Give block I/O interface multiple (8) execution threads.
On parallel random I/O this allows better utilize wide storage pools. To not confuse prefetcher on linear I/O, consecutive requests are executed sequentially, following the same logic as was earlier implemented in CTL. Benchmarks of virtual AHCI disk, backed by ZVOL on RAID10 pool of 4 HDDs, show ~3.5 times random read performance improvements, while no degradation on linear I/O. MFC after: 2 weeks
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mav
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@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
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#define BLOCKIF_SIG 0xb109b109
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#define BLOCKIF_MAXREQ 33
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#define BLOCKIF_NUMTHR 8
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enum blockop {
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BOP_READ,
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@ -65,6 +66,7 @@ enum blockop {
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enum blockstat {
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BST_FREE,
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BST_BLOCK,
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BST_PEND,
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BST_BUSY,
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BST_DONE
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@ -76,6 +78,7 @@ struct blockif_elem {
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enum blockop be_op;
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enum blockstat be_status;
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pthread_t be_tid;
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off_t be_block;
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};
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struct blockif_ctxt {
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@ -88,16 +91,15 @@ struct blockif_ctxt {
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int bc_sectsz;
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int bc_psectsz;
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int bc_psectoff;
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pthread_t bc_btid;
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int bc_closing;
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pthread_t bc_btid[BLOCKIF_NUMTHR];
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pthread_mutex_t bc_mtx;
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pthread_cond_t bc_cond;
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int bc_closing;
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/* Request elements and free/pending/busy queues */
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TAILQ_HEAD(, blockif_elem) bc_freeq;
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TAILQ_HEAD(, blockif_elem) bc_pendq;
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TAILQ_HEAD(, blockif_elem) bc_busyq;
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u_int bc_req_count;
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struct blockif_elem bc_reqs[BLOCKIF_MAXREQ];
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};
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@ -116,58 +118,83 @@ static int
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blockif_enqueue(struct blockif_ctxt *bc, struct blockif_req *breq,
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enum blockop op)
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{
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struct blockif_elem *be;
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assert(bc->bc_req_count < BLOCKIF_MAXREQ);
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struct blockif_elem *be, *tbe;
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off_t off;
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int i;
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be = TAILQ_FIRST(&bc->bc_freeq);
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assert(be != NULL);
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assert(be->be_status == BST_FREE);
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TAILQ_REMOVE(&bc->bc_freeq, be, be_link);
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be->be_status = BST_PEND;
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be->be_req = breq;
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be->be_op = op;
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switch (op) {
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case BOP_READ:
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case BOP_WRITE:
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case BOP_DELETE:
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off = breq->br_offset;
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for (i = 0; i < breq->br_iovcnt; i++)
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off += breq->br_iov[i].iov_len;
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break;
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default:
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off = OFF_MAX;
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}
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be->be_block = off;
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TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
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if (tbe->be_block == breq->br_offset)
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break;
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}
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if (tbe == NULL) {
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TAILQ_FOREACH(tbe, &bc->bc_busyq, be_link) {
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if (tbe->be_block == breq->br_offset)
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break;
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}
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}
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if (tbe == NULL)
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be->be_status = BST_PEND;
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else
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be->be_status = BST_BLOCK;
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TAILQ_INSERT_TAIL(&bc->bc_pendq, be, be_link);
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bc->bc_req_count++;
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return (0);
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return (be->be_status == BST_PEND);
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}
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static int
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blockif_dequeue(struct blockif_ctxt *bc, struct blockif_elem **bep)
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blockif_dequeue(struct blockif_ctxt *bc, pthread_t t, struct blockif_elem **bep)
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{
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struct blockif_elem *be;
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if (bc->bc_req_count == 0)
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return (ENOENT);
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be = TAILQ_FIRST(&bc->bc_pendq);
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assert(be != NULL);
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assert(be->be_status == BST_PEND);
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TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
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if (be->be_status == BST_PEND)
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break;
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assert(be->be_status == BST_BLOCK);
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}
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if (be == NULL)
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return (0);
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TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
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be->be_status = BST_BUSY;
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be->be_tid = bc->bc_btid;
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be->be_tid = t;
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TAILQ_INSERT_TAIL(&bc->bc_busyq, be, be_link);
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*bep = be;
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return (0);
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return (1);
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}
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static void
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blockif_complete(struct blockif_ctxt *bc, struct blockif_elem *be)
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{
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assert(be->be_status == BST_DONE);
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struct blockif_elem *tbe;
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if (be->be_status == BST_DONE || be->be_status == BST_BUSY)
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TAILQ_REMOVE(&bc->bc_busyq, be, be_link);
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else
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TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
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TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
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if (tbe->be_req->br_offset == be->be_block)
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tbe->be_status = BST_PEND;
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}
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be->be_tid = 0;
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be->be_status = BST_FREE;
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be->be_req = NULL;
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TAILQ_INSERT_TAIL(&bc->bc_freeq, be, be_link);
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bc->bc_req_count--;
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}
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static void
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@ -226,28 +253,27 @@ blockif_thr(void *arg)
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{
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struct blockif_ctxt *bc;
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struct blockif_elem *be;
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pthread_t t;
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bc = arg;
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t = pthread_self();
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for (;;) {
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pthread_mutex_lock(&bc->bc_mtx);
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while (!blockif_dequeue(bc, &be)) {
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for (;;) {
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while (blockif_dequeue(bc, t, &be)) {
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pthread_mutex_unlock(&bc->bc_mtx);
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blockif_proc(bc, be);
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pthread_mutex_lock(&bc->bc_mtx);
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blockif_complete(bc, be);
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}
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/* Check ctxt status here to see if exit requested */
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if (bc->bc_closing)
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break;
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pthread_cond_wait(&bc->bc_cond, &bc->bc_mtx);
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}
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pthread_mutex_unlock(&bc->bc_mtx);
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/*
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* Check ctxt status here to see if exit requested
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*/
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if (bc->bc_closing)
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pthread_exit(NULL);
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}
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/* Not reached */
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return (NULL);
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}
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@ -386,16 +412,16 @@ blockif_open(const char *optstr, const char *ident)
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TAILQ_INIT(&bc->bc_freeq);
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TAILQ_INIT(&bc->bc_pendq);
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TAILQ_INIT(&bc->bc_busyq);
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bc->bc_req_count = 0;
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for (i = 0; i < BLOCKIF_MAXREQ; i++) {
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bc->bc_reqs[i].be_status = BST_FREE;
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TAILQ_INSERT_HEAD(&bc->bc_freeq, &bc->bc_reqs[i], be_link);
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}
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pthread_create(&bc->bc_btid, NULL, blockif_thr, bc);
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snprintf(tname, sizeof(tname), "blk-%s", ident);
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pthread_set_name_np(bc->bc_btid, tname);
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for (i = 0; i < BLOCKIF_NUMTHR; i++) {
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pthread_create(&bc->bc_btid[i], NULL, blockif_thr, bc);
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snprintf(tname, sizeof(tname), "blk-%s-%d", ident, i);
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pthread_set_name_np(bc->bc_btid[i], tname);
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}
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return (bc);
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}
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@ -409,12 +435,12 @@ blockif_request(struct blockif_ctxt *bc, struct blockif_req *breq,
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err = 0;
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pthread_mutex_lock(&bc->bc_mtx);
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if (bc->bc_req_count < BLOCKIF_MAXREQ) {
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if (!TAILQ_EMPTY(&bc->bc_freeq)) {
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/*
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* Enqueue and inform the block i/o thread
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* that there is work available
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*/
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blockif_enqueue(bc, breq, op);
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if (blockif_enqueue(bc, breq, op))
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pthread_cond_signal(&bc->bc_cond);
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} else {
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/*
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@ -481,11 +507,7 @@ blockif_cancel(struct blockif_ctxt *bc, struct blockif_req *breq)
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/*
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* Found it.
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*/
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TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
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be->be_status = BST_FREE;
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be->be_req = NULL;
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TAILQ_INSERT_TAIL(&bc->bc_freeq, be, be_link);
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bc->bc_req_count--;
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blockif_complete(bc, be);
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pthread_mutex_unlock(&bc->bc_mtx);
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return (0);
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@ -546,7 +568,7 @@ int
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blockif_close(struct blockif_ctxt *bc)
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{
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void *jval;
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int err;
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int err, i;
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err = 0;
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@ -556,8 +578,9 @@ blockif_close(struct blockif_ctxt *bc)
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* Stop the block i/o thread
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*/
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bc->bc_closing = 1;
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pthread_cond_signal(&bc->bc_cond);
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pthread_join(bc->bc_btid, &jval);
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pthread_cond_broadcast(&bc->bc_cond);
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for (i = 0; i < BLOCKIF_NUMTHR; i++)
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pthread_join(bc->bc_btid[i], &jval);
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/* XXX Cancel queued i/o's ??? */
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