core: allocate control structures using an own kmem_cache

Testing /dev/urandom versus zzero-0-1-data (the random device) shows this increases performance by 0.1 usecs per block. We are now just over 0.7 usecs per block on my development PC. This also introduces zio-core.c with generic stuff. We agree that zio-sys will become zio-sysfs over time. Signed-off-by: Alessandro Rubini <rubini@gnudd.com> Acked-by: Federico Vaga <federico.vaga@gmail.com> Conflicts: Makefile

core: allocate control structures using an own kmem_cache
Testing /dev/urandom versus zzero-0-1-data (the random device) shows this increases performance by 0.1 usecs per block. We are now just over 0.7 usecs per block on my development PC. This also introduces zio-core.c with generic stuff. We agree that zio-sys will become zio-sysfs over time. Signed-off-by: Alessandro Rubini <rubini@gnudd.com> Acked-by: Federico Vaga <federico.vaga@gmail.com> Conflicts: Makefile
cd0373b9 · Alessandro Rubini · ae24b85a · cd0373b9 · cd0373b9 · cd0373b9
Commit cd0373b9 authored Jan 31, 2012 by Alessandro Rubini
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Makefile Makefile +1 -1

zio-buffer.h include/linux/zio-buffer.h +7 -21

zio-core.c zio-core.c +52 -0

zio-sys.c zio-sys.c +5 -0

No files found.
--- a/Makefile
+++ b/Makefile
 LINUX ?= /lib/modules/$(shell uname -r)/build

-zio-objs := zio-cdev.o zio-sys.o
+zio-objs := zio-core.o zio-cdev.o zio-sys.o
 zio-objs += buffers/zio-buf-kmalloc.o triggers/zio-trig-user.o

 obj-m = zio.o

--- a/include/linux/zio-buffer.h
+++ b/include/linux/zio-buffer.h
@@ -16,27 +16,6 @@

 #define ZIO_DEFAULT_BUFFER "kmalloc" /* For devices with no own buffer type */

-/* FIXME: use a kmem_cache and real functions for control alloc/free */
-static inline struct zio_control *zio_alloc_control(gfp_t gfp)
-{
-	struct zio_control *ctrl;
-
-	ctrl = kzalloc(sizeof(*ctrl), gfp);
-	if (!ctrl)
-		return NULL;
-	ctrl->major_version = ZIO_MAJOR_VERSION;
-	ctrl->minor_version = ZIO_MINOR_VERSION;
-	if (ntohl(1) == 1)
-		ctrl->flags |= ZIO_CONTROL_BIG_ENDIAN;
-	else
-		ctrl->flags |= ZIO_CONTROL_LITTLE_ENDIAN;
-	return ctrl;
-}
-static inline void zio_free_control(struct zio_control *ctrl)
-{
-	kfree(ctrl);
-}
-
 /*
 * The following structure defines a buffer type, with methods.
 * An instance is created for each channel using it
@@ -75,6 +54,13 @@ int __must_check zio_register_buf(struct zio_buffer_type *zbuf,
 				  const char *name);
 void zio_unregister_buf(struct zio_buffer_type *zbuf);

+/* We have our own kmem_cache (a.k.a. slab) for control structures */
+int zio_slab_init(void);
+void zio_slab_exit(void);
+struct zio_control *zio_alloc_control(gfp_t gfp);
+void zio_free_control(struct zio_control *ctrl);
+
+
 struct zio_bi {
 	struct zio_obj_head	head;
 	struct list_head	list;		/* instance list */

--- a/zio-core.c
+++ b/zio-core.c
+/* Alessandro Rubini, Federico Vaga for CERN, 2011, GNU GPLv2 or later */
+
+/*
+ * This file includes functions that build up the zio core, but are not
+ * strictly related to sysfs and configuration. Those are in zio-sysfs.c
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/zio.h>
+#include <linux/zio-buffer.h>
+
+/*
+ * We use a local slab for control structures.
+ */
+static struct kmem_cache *zio_ctrl_slab;
+
+struct zio_control *zio_alloc_control(gfp_t gfp)
+{
+	struct zio_control *ctrl;
+
+	ctrl = kmem_cache_alloc(zio_ctrl_slab, gfp);
+	if (!ctrl)
+		return NULL;
+	ctrl->major_version = ZIO_MAJOR_VERSION;
+	ctrl->minor_version = ZIO_MINOR_VERSION;
+	if (ntohl(1) == 1)
+		ctrl->flags |= ZIO_CONTROL_BIG_ENDIAN;
+	else
+		ctrl->flags |= ZIO_CONTROL_LITTLE_ENDIAN;
+	return ctrl;
+}
+
+void zio_free_control(struct zio_control *ctrl)
+{
+	kmem_cache_free(zio_ctrl_slab, ctrl);
+}
+
+int __init zio_slab_init(void)
+{
+	zio_ctrl_slab = KMEM_CACHE(zio_control, 0);
+	if (!zio_ctrl_slab)
+		return -ENOMEM;
+	return 0;
+}
+
+void zio_slab_exit(void) /* not __exit: called from zio_init on failures */
+{
+	if (zio_ctrl_slab)
+		kmem_cache_destroy(zio_ctrl_slab);
+	return;
+}
--- a/zio-sys.c
+++ b/zio-sys.c
@@ -1745,6 +1745,9 @@ static int __init zio_init(void)
 	BUILD_BUG_ON(ZATTR_STD_NUM_ZBUF != ARRAY_SIZE(zio_zbuf_attr_names));
 	BUILD_BUG_ON(ZATTR_STD_NUM_TRIG != ARRAY_SIZE(zio_trig_attr_names));

+	err = zio_slab_init();
+	if (err)
+		return err;
 	/* Initialize char device */
 	err = __zio_register_cdev();
 	if (err)
@@ -1774,6 +1777,7 @@ static int __init zio_init(void)
 out_kobj:
 	__zio_unregister_cdev();
 out_cdev:
+	zio_slab_exit();
 	return err;
 }

@@ -1792,6 +1796,7 @@ static void __exit zio_exit(void)

 	/* Remove char device */
 	__zio_unregister_cdev();
+	zio_slab_exit();

 	pr_info("zio-core had been unloaded\n");
 	return;