From 1c87a0c39a860e19eee41815737e38b2a035c040 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 6 Jan 2026 13:59:49 -0500 Subject: [PATCH] nfsd: adjust number of running nfsd threads based on activity nfsd() is changed to pass a timeout to svc_recv() when there is a min number of threads set, and to handle error returns from it: In the case of -ETIMEDOUT, if the service mutex can be taken (via trylock), the thread becomes an RQ_VICTIM so that it will exit, providing that the actual number of threads is above pool->sp_nrthrmin. In the case of -EBUSY, if the actual number of threads is below pool->sp_nrthrmax, it will attempt to start a new thread. This attempt is gated on a new SP_TASK_STARTING pool flag that serializes thread creation attempts within a pool, and further by mutex_trylock(). Neil says: "I think we want memory pressure to be able to push a thread into returning -ETIMEDOUT. That can come later." Signed-off-by: NeilBrown Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/nfssvc.c | 43 ++++++++++++++++++++++++++++++++++++++++++- fs/nfsd/trace.h | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 77 insertions(+), 1 deletion(-) diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index e3f647efc4c7b..1e2570e3c754c 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -882,9 +882,11 @@ static int nfsd(void *vrqstp) { struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp; + struct svc_pool *pool = rqstp->rq_pool; struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list); struct net *net = perm_sock->xpt_net; struct nfsd_net *nn = net_generic(net, nfsd_net_id); + bool have_mutex = false; /* At this point, the thread shares current->fs * with the init process. We need to create files with the @@ -902,7 +904,44 @@ nfsd(void *vrqstp) * The main request loop */ while (!svc_thread_should_stop(rqstp)) { - svc_recv(rqstp, 0); + switch (svc_recv(rqstp, 5 * HZ)) { + case -ETIMEDOUT: + /* No work arrived within the timeout window */ + if (mutex_trylock(&nfsd_mutex)) { + if (pool->sp_nrthreads > pool->sp_nrthrmin) { + trace_nfsd_dynthread_kill(net, pool); + set_bit(RQ_VICTIM, &rqstp->rq_flags); + have_mutex = true; + } else { + mutex_unlock(&nfsd_mutex); + } + } else { + trace_nfsd_dynthread_trylock_fail(net, pool); + } + break; + case -EBUSY: + /* No idle threads; consider spawning another */ + if (pool->sp_nrthreads < pool->sp_nrthrmax) { + if (mutex_trylock(&nfsd_mutex)) { + if (pool->sp_nrthreads < pool->sp_nrthrmax) { + int ret; + + trace_nfsd_dynthread_start(net, pool); + ret = svc_new_thread(rqstp->rq_server, pool); + if (ret) + pr_notice_ratelimited("%s: unable to spawn new thread: %d\n", + __func__, ret); + } + mutex_unlock(&nfsd_mutex); + } else { + trace_nfsd_dynthread_trylock_fail(net, pool); + } + } + clear_bit(SP_TASK_STARTING, &pool->sp_flags); + break; + default: + break; + } nfsd_file_net_dispose(nn); } @@ -910,6 +949,8 @@ nfsd(void *vrqstp) /* Release the thread */ svc_exit_thread(rqstp); + if (have_mutex) + mutex_unlock(&nfsd_mutex); return 0; } diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h index 5ae2a611e57f4..8885fd9bead98 100644 --- a/fs/nfsd/trace.h +++ b/fs/nfsd/trace.h @@ -91,6 +91,41 @@ DEFINE_EVENT(nfsd_xdr_err_class, nfsd_##name##_err, \ DEFINE_NFSD_XDR_ERR_EVENT(garbage_args); DEFINE_NFSD_XDR_ERR_EVENT(cant_encode); +DECLARE_EVENT_CLASS(nfsd_dynthread_class, + TP_PROTO( + const struct net *net, + const struct svc_pool *pool + ), + TP_ARGS(net, pool), + TP_STRUCT__entry( + __field(unsigned int, netns_ino) + __field(unsigned int, pool_id) + __field(unsigned int, nrthreads) + __field(unsigned int, nrthrmin) + __field(unsigned int, nrthrmax) + ), + TP_fast_assign( + __entry->netns_ino = net->ns.inum; + __entry->pool_id = pool->sp_id; + __entry->nrthreads = pool->sp_nrthreads; + __entry->nrthrmin = pool->sp_nrthrmin; + __entry->nrthrmax = pool->sp_nrthrmax; + ), + TP_printk("pool=%u nrthreads=%u nrthrmin=%u nrthrmax=%u", + __entry->pool_id, __entry->nrthreads, + __entry->nrthrmin, __entry->nrthrmax + ) +); + +#define DEFINE_NFSD_DYNTHREAD_EVENT(name) \ +DEFINE_EVENT(nfsd_dynthread_class, nfsd_dynthread_##name, \ + TP_PROTO(const struct net *net, const struct svc_pool *pool), \ + TP_ARGS(net, pool)) + +DEFINE_NFSD_DYNTHREAD_EVENT(start); +DEFINE_NFSD_DYNTHREAD_EVENT(kill); +DEFINE_NFSD_DYNTHREAD_EVENT(trylock_fail); + #define show_nfsd_may_flags(x) \ __print_flags(x, "|", \ { NFSD_MAY_EXEC, "EXEC" }, \ -- 2.47.3