From patchwork Wed Aug 2 07:34:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 13337768 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BFB9C001DF for ; Wed, 2 Aug 2023 07:35:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232897AbjHBHf4 (ORCPT ); Wed, 2 Aug 2023 03:35:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232893AbjHBHfw (ORCPT ); Wed, 2 Aug 2023 03:35:52 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB409EA for ; Wed, 2 Aug 2023 00:35:24 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 7D01A21AC1; Wed, 2 Aug 2023 07:35:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1690961723; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=c75YH6ZnXDSZBOmeCiY2nx0UEGN6VJVsC99vZK/dcvU=; b=eCfJCPz8L32rwXNSmWD1BFN7rqT+Uxjik2wPyikMxGwyf5EDy5HF62yOHzCHMD2o5hp3yr XHzrfc+/B3dugE4X1kDy2zEpLuuGBK0qVzxaGfp9GQnt2UtaqraPxNVFqLwwwIIpoCMviJ PFQodOBhkkHZUwzV2NSbhU4jzVX8i/0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1690961723; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=c75YH6ZnXDSZBOmeCiY2nx0UEGN6VJVsC99vZK/dcvU=; b=f/ixDvprLjWkFpBzeVeoKVtfPDTVL6ZvvEZRMmDdcXAtkC7ASTLb+DIBL3VTHOdxoPLSaC OB1cQpY5kjSv/uCw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3725F13909; Wed, 2 Aug 2023 07:35:21 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id jsajNjkHymQsJAAAMHmgww (envelope-from ); Wed, 02 Aug 2023 07:35:21 +0000 From: NeilBrown To: Chuck Lever , Jeff Layton Cc: linux-nfs@vger.kernel.org Subject: [PATCH 5/6] SUNRPC: add list of idle threads Date: Wed, 2 Aug 2023 17:34:42 +1000 Message-Id: <20230802073443.17965-6-neilb@suse.de> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230802073443.17965-1-neilb@suse.de> References: <20230802073443.17965-1-neilb@suse.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org 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 --- include/linux/sunrpc/svc.h | 25 ++++++++++++++++++++++++- include/trace/events/sunrpc.h | 1 - net/sunrpc/svc.c | 13 ++++++++----- net/sunrpc/svc_xprt.c | 15 +++++++++++---- 4 files changed, 43 insertions(+), 11 deletions(-) diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 1ac6f74781aa..8b93af92dd53 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 1233d72714b9..dce433dea1bd 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -641,7 +641,7 @@ 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 +702,13 @@ 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 0a300ae6a7ed..e44efcc21b63 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(); try_to_freeze();