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sdnvme: handle machines with more cpu's than submit queues (thanks mischief)

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We used to assume a 1:1 pairing of processors to submit queues.
With recent machines, we now got more cpu cores than what some
nvme drives support so we need to distribute the queues across
these cpu's which requires locking on command submission.

There is a feature get/set command to probe the number of submit
and completion queues, but we decided to just handling
submission queue create command error gracefully as it is simpler
and has less chance of regression with existing setups.

Thanks to mischief for investigating and writing the code.
This commit is contained in:
cinap_lenrek 2020-10-18 02:51:32 +02:00
parent 5fd2e746e1
commit cf8ff0e713
1 changed files with 25 additions and 5 deletions
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30
sys/src/9/pc/sdnvme.c
View file

@ -41,6 +41,7 @@ struct SQ
u32int *base;
WS **wait;
Ctlr *ctlr;
Lock;
};
struct Ctlr
@ -63,6 +64,8 @@ struct Ctlr
u32int mpsshift;
u32int dstrd;
u32int nsq;
CQ cq[1+1];
SQ sq[1+MAXMACH];
@ -99,7 +102,9 @@ qcmd(WS *ws, Ctlr *ctlr, int adm, u32int opc, u32int nsid, void *mptr, void *dat
if(!adm){
Retry:
splhi();
sq = &ctlr->sq[1+m->machno];
sq = &ctlr->sq[1+(m->machno % ctlr->nsq)];
if(conf.nmach > ctlr->nsq)
lock(sq);
} else {
qlock(ctlr);
sq = &ctlr->sq[0];
@ -207,7 +212,9 @@ wcmd(WS *ws)
coherence();
ctlr->reg[DBell + ((sq-ctlr->sq)*2+0 << ctlr->dstrd)] = sq->tail & sq->mask;
if(sq > ctlr->sq) {
assert(sq == &ctlr->sq[1+m->machno]);
assert(sq == &ctlr->sq[1+(m->machno % ctlr->nsq)]);
if(conf.nmach > ctlr->nsq)
unlock(sq);
spllo();
} else
qunlock(sq->ctlr);
@ -381,7 +388,7 @@ sqalloc(Ctlr *ctlr, SQ *sq, u32int lgsize)
static void
setupqueues(Ctlr *ctlr)
{
u32int lgsize, *e;
u32int lgsize, st, *e;
CQ *cq;
SQ *sq;
WS ws;
@ -400,6 +407,8 @@ setupqueues(Ctlr *ctlr)
e[11] = 3; /* IEN | PC */
checkstatus(wcmd(&ws), "create completion queue");
st = 0;
/* SQID[1..nmach]: submission queue per cpu */
for(i=1; i<=conf.nmach; i++){
sq = &ctlr->sq[i];
@ -407,8 +416,19 @@ setupqueues(Ctlr *ctlr)
e = qcmd(&ws, ctlr, 1, 0x01, 0, nil, sq->base, 0x1000);
e[10] = i | sq->mask<<16;
e[11] = (cq - ctlr->cq)<<16 | 1; /* CQID<<16 | PC */
checkstatus(wcmd(&ws), "create submission queue");
st = wcmd(&ws);
if(st != 0){
free(sq->base);
free(sq->wait);
memset(sq, 0, sizeof(*sq));
break;
}
}
ctlr->nsq = i - 1;
if(ctlr->nsq < 1)
checkstatus(st, "create submission queues");
ilock(&ctlr->intr);
ctlr->ints |= 1<<(cq - ctlr->cq);
@ -544,7 +564,7 @@ nvmeenable(SDev *sd)
Ready:
identify(ctlr);
setupqueues(ctlr);
print("%s: using %d submit queues\n", name, ctlr->nsq);
poperror();
return 1;