From 5ff817b23534dd3942f881ab01dd5050505517aa Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 11 Sep 2023 10:39:11 -0400 Subject: SUNRPC: add list of idle threads Rather than searching a list of threads to find an idle one, having a list of idle threads allows an idle thread to be found immediately. This adds some spin_lock calls which is not ideal, but as the hold-time is tiny it is still faster than searching a list. A future patch will remove them using llist.h. This involves some subtlety and so is left to a separate patch. This removes the need for the RQ_BUSY flag. The rqst is "busy" precisely when it is not on the "idle" list. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever --- include/linux/sunrpc/svc.h | 25 ++++++++++++++++++++++++- include/trace/events/sunrpc.h | 1 - net/sunrpc/svc.c | 14 +++++++++----- net/sunrpc/svc_xprt.c | 15 +++++++++++---- 4 files changed, 44 insertions(+), 11 deletions(-) diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 0ec691070e27..e9c34e99bc88 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -37,6 +37,7 @@ struct svc_pool { struct list_head sp_sockets; /* pending sockets */ unsigned int sp_nrthreads; /* # of threads in pool */ struct list_head sp_all_threads; /* all server threads */ + struct list_head sp_idle_threads; /* idle server threads */ /* statistics on pool operation */ struct percpu_counter sp_messages_arrived; @@ -186,6 +187,7 @@ extern u32 svc_max_payload(const struct svc_rqst *rqstp); */ struct svc_rqst { struct list_head rq_all; /* all threads list */ + struct list_head rq_idle; /* On the idle list */ struct rcu_head rq_rcu_head; /* for RCU deferred kfree */ struct svc_xprt * rq_xprt; /* transport ptr */ @@ -262,10 +264,31 @@ enum { RQ_SPLICE_OK, /* turned off in gss privacy to prevent * encrypting page cache pages */ RQ_VICTIM, /* Have agreed to shut down */ - RQ_BUSY, /* request is busy */ RQ_DATA, /* request has data */ }; +/** + * svc_thread_set_busy - mark a thread as busy + * @rqstp: the thread which is now busy + * + * If rq_idle is "empty", the thread must be busy. + */ +static inline void svc_thread_set_busy(struct svc_rqst *rqstp) +{ + INIT_LIST_HEAD(&rqstp->rq_idle); +} + +/** + * svc_thread_busy - check if a thread as busy + * @rqstp: the thread which might be busy + * + * If rq_idle is "empty", the thread must be busy. + */ +static inline bool svc_thread_busy(struct svc_rqst *rqstp) +{ + return list_empty(&rqstp->rq_idle); +} + #define SVC_NET(rqst) (rqst->rq_xprt ? rqst->rq_xprt->xpt_net : rqst->rq_bc_net) /* diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h index 6beb38c1dcb5..337c90787fb1 100644 --- a/include/trace/events/sunrpc.h +++ b/include/trace/events/sunrpc.h @@ -1677,7 +1677,6 @@ DEFINE_SVCXDRBUF_EVENT(sendto); svc_rqst_flag(DROPME) \ svc_rqst_flag(SPLICE_OK) \ svc_rqst_flag(VICTIM) \ - svc_rqst_flag(BUSY) \ svc_rqst_flag_end(DATA) #undef svc_rqst_flag diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index db579bbc0a0a..9d080fe2dcdf 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -510,6 +510,7 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools, pool->sp_id = i; INIT_LIST_HEAD(&pool->sp_sockets); INIT_LIST_HEAD(&pool->sp_all_threads); + INIT_LIST_HEAD(&pool->sp_idle_threads); spin_lock_init(&pool->sp_lock); percpu_counter_init(&pool->sp_messages_arrived, 0, GFP_KERNEL); @@ -641,7 +642,7 @@ svc_rqst_alloc(struct svc_serv *serv, struct svc_pool *pool, int node) folio_batch_init(&rqstp->rq_fbatch); - __set_bit(RQ_BUSY, &rqstp->rq_flags); + svc_thread_set_busy(rqstp); rqstp->rq_server = serv; rqstp->rq_pool = pool; @@ -702,10 +703,13 @@ void svc_pool_wake_idle_thread(struct svc_pool *pool) struct svc_rqst *rqstp; rcu_read_lock(); - list_for_each_entry_rcu(rqstp, &pool->sp_all_threads, rq_all) { - if (test_and_set_bit(RQ_BUSY, &rqstp->rq_flags)) - continue; - + spin_lock_bh(&pool->sp_lock); + rqstp = list_first_entry_or_null(&pool->sp_idle_threads, + struct svc_rqst, rq_idle); + if (rqstp) + list_del_init(&rqstp->rq_idle); + spin_unlock_bh(&pool->sp_lock); + if (rqstp) { WRITE_ONCE(rqstp->rq_qtime, ktime_get()); wake_up_process(rqstp->rq_task); rcu_read_unlock(); diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index b8539545fefd..ebfeeb504a79 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -737,8 +737,9 @@ static void svc_rqst_wait_for_work(struct svc_rqst *rqstp) set_current_state(TASK_IDLE); smp_mb__before_atomic(); clear_bit(SP_CONGESTED, &pool->sp_flags); - clear_bit(RQ_BUSY, &rqstp->rq_flags); - smp_mb__after_atomic(); + spin_lock_bh(&pool->sp_lock); + list_add(&rqstp->rq_idle, &pool->sp_idle_threads); + spin_unlock_bh(&pool->sp_lock); /* Need to check should_sleep() again after * setting task state in case a wakeup happened @@ -751,8 +752,14 @@ static void svc_rqst_wait_for_work(struct svc_rqst *rqstp) cond_resched(); } - set_bit(RQ_BUSY, &rqstp->rq_flags); - smp_mb__after_atomic(); + /* We *must* be removed from the list before we can continue. + * If we were woken, this is already done + */ + if (!svc_thread_busy(rqstp)) { + spin_lock_bh(&pool->sp_lock); + list_del_init(&rqstp->rq_idle); + spin_unlock_bh(&pool->sp_lock); + } } else { cond_resched(); } -- cgit v1.2.3