Increase maximum Infiniband HCAs per-system

PATCH Superseded Alex Chiang 3 participants 12 messages Jan 29, 2010 – Feb 1, 2010 InfiniBand

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Alex Chiang

author

2010-01-29 21:44 UTC #0 lore raw

cover Increase maximum Infiniband HCAs per-system

Justin Chen discovered that Linux "only" supports 32 IB cards in a single system when testing a larger system with 40 cards and discovered that OFED only reported 32 HCAs.

This patchset doubles the number of HCAs allowed per system in a backwards-compatible manner.

Why only double? Well, it keeps the implementation very simple while also keeping the memory increase at a minimum. If the future requires even more HCAs per system, we can do a more complicated implementation then.

I tested this by inserting 4 IB cards into a system, and then changing IB_UVERBS_MAX_DEVICES = 2.

	dl585g2:~ # modprobe ib_uverbs
	dl585g2:~ # ls -l /dev/uverbs*
	crw-rw---- 1 root root 231, 192 Jan 28 06:59 /dev/uverbs0
	crw-rw---- 1 root root 231, 193 Jan 28 06:59 /dev/uverbs1
	crw-rw---- 1 root root 249,   0 Jan 28 06:59 /dev/uverbs2
	crw-rw---- 1 root root 249,   1 Jan 28 06:59 /dev/uverbs3

You can see that the uverbs devices are numbered in order, as one would expect, and that devices 2 and 3 have different major numbers while devices 0 and 1 retain the legacy, allocated major number.

I don't have access to a huge system to really test what happens at device 33, but it should just work, right? :)

I am also unaware of any OFED changes required (if that's even necessary), but then again, I'm just a simple kernel guy.

The final two patches are just something I discovered while using pahole to verify my changes in converting the *cdev pointer to an embedded struct. They don't save all that much, but they also don't change very much code either, so why not?

Thanks,
/ac

---

Alex Chiang (7):
IB/uverbs: convert *cdev to cdev in struct ib_uverbs_device IB/uverbs: remove dev_table
IB/uverbs: use stack variable 'devnum' in ib_uverbs_add_one IB/uverbs: use stack variable 'base' in ib_uverbs_add_one IB/uverbs: increase maximum devices supported IB/uverbs: pack struct ib_uverbs_event_file tighter IB/core: pack struct ib_device a little tighter

 drivers/infiniband/core/uverbs.h      |   11 ++-
 drivers/infiniband/core/uverbs_main.c |  106 +++++++++++++++++++++------------
 include/rdma/ib_verbs.h               |    4 +
 3 files changed, 76 insertions(+), 45 deletions(-)

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Alex Chiang

author

2010-01-29 21:45 UTC #1 lore raw

PATCH 1/7 IB/uverbs: convert *cdev to cdev in struct ib_uverbs_device

Instead of storing a pointer to a cdev, embed the entire struct cdev.

This change allows us to use the container_of() macro in ib_uverbs_open() in a future patch.

This change increases the size of struct ib_uverbs_device to 168 bytes across 3 cachelines from 80 bytes in 2 cachelines. However, we rearrange the members so that everything fits into the first cacheline except for the struct cdev. Finally, we don't touch the cdev in any fastpaths, so this change shouldn't negatively affect performance.

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs.h      |    7 ++++---
 drivers/infiniband/core/uverbs_main.c |   23 ++++++++++-------------
 2 files changed, 14 insertions(+), 16 deletions(-)

drivers/infiniband/core/uverbs.h +4 -3

index b3ea958..e695f65 100644
@@ -41,6 +41,7 @@
 #include <linux/idr.h>
 #include <linux/mutex.h>
 #include <linux/completion.h>
+#include <linux/cdev.h>
 
 #include <rdma/ib_verbs.h>
 #include <rdma/ib_umem.h>

@@ -69,12 +70,12 @@
 
 struct ib_uverbs_device {
 	struct kref				ref;
+	int					num_comp_vectors;
 	struct completion			comp;
-	int					devnum;
-	struct cdev			       *cdev;
 	struct device			       *dev;
 	struct ib_device		       *ib_dev;
-	int					num_comp_vectors;
+	int					devnum;
+	struct cdev			        cdev;
 };
 
 struct ib_uverbs_event_file {

drivers/infiniband/core/uverbs_main.c +10 ~~-13~~

index 5f284ff..5da9a73 100644
@@ -43,7 +43,6 @@
 #include <linux/sched.h>
 #include <linux/file.h>
 #include <linux/mount.h>
-#include <linux/cdev.h>
 
 #include <asm/uaccess.h>

@@ -761,17 +760,15 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	uverbs_dev->ib_dev           = device;
 	uverbs_dev->num_comp_vectors = device->num_comp_vectors;
 
-	uverbs_dev->cdev = cdev_alloc();
-	if (!uverbs_dev->cdev)
-		goto err;
-	uverbs_dev->cdev->owner = THIS_MODULE;
-	uverbs_dev->cdev->ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
-	kobject_set_name(&uverbs_dev->cdev->kobj, "uverbs%d", uverbs_dev->devnum);
-	if (cdev_add(uverbs_dev->cdev, IB_UVERBS_BASE_DEV + uverbs_dev->devnum, 1))
+	cdev_init(&uverbs_dev->cdev, NULL);
+	uverbs_dev->cdev.owner = THIS_MODULE;
+	uverbs_dev->cdev.ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
+	kobject_set_name(&uverbs_dev->cdev.kobj, "uverbs%d", uverbs_dev->devnum);
+	if (cdev_add(&uverbs_dev->cdev, IB_UVERBS_BASE_DEV + uverbs_dev->devnum, 1))
 		goto err_cdev;
 
 	uverbs_dev->dev = device_create(uverbs_class, device->dma_device,
-					uverbs_dev->cdev->dev, uverbs_dev,
+					uverbs_dev->cdev.dev, uverbs_dev,
 					"uverbs%d", uverbs_dev->devnum);
 	if (IS_ERR(uverbs_dev->dev))
 		goto err_cdev;

@@ -790,10 +787,10 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	return;
 
 err_class:
-	device_destroy(uverbs_class, uverbs_dev->cdev->dev);
+	device_destroy(uverbs_class, uverbs_dev->cdev.dev);
 
 err_cdev:
-	cdev_del(uverbs_dev->cdev);
+	cdev_del(&uverbs_dev->cdev);
 	clear_bit(uverbs_dev->devnum, dev_map);
 
 err:

@@ -811,8 +808,8 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 		return;
 
 	dev_set_drvdata(uverbs_dev->dev, NULL);
-	device_destroy(uverbs_class, uverbs_dev->cdev->dev);
-	cdev_del(uverbs_dev->cdev);
+	device_destroy(uverbs_class, uverbs_dev->cdev.dev);
+	cdev_del(&uverbs_dev->cdev);
 
 	spin_lock(&map_lock);
 	dev_table[uverbs_dev->devnum] = NULL;

Alex Chiang

author

2010-01-29 21:45 UTC #2 lore raw

PATCH 2/7 IB/uverbs: remove dev_table

In reply to Alex Chiang

dev_table's raison d'etre was to associate an inode back to a struct ib_uverbs_device.

However, now that we've converted ib_uverbs_device to contain an embedded cdev (instead of a *cdev), we can use the container_of() macro and cast back to the containing device.

There's no longer any need for dev_table, so get rid of it.

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs_main.c |   24 +++++-------------------
 1 files changed, 5 insertions(+), 19 deletions(-)

drivers/infiniband/core/uverbs_main.c +5 ~~-19~~

index 5da9a73..3f11292 100644
@@ -74,7 +74,6 @@ DEFINE_IDR(ib_uverbs_qp_idr);
 DEFINE_IDR(ib_uverbs_srq_idr);
 
 static DEFINE_SPINLOCK(map_lock);
-static struct ib_uverbs_device *dev_table[IB_UVERBS_MAX_DEVICES];
 static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,

@@ -616,14 +615,12 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
 /*
  * ib_uverbs_open() does not need the BKL:
  *
- *  - dev_table[] accesses are protected by map_lock, the
- *    ib_uverbs_device structures are properly reference counted, and
+ *  - the ib_uverbs_device structures are properly reference counted and
  *    everything else is purely local to the file being created, so
  *    races against other open calls are not a problem;
  *  - there is no ioctl method to race against;
- *  - the device is added to dev_table[] as the last part of module
- *    initialization, the open method will either immediately run
- *    -ENXIO, or all required initialization will be done.
+ *  - the open method will either immediately run -ENXIO, or all
+ *    required initialization will be done.
  */
 static int ib_uverbs_open(struct inode *inode, struct file *filp)
 {

@@ -631,13 +628,10 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 	struct ib_uverbs_file *file;
 	int ret;
 
-	spin_lock(&map_lock);
-	dev = dev_table[iminor(inode) - IB_UVERBS_BASE_MINOR];
+	dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev);
 	if (dev)
 		kref_get(&dev->ref);
-	spin_unlock(&map_lock);
-
-	if (!dev)
+	else
 		return -ENXIO;
 
 	if (!try_module_get(dev->ib_dev->owner)) {

@@ -778,10 +772,6 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	if (device_create_file(uverbs_dev->dev, &dev_attr_abi_version))
 		goto err_class;
 
-	spin_lock(&map_lock);
-	dev_table[uverbs_dev->devnum] = uverbs_dev;
-	spin_unlock(&map_lock);
-
 	ib_set_client_data(device, &uverbs_client, uverbs_dev);
 
 	return;

@@ -811,10 +801,6 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 	device_destroy(uverbs_class, uverbs_dev->cdev.dev);
 	cdev_del(&uverbs_dev->cdev);
 
-	spin_lock(&map_lock);
-	dev_table[uverbs_dev->devnum] = NULL;
-	spin_unlock(&map_lock);
-
 	clear_bit(uverbs_dev->devnum, dev_map);
 
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);

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Alex Chiang

author

2010-01-29 21:45 UTC #3 lore raw

PATCH 3/7 IB/uverbs: use stack variable 'devnum' in ib_uverbs_add_one

In reply to Alex Chiang

This change is not useful by itself, but it sets us up for a future change that allows us to dynamically allocate device numbers in case we have more than IB_UVERBS_MAX_DEVICES in the system.

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs_main.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

drivers/infiniband/core/uverbs_main.c +7 -5

index 3f11292..acae9ed 100644
@@ -730,6 +730,7 @@ static CLASS_ATTR(abi_version, S_IRUGO, show_abi_version, NULL);
 
 static void ib_uverbs_add_one(struct ib_device *device)
 {
+	int devnum;
 	struct ib_uverbs_device *uverbs_dev;
 
 	if (!device->alloc_ucontext)

@@ -743,12 +744,13 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	init_completion(&uverbs_dev->comp);
 
 	spin_lock(&map_lock);
-	uverbs_dev->devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
-	if (uverbs_dev->devnum >= IB_UVERBS_MAX_DEVICES) {
+	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
+	if (devnum >= IB_UVERBS_MAX_DEVICES) {
 		spin_unlock(&map_lock);
 		goto err;
 	}
-	set_bit(uverbs_dev->devnum, dev_map);
+	uverbs_dev->devnum = devnum;
+	set_bit(devnum, dev_map);
 	spin_unlock(&map_lock);
 
 	uverbs_dev->ib_dev           = device;

@@ -758,7 +760,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	uverbs_dev->cdev.owner = THIS_MODULE;
 	uverbs_dev->cdev.ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
 	kobject_set_name(&uverbs_dev->cdev.kobj, "uverbs%d", uverbs_dev->devnum);
-	if (cdev_add(&uverbs_dev->cdev, IB_UVERBS_BASE_DEV + uverbs_dev->devnum, 1))
+	if (cdev_add(&uverbs_dev->cdev, IB_UVERBS_BASE_DEV + devnum, 1))
 		goto err_cdev;
 
 	uverbs_dev->dev = device_create(uverbs_class, device->dma_device,

@@ -781,7 +783,7 @@ err_class:
 
 err_cdev:
 	cdev_del(&uverbs_dev->cdev);
-	clear_bit(uverbs_dev->devnum, dev_map);
+	clear_bit(devnum, dev_map);
 
 err:
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);

Alex Chiang

author

2010-01-29 21:45 UTC #4 lore raw

PATCH 4/7 IB/uverbs: use stack variable 'base' in ib_uverbs_add_one

In reply to Alex Chiang

This change is not useful by itself, but sets us up for a future change that allows us to support more than IB_UVERBS_MAX_DEVICES in a system.

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs_main.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

drivers/infiniband/core/uverbs_main.c +3 -2

index acae9ed..a5d441d 100644
@@ -730,7 +730,7 @@ static CLASS_ATTR(abi_version, S_IRUGO, show_abi_version, NULL);
 
 static void ib_uverbs_add_one(struct ib_device *device)
 {
-	int devnum;
+	int devnum, base;
 	struct ib_uverbs_device *uverbs_dev;
 
 	if (!device->alloc_ucontext)

@@ -750,6 +750,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 		goto err;
 	}
 	uverbs_dev->devnum = devnum;
+	base = devnum + IB_UVERBS_BASE_DEV;
 	set_bit(devnum, dev_map);
 	spin_unlock(&map_lock);

@@ -760,7 +761,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	uverbs_dev->cdev.owner = THIS_MODULE;
 	uverbs_dev->cdev.ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
 	kobject_set_name(&uverbs_dev->cdev.kobj, "uverbs%d", uverbs_dev->devnum);
-	if (cdev_add(&uverbs_dev->cdev, IB_UVERBS_BASE_DEV + devnum, 1))
+	if (cdev_add(&uverbs_dev->cdev, base, 1))
 		goto err_cdev;
 
 	uverbs_dev->dev = device_create(uverbs_class, device->dma_device,

Alex Chiang

author

2010-01-29 21:45 UTC #5 lore raw

PATCH 5/7 IB/uverbs: increase maximum devices supported

In reply to Alex Chiang

Some large systems may support more than IB_UVERBS_MAX_DEVICES (currently 32).

This change allows us to support more devices in a backwards-compatible manner. The first IB_UVERBS_MAX_DEVICES keep the same major/minor device numbers that they've always had.

If there are more than IB_UVERBS_MAX_DEVICES, we then dynamically request a new major device number (new minors start at 0).

This change increases the maximum number of HCAs to 64 (from 32).

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs_main.c |   56 +++++++++++++++++++++++++++++----
 1 files changed, 50 insertions(+), 6 deletions(-)

drivers/infiniband/core/uverbs_main.c +50 -6

index a5d441d..0555460 100644
@@ -728,6 +728,34 @@ static ssize_t show_abi_version(struct class *class, char *buf)
 }
 static CLASS_ATTR(abi_version, S_IRUGO, show_abi_version, NULL);
 
+static dev_t oflo_maj;
+static DECLARE_BITMAP(oflo_map, IB_UVERBS_MAX_DEVICES);
+
+/*
+ * If we have more than IB_UVERBS_MAX_DEVICES, dynamically overflow by
+ * requesting a new major number and doubling the number of max devices we
+ * support. It's stupid, but simple.
+ */
+static int find_oflo_devnum(void)
+{
+	int ret;
+
+	if (!oflo_maj) {
+		ret = alloc_chrdev_region(&oflo_maj, 0, IB_UVERBS_MAX_DEVICES,
+					  "infiniband_verbs");
+		if (ret) {
+			printk(KERN_ERR "user_verbs: couldn't register dynamic device number\n");
+			return ret;
+		}
+	}
+
+	ret = find_first_zero_bit(oflo_map, IB_UVERBS_MAX_DEVICES);
+	if (ret >= IB_UVERBS_MAX_DEVICES)
+		return -1;
+
+	return ret;
+}
+
 static void ib_uverbs_add_one(struct ib_device *device)
 {
 	int devnum, base;

@@ -747,11 +775,19 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
 	if (devnum >= IB_UVERBS_MAX_DEVICES) {
 		spin_unlock(&map_lock);
-		goto err;
+		devnum = find_oflo_devnum();
+		if (devnum < 0)
+			goto err;
+
+		spin_lock(&map_lock);
+		uverbs_dev->devnum = devnum + IB_UVERBS_MAX_DEVICES;
+		base = devnum + oflo_maj;
+		set_bit(devnum, oflo_map);
+	} else {
+		uverbs_dev->devnum = devnum;
+		base = devnum + IB_UVERBS_BASE_DEV;
+		set_bit(devnum, dev_map);
 	}
-	uverbs_dev->devnum = devnum;
-	base = devnum + IB_UVERBS_BASE_DEV;
-	set_bit(devnum, dev_map);
 	spin_unlock(&map_lock);
 
 	uverbs_dev->ib_dev           = device;

@@ -784,7 +820,10 @@ err_class:
 
 err_cdev:
 	cdev_del(&uverbs_dev->cdev);
-	clear_bit(devnum, dev_map);
+	if (oflo_maj)
+		clear_bit(devnum, oflo_map);
+	else
+		clear_bit(devnum, dev_map);
 
 err:
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);

@@ -804,7 +843,10 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 	device_destroy(uverbs_class, uverbs_dev->cdev.dev);
 	cdev_del(&uverbs_dev->cdev);
 
-	clear_bit(uverbs_dev->devnum, dev_map);
+	if (uverbs_dev->devnum < IB_UVERBS_MAX_DEVICES)
+		clear_bit(uverbs_dev->devnum, dev_map);
+	else
+		clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, oflo_map);
 
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
 	wait_for_completion(&uverbs_dev->comp);

@@ -894,6 +936,8 @@ static void __exit ib_uverbs_cleanup(void)
 	unregister_filesystem(&uverbs_event_fs);
 	class_destroy(uverbs_class);
 	unregister_chrdev_region(IB_UVERBS_BASE_DEV, IB_UVERBS_MAX_DEVICES);
+	if (oflo_maj)
+		unregister_chrdev_region(oflo_maj, IB_UVERBS_MAX_DEVICES);
 	idr_destroy(&ib_uverbs_pd_idr);
 	idr_destroy(&ib_uverbs_mr_idr);
 	idr_destroy(&ib_uverbs_mw_idr);

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Alex Chiang

author

2010-01-29 21:45 UTC #6 lore raw

PATCH 6/7 IB/uverbs: pack struct ib_uverbs_event_file tighter

In reply to Alex Chiang

Eliminate some padding in the structure by rearranging the members.

sizeof(struct ib_uverbs_event_file) is now 72 bytes (from 80) and more members now fit in the first cacheline.

Signed-off-by Alex Chiang <[email protected]>

---

 drivers/infiniband/core/uverbs.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

drivers/infiniband/core/uverbs.h +2 -2

index e695f65..e54d9ac 100644
@@ -80,13 +80,13 @@ struct ib_uverbs_device {
 
 struct ib_uverbs_event_file {
 	struct kref				ref;
+	int					is_async;
 	struct ib_uverbs_file		       *uverbs_file;
 	spinlock_t				lock;
+	int					is_closed;
 	wait_queue_head_t			poll_wait;
 	struct fasync_struct		       *async_queue;
 	struct list_head			event_list;
-	int					is_async;
-	int					is_closed;
 };
 
 struct ib_uverbs_file {

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Alex Chiang

author

2010-01-29 21:45 UTC #7 lore raw

PATCH 7/7 IB/core: pack struct ib_device a little tighter

In reply to Alex Chiang

A small change to reduce the size of ib_device to 1112 bytes (from 1128).

Signed-off-by Alex Chiang <[email protected]>

---

 include/rdma/ib_verbs.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

include/rdma/ib_verbs.h +2 -2

index 09509ed..a585e0f 100644
@@ -984,9 +984,9 @@ struct ib_device {
 	struct list_head              event_handler_list;
 	spinlock_t                    event_handler_lock;
 
+	spinlock_t                    client_data_lock;
 	struct list_head              core_list;
 	struct list_head              client_data_list;
-	spinlock_t                    client_data_lock;
 
 	struct ib_cache               cache;
 	int                          *pkey_tbl_len;

@@ -1144,8 +1144,8 @@ struct ib_device {
 		IB_DEV_UNREGISTERED
 	}                            reg_state;
 
-	u64			     uverbs_cmd_mask;
 	int			     uverbs_abi_ver;
+	u64			     uverbs_cmd_mask;
 
 	char			     node_desc[64];
 	__be64			     node_guid;

Roland Dreier

2010-01-29 22:54 UTC #8 lore raw

In reply to Alex Chiang

Quoted 6 lines

Justin Chen discovered that Linux "only" supports 32 IB cards in a single system when testing a larger system with 40 cards and discovered that OFED only reported 32 HCAs.
This patchset doubles the number of HCAs allowed per system in a backwards-compatible manner.

Looks like a really great start, some nice cleanups as well the added functionality. I've been meaning to use pahole for a while...

Have you considered drivers/infiniband/core/user_mad.c and ucm.c? I think user_mad.c is somewhat more important, as that is what allows an adapter to be used for running the SM. So I think we're still left with some potential issues around lots of adapters in one system. (I think use of ucm by real apps is minimal to nonexistent, but someday we should deal with that too)

- R.
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Alex Chiang

author

2010-01-29 23:41 UTC #9 lore raw

* Roland Dreier <[email protected]>:

Quoted 2 lines

Have you considered drivers/infiniband/core/user_mad.c and ucm.c?

Ah, darn. I had not considered those drivers. You're gonna make me learn a lot more about IB than I'd originally intended. ;)

Quoted 6 lines

I think user_mad.c is somewhat more important, as that is what allows an adapter to be used for running the SM. So I think we're still left with some potential issues around lots of adapters in one system. (I think use of ucm by real apps is minimal to nonexistent, but someday we should deal with that too)

Ok, a quick glance through those drivers shows:

	enum {
		IB_UMAD_MAX_PORTS  = 64,
		IB_UMAD_MAX_AGENTS = 32,

		IB_UMAD_MAJOR      = 231,
		IB_UMAD_MINOR_BASE = 0
	};

and

	enum {
		IB_UCM_MAJOR = 231,
		IB_UCM_BASE_MINOR = 224,
		IB_UCM_MAX_DEVICES = 32
	};

They're all sharing the same major number, so they'll all have to get the same treatment as the uverbs driver wrt overflow (to prevent minor number overlap).

What I'm a little unsure of is, does IB_UMAD_MAX_AGENTS need to double too? We don't export the agent id in the filesystem anywhere, but we do give it to the user via an ioctl. That's just used for book keeping purposes but...

Currently, there are 2x as many ports as there are agents. Do we want to keep that ratio, or would it be ok to have 4x as many ports as there are agents?

Thanks (and sorry for the n00b questions).

/ac
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Roland Dreier

2010-01-30 07:13 UTC #10 lore raw

Quoted 4 lines

What I'm a little unsure of is, does IB_UMAD_MAX_AGENTS need to double too? We don't export the agent id in the filesystem anywhere, but we do give it to the user via an ioctl. That's just used for book keeping purposes but...

I don't think so. That is a limit on "agents" registered per open file, so it is orthogonal to the number of devices.

- R.
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Hal Rosenstock

2010-02-01 12:55 UTC #11 lore raw

In reply to Alex Chiang

Quoted 36 lines · Alex Chiang

* Roland Dreier <[email protected]>:
Quoted 2 lines
Have you considered drivers/infiniband/core/user_mad.c and ucm.c?
Ah, darn. I had not considered those drivers. You're gonna make me learn a lot more about IB than I'd originally intended. ;)
Quoted 6 lines
I think user_mad.c is somewhat more important, as that is what allows an adapter to be used for running the SM. So I think we're still left with some potential issues around lots of adapters in one system. (I think use of ucm by real apps is minimal to nonexistent, but someday we should deal with that too)
Ok, a quick glance through those drivers shows:
enum {
IB_UMAD_MAX_PORTS = 64,
IB_UMAD_MAX_AGENTS = 32,
IB_UMAD_MAJOR = 231,
IB_UMAD_MINOR_BASE = 0
};
and
enum {
IB_UCM_MAJOR = 231,
IB_UCM_BASE_MINOR = 224,
IB_UCM_MAX_DEVICES = 32
};
They're all sharing the same major number, so they'll all have to get the same treatment as the uverbs driver wrt overflow (to prevent minor number overlap).

Quoted 8 lines

What I'm a little unsure of is, does IB_UMAD_MAX_AGENTS need to double too? We don't export the agent id in the filesystem anywhere, but we do give it to the user via an ioctl. That's just used for book keeping purposes but...
Currently, there are 2x as many ports as there are agents. Do we want to keep that ratio, or would it be ok to have 4x as many ports as there are agents?

I think it's 2x as many ports as devices (based on the common HCAs being 2 ports max). This should be maintained as that is still the case.

-- Hal

Quoted 9 lines

Thanks (and sorry for the n00b questions).
/ac
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