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ib_srpt: Use a spinlock to protect ch->req_lim and ch->req_lim_delta changes instead of using atomics. Reduces the time spent in the ib_srpt_compl thread with a little bit more than 10%.

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@3558 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2011-06-08 18:13:30 +00:00
parent aa78149881
commit 7943d6466e
2 changed files with 77 additions and 23 deletions
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86
srpt/src/ib_srpt.c
View File

@@ -228,6 +228,53 @@ static bool srpt_test_and_set_ch_state(struct srpt_rdma_ch *ch,
return prev == old;
}
/**
* srpt_adjust_req_lim() - Adjust ch->req_lim and ch->req_lim_delta atomically.
*
* Returns the new value of ch->req_lim.
*/
static int srpt_adjust_req_lim(struct srpt_rdma_ch *ch, int req_lim_change,
int req_lim_delta_change)
{
int req_lim;
unsigned long flags;
spin_lock_irqsave(&ch->spinlock, flags);
ch->req_lim += req_lim_change;
req_lim = ch->req_lim;
ch->req_lim_delta += req_lim_delta_change;
spin_unlock_irqrestore(&ch->spinlock, flags);
return req_lim;
}
/**
* srpt_inc_req_lim() - Increase ch->req_lim and decrease ch->req_lim_delta.
*
* Returns the previous value of ch->req_lim_delta.
*/
static int srpt_inc_req_lim(struct srpt_rdma_ch *ch)
{
int req_lim_delta;
unsigned long flags;
spin_lock_irqsave(&ch->spinlock, flags);
req_lim_delta = ch->req_lim_delta;
ch->req_lim += 1 + req_lim_delta;
ch->req_lim_delta = 0;
spin_unlock_irqrestore(&ch->spinlock, flags);
return req_lim_delta;
}
/**
* srpt_undo_inc_req_lim() - Undo the effect of srpt_inc_req_lim.
*/
static int srpt_undo_inc_req_lim(struct srpt_rdma_ch *ch, int req_lim_delta)
{
return srpt_adjust_req_lim(ch, -(1 + req_lim_delta), req_lim_delta);
}
/**
* srpt_event_handler() - Asynchronous IB event callback function.
*
@@ -1295,10 +1342,13 @@ static void srpt_handle_send_err_comp(struct srpt_rdma_ch *ch, u64 wr_id,
&& state != SRPT_STATE_NEED_DATA
&& state != SRPT_STATE_DONE);
/* If SRP_RSP sending failed, undo the ch->req_lim change. */
/*
* If SRP_RSP sending failed, undo the ch->req_lim and ch->req_lim_delta
* changes.
*/
if (state == SRPT_STATE_CMD_RSP_SENT
|| state == SRPT_STATE_MGMT_RSP_SENT)
atomic_dec(&ch->req_lim);
srpt_undo_inc_req_lim(ch, ioctx->req_lim_delta);
if (state != SRPT_STATE_DONE) {
if (scmnd)
srpt_abort_cmd(ioctx, context);
@@ -1447,8 +1497,8 @@ static int srpt_build_cmd_rsp(struct srpt_rdma_ch *ch,
memset(srp_rsp, 0, sizeof *srp_rsp);
srp_rsp->opcode = SRP_RSP;
srp_rsp->req_lim_delta = __constant_cpu_to_be32(1
+ atomic_xchg(&ch->req_lim_delta, 0));
srp_rsp->req_lim_delta =
__constant_cpu_to_be32(ioctx->req_lim_delta + 1);
srp_rsp->tag = tag;
srp_rsp->status = status;
@@ -1500,8 +1550,8 @@ static int srpt_build_tskmgmt_rsp(struct srpt_rdma_ch *ch,
memset(srp_rsp, 0, sizeof *srp_rsp);
srp_rsp->opcode = SRP_RSP;
srp_rsp->req_lim_delta = __constant_cpu_to_be32(1
+ atomic_xchg(&ch->req_lim_delta, 0));
srp_rsp->req_lim_delta
= __constant_cpu_to_be32(ioctx->req_lim_delta + 1);
srp_rsp->tag = tag;
if (rsp_code != SRP_TSK_MGMT_SUCCESS) {
@@ -1770,7 +1820,7 @@ static void srpt_process_rcv_completion(struct ib_cq *cq,
if (wc->status == IB_WC_SUCCESS) {
int req_lim;
req_lim = atomic_dec_return(&ch->req_lim);
req_lim = srpt_adjust_req_lim(ch, -1, 0);
if (unlikely(req_lim < 0))
PRINT_ERROR("req_lim = %d < 0", req_lim);
ioctx = sdev->ioctx_ring[index];
@@ -2392,8 +2442,8 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
rsp->buf_fmt = __constant_cpu_to_be16(SRP_BUF_FORMAT_DIRECT
| SRP_BUF_FORMAT_INDIRECT);
rsp->req_lim_delta = cpu_to_be32(ch->rq_size);
atomic_set(&ch->req_lim, ch->rq_size);
atomic_set(&ch->req_lim_delta, 0);
ch->req_lim = ch->rq_size;
ch->req_lim_delta = 0;
/* create cm reply */
rep_param->qp_num = ch->qp->qp_num;
@@ -2463,7 +2513,7 @@ static void srpt_cm_rej_recv(struct ib_cm_id *cm_id)
}
/**
* srpt_cm_rtu_recv() - Process an IB_CM_RTU_RECEIVED or IB_CM_USER_ESTABLISHED event.
* srpt_cm_rtu_recv() - Process IB CM RTU_RECEIVED and USER_ESTABLISHED events.
*
* An IB_CM_RTU_RECEIVED message indicates that the connection is established
* and that the recipient may begin transmitting (RTU = ready to use).
@@ -2993,7 +3043,7 @@ static int srpt_xmit_response(struct scst_cmd *scmnd)
spin_unlock(&ioctx->spinlock);
if (unlikely(scst_cmd_aborted(scmnd))) {
atomic_inc(&ch->req_lim_delta);
srpt_adjust_req_lim(ch, 0, 1);
srpt_abort_cmd(ioctx, SCST_CONTEXT_SAME);
goto out;
}
@@ -3016,8 +3066,7 @@ static int srpt_xmit_response(struct scst_cmd *scmnd)
}
}
atomic_inc(&ch->req_lim);
ioctx->req_lim_delta = srpt_inc_req_lim(ch);
resp_len = srpt_build_cmd_rsp(ch, ioctx,
scst_cmd_get_tag(scmnd),
scst_cmd_get_status(scmnd),
@@ -3027,7 +3076,7 @@ static int srpt_xmit_response(struct scst_cmd *scmnd)
if (srpt_post_send(ch, ioctx, resp_len)) {
srpt_unmap_sg_to_ib_sge(ch, ioctx);
srpt_set_cmd_state(ioctx, state);
atomic_dec(&ch->req_lim);
srpt_undo_inc_req_lim(ch, ioctx->req_lim_delta);
PRINT_WARNING("sending response failed for tag %llu - retrying",
scst_cmd_get_tag(scmnd));
ret = SCST_TGT_RES_QUEUE_FULL;
@@ -3064,8 +3113,7 @@ static void srpt_tsk_mgmt_done(struct scst_mgmt_cmd *mcmnd)
srpt_set_cmd_state(ioctx, SRPT_STATE_MGMT_RSP_SENT);
WARN_ON(ioctx->state == SRPT_STATE_DONE);
atomic_inc(&ch->req_lim);
ioctx->req_lim_delta = srpt_inc_req_lim(ch);
rsp_len = srpt_build_tskmgmt_rsp(ch, ioctx,
scst_to_srp_tsk_mgmt_status(
scst_mgmt_cmd_get_status(mcmnd)),
@@ -3079,7 +3127,7 @@ static void srpt_tsk_mgmt_done(struct scst_mgmt_cmd *mcmnd)
if (srpt_post_send(ch, ioctx, rsp_len)) {
PRINT_ERROR("%s", "Sending SRP_RSP response failed.");
srpt_put_send_ioctx(ioctx);
atomic_dec(&ch->req_lim);
srpt_undo_inc_req_lim(ch, ioctx->req_lim_delta);
}
}
@@ -3322,7 +3370,7 @@ static ssize_t show_req_lim(struct kobject *kobj,
ch = scst_sess_get_tgt_priv(scst_sess);
if (!ch)
return -ENOENT;
return sprintf(buf, "%d\n", atomic_read(&ch->req_lim));
return sprintf(buf, "%d\n", ch->req_lim);
}
static ssize_t show_req_lim_delta(struct kobject *kobj,
@@ -3335,7 +3383,7 @@ static ssize_t show_req_lim_delta(struct kobject *kobj,
ch = scst_sess_get_tgt_priv(scst_sess);
if (!ch)
return -ENOENT;
return sprintf(buf, "%d\n", atomic_read(&ch->req_lim_delta));
return sprintf(buf, "%d\n", ch->req_lim_delta);
}
static const struct kobj_attribute srpt_req_lim_attr =

14
srpt/src/ib_srpt.h
View File

@@ -216,7 +216,7 @@ struct srpt_tsk_mgmt {
* @sg: Pointer to sg-list associated with this I/O context.
* @spinlock: Protects 'state'.
* @state: I/O context state.
* @scmd: SCST command data structure.
* @scmnd: SCST command data structure.
* @dir:
* @free_list: Node in srpt_rdma_ch.free_list.
* @sg_cnt: SG-list size.
@@ -224,6 +224,9 @@ struct srpt_tsk_mgmt {
* @n_rdma_ius: Number of elements in the rdma_ius array.
* @n_rdma:
* @n_rbuf: Number of data buffers in the received SRP command.
* @req_lim_delta: one less than the req_lim_delta value field in the latest
* SRP response sent.
* @tsk_mgmt:
*/
struct srpt_send_ioctx {
struct srpt_ioctx ioctx;
@@ -242,6 +245,7 @@ struct srpt_send_ioctx {
u16 n_rdma_ius;
u8 n_rdma;
u8 n_rbuf;
int req_lim_delta;
struct srpt_tsk_mgmt tsk_mgmt;
};
@@ -279,7 +283,9 @@ enum rdma_ch_state {
* @max_ti_iu_len: maximum target-to-initiator information unit length.
* @req_lim: request limit: maximum number of requests that may be sent
* by the initiator without having received a response.
* @req_lim_delta:
* @req_lim_delta: one less than the req_lim_delta value that will be included
* in the next reply sent to the initiator. See also the SRP
* credit algorithm in the SRP spec.
* @spinlock: Protects free_list.
* @free_list: Head of list with free send I/O contexts.
* @ioctx_ring:
@@ -303,8 +309,8 @@ struct srpt_rdma_ch {
u8 i_port_id[16];
u8 t_port_id[16];
int max_ti_iu_len;
atomic_t req_lim;
atomic_t req_lim_delta;
int req_lim;
int req_lim_delta;
spinlock_t spinlock;
struct list_head free_list;
struct srpt_send_ioctx **ioctx_ring;