{
- free_pages((unsigned long)ptr, get_order(size));
-};
+extern void *jbd2_alloc(size_t size, gfp_t flags);
+extern void jbd2_free(void *ptr, size_t size);
#define JBD2_MIN_JOURNAL_BLOCKS 1024
--
1.6.5.216.g5288a.dirty
--
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