[PATCH V4 1/2] IB/core: Add support for enhanced atomic operations

[PATCH V4 1/2] IB/core: Add support for enhanced atomic operations

[Vladimir Sokolovsky]

- Add a new IB_WR_MASKED_ATOMIC_CMP_AND_SWP and IB_WR_MASKED_ATOMIC_FETCH_AND_ADD send
  opcodes that can be used to mark a "masked atomic compare and swap" and
  "masked atomic fetch and add" work request correspondingly.
- Add masked_atomic_cap capability.
- Add mask fields to atomic struct of ib_send_wr
- Add new opcodes to ib_wc_opcode

Masked Compare and Swap (MskCmpSwap)
The MskCmpSwap atomic operation is an extension to the CmpSwap operation
defined in the IB spec. MskCmpSwap allows the user to select a portion of the
64 bit target data for the “compare” check as well as to restrict the swap to a
(possibly different) portion. The pseudo code below describes the operation:

| atomic_response = *va
| if (!((compare_add ^ *va) & compare_add_mask)) then
|     *va = (*va & ~(swap_mask)) | (swap & swap_mask)
|
| return atomic_response

The additional operands are carried in the Extended Transport Header. Atomic
response generation and packet format for MskCmpSwap is as for standard IB
Atomic operations.

Masked Fetch and Add (MFetchAdd)
The MFetchAdd Atomic operation extends the functionality of the standard IB
FetchAdd by allowing the user to split the target into multiple fields of
selectable length. The atomic add is done independently on each one of this
fields. A bit set in the field_boundary parameter specifies the field
boundaries. The pseudo code below describes the operation:

| bit_adder(ci, b1, b2, *co)
| {
|	value = ci + b1 + b2
|	*co = !!(value & 2)
|
|	return value & 1
| }
|
| #define MASK_IS_SET(mask, attr)      (!!((mask)&(attr)))
| bit_position = 1
| carry = 0
| atomic_response = 0
|
| for i = 0 to 63
| {
|         if ( i != 0 )
|                 bit_position =  bit_position << 1
|
|         bit_add_res = bit_adder(carry, MASK_IS_SET(*va, bit_position), MASK_IS_SET(compare_add, bit_position), &new_carry)
|         if (bit_add_res)
|                 atomic_response |= bit_position
|
|         carry = ((new_carry) && (!MASK_IS_SET(compare_add_mask, bit_position)))
| }
|
| return atomic_response

Signed-off-by: Vladimir Sokolovsky <vlad-VPRAkNaXOzVS1MOuV/RT9w@public.gmane.org>
---
 include/rdma/ib_verbs.h |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 09509ed..8ef6858 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -136,6 +136,7 @@ struct ib_device_attr {
 	int			max_qp_init_rd_atom;
 	int			max_ee_init_rd_atom;
 	enum ib_atomic_cap	atomic_cap;
+	enum ib_atomic_cap	masked_atomic_cap;
 	int			max_ee;
 	int			max_rdd;
 	int			max_mw;
@@ -467,6 +468,8 @@ enum ib_wc_opcode {
 	IB_WC_LSO,
 	IB_WC_LOCAL_INV,
 	IB_WC_FAST_REG_MR,
+	IB_WC_MASKED_COMP_SWAP,
+	IB_WC_MASKED_FETCH_ADD,
 /*
  * Set value of IB_WC_RECV so consumers can test if a completion is a
  * receive by testing (opcode & IB_WC_RECV).
@@ -689,6 +692,8 @@ enum ib_wr_opcode {
 	IB_WR_RDMA_READ_WITH_INV,
 	IB_WR_LOCAL_INV,
 	IB_WR_FAST_REG_MR,
+	IB_WR_MASKED_ATOMIC_CMP_AND_SWP,
+	IB_WR_MASKED_ATOMIC_FETCH_AND_ADD,
 };
 
 enum ib_send_flags {
@@ -731,6 +736,8 @@ struct ib_send_wr {
 			u64	remote_addr;
 			u64	compare_add;
 			u64	swap;
+			u64	compare_add_mask;
+			u64	swap_mask;
 			u32	rkey;
 		} atomic;
 		struct {
-- 
1.7.0.3

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Re: [PATCH V4 1/2] IB/core: Add support for enhanced atomic operations

[Håkon Bugge]

On Apr 14, 2010, at 16:23 , Vladimir Sokolovsky wrote:

> The additional operands are carried in the Extended Transport Header

Is this a newly defined ETH which follows the AETH on the wire?



Thanks, Håkon
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Re: [PATCH V4 1/2] IB/core: Add support for enhanced atomic operations

[Vladimir Sokolovsky]

Håkon Bugge wrote:
> On Apr 14, 2010, at 16:23 , Vladimir Sokolovsky wrote:
> 
>> The additional operands are carried in the Extended Transport Header
> 
> Is this a newly defined ETH which follows the AETH on the wire?
> 
> 
> 
> Thanks, Håkon
> 

Yes,
Atomic masked Fetch and Add uses first 64 bits to provide the date to add,
and the second 64 bits provide the field boundary:

Swap (or Add) data high [63:32]
Swap (or Add) data low  [31:0]
Compare data (or Field boundary) high [63:32]
Compare data (or Field boundary) high [31:0]

Atomic masked Compare and Swap uses:

Swap (or Add) data high [63:32]
Swap (or Add) data low  [31:0]
Compare data high [63:32]
Compare data high [31:0]
Swap mask high [63:32]
Swap mask low  [31:0]
Compare mask high [63:32]
Compare mask low  [31:0]


Regards,
Vladimir
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