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SUNRPC: Add a server side per-connection limit 

Allow the user to limit the number of requests serviced through a single
connection, to help prevent faster clients from starving slower clients.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Trond Myklebust 2016-06-24 10:55:50 -04:00 committed by J. Bruce Fields
parent 4720b0703a
commit ff3ac5c3dc
4 changed files with 44 additions and 3 deletions
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6
Documentation/kernel-parameters.txt
View File

@ -3832,6 +3832,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
using these two parameters to set the minimum and
maximum port values.
sunrpc.svc_rpc_per_connection_limit=
[NFS,SUNRPC]
Limit the number of requests that the server will
process in parallel from a single connection.
The default value is 0 (no limit).
sunrpc.pool_mode=
[NFS]
Control how the NFS server code allocates CPUs to

1
include/linux/sunrpc/svc.h
View File

@ -268,6 +268,7 @@ struct svc_rqst {
* cache pages */
#define RQ_VICTIM (5) /* about to be shut down */
#define RQ_BUSY (6) /* request is busy */
#define RQ_DATA (7) /* request has data */
unsigned long rq_flags; /* flags field */
void * rq_argp; /* decoded arguments */

1
include/linux/sunrpc/svc_xprt.h
View File

@ -69,6 +69,7 @@ struct svc_xprt {
struct svc_serv *xpt_server; /* service for transport */
atomic_t xpt_reserved; /* space on outq that is rsvd */
atomic_t xpt_nr_rqsts; /* Number of requests */
struct mutex xpt_mutex; /* to serialize sending data */
spinlock_t xpt_lock; /* protects sk_deferred
* and xpt_auth_cache */

39
net/sunrpc/svc_xprt.c
View File

@ -21,6 +21,10 @@
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
static unsigned int svc_rpc_per_connection_limit __read_mostly;
module_param(svc_rpc_per_connection_limit, uint, 0644);
static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
static int svc_deferred_recv(struct svc_rqst *rqstp);
static struct cache_deferred_req *svc_defer(struct cache_req *req);
@ -329,12 +333,41 @@ char *svc_print_addr(struct svc_rqst *rqstp, char *buf, size_t len)
}
EXPORT_SYMBOL_GPL(svc_print_addr);
static bool svc_xprt_slots_in_range(struct svc_xprt *xprt)
{
unsigned int limit = svc_rpc_per_connection_limit;
int nrqsts = atomic_read(&xprt->xpt_nr_rqsts);
return limit == 0 || (nrqsts >= 0 && nrqsts < limit);
}
static bool svc_xprt_reserve_slot(struct svc_rqst *rqstp, struct svc_xprt *xprt)
{
if (!test_bit(RQ_DATA, &rqstp->rq_flags)) {
if (!svc_xprt_slots_in_range(xprt))
return false;
atomic_inc(&xprt->xpt_nr_rqsts);
set_bit(RQ_DATA, &rqstp->rq_flags);
}
return true;
}
static void svc_xprt_release_slot(struct svc_rqst *rqstp)
{
struct svc_xprt *xprt = rqstp->rq_xprt;
if (test_and_clear_bit(RQ_DATA, &rqstp->rq_flags)) {
atomic_dec(&xprt->xpt_nr_rqsts);
svc_xprt_enqueue(xprt);
}
}
static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt)
{
if (xprt->xpt_flags & ((1<<XPT_CONN)|(1<<XPT_CLOSE)))
return true;
if (xprt->xpt_flags & ((1<<XPT_DATA)|(1<<XPT_DEFERRED))) {
if (xprt->xpt_ops->xpo_has_wspace(xprt))
if (xprt->xpt_ops->xpo_has_wspace(xprt) &&
svc_xprt_slots_in_range(xprt))
return true;
trace_svc_xprt_no_write_space(xprt);
return false;
@ -516,8 +549,8 @@ static void svc_xprt_release(struct svc_rqst *rqstp)
rqstp->rq_res.head[0].iov_len = 0;
svc_reserve(rqstp, 0);
svc_xprt_release_slot(rqstp);
rqstp->rq_xprt = NULL;
svc_xprt_put(xprt);
}
@ -785,7 +818,7 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
svc_add_new_temp_xprt(serv, newxpt);
else
module_put(xprt->xpt_class->xcl_owner);
} else {
} else if (svc_xprt_reserve_slot(rqstp, xprt)) {
/* XPT_DATA|XPT_DEFERRED case: */
dprintk("svc: server %p, pool %u, transport %p, inuse=%d\n",
rqstp, rqstp->rq_pool->sp_id, xprt,