Return-Path: Received: from mx61.netapp.com ([216.240.31.181]:4582 "EHLO mx61.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933736AbeCGUnq (ORCPT ); Wed, 7 Mar 2018 15:43:46 -0500 Subject: Re: [PATCH 5/9] SUNRPC: Initialize rpc_rqst outside of xprt->reserve_lock To: Chuck Lever CC: linux-rdma , Linux NFS Mailing List References: <20180305200825.10904.40829.stgit@manet.1015granger.net> <20180305201318.10904.57825.stgit@manet.1015granger.net> <4dd8259a-e447-122b-c267-75e2e6b4714e@Netapp.com> <41538F44-115C-4F64-9BCA-0A6B8723A9F5@oracle.com> <9ac7ea34-d409-da6a-21cb-35fa6e09cd66@Netapp.com> <6C6A09E2-88A2-4968-89CD-8F6DF959B815@oracle.com> From: Anna Schumaker Message-ID: <48c31eb1-4acf-534b-57d7-7a37e5cbe3b4@Netapp.com> Date: Wed, 7 Mar 2018 15:32:58 -0500 MIME-Version: 1.0 In-Reply-To: <6C6A09E2-88A2-4968-89CD-8F6DF959B815@oracle.com> Content-Type: text/plain; charset=utf-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 03/07/2018 03:23 PM, Chuck Lever wrote: > > >> On Mar 7, 2018, at 3:00 PM, Anna Schumaker wrote: >> >> >> >> On 03/06/2018 05:30 PM, Chuck Lever wrote: >>> >>> >>>> On Mar 6, 2018, at 5:07 PM, Chuck Lever wrote: >>>> >>>> >>>> >>>>> On Mar 6, 2018, at 5:02 PM, Anna Schumaker wrote: >>>>> >>>>> Hi Chuck, >>>>> >>>>> I'm seeing a huge performance hit with this patch. I'm just running cthon over TCP, and it goes from finishing in 22 seconds to taking well over 5 minutes. I seem to only see this on the read and write tests, such as basic test5 taking a minute to finish: >>>>> >>>>> ./test5: read and write >>>>> wrote 1048576 byte file 10 times in 60.35 seconds (173737 bytes/sec) >>>>> read 1048576 byte file 10 times in 0.0 seconds (-2147483648 bytes/sec) >>>>> ./test5 ok. >>>> >>>> OK. This looks like write is impacted, but this test doesn't >>>> actually perform any reads on the wire. Try iozone with -I, >>>> maybe? That would show results for both read and write. >>> >>> Hum. >>> >>> Stock v4.16-rc4: >>> >>> ./test5: read and write >>> wrote 1048576 byte file 10 times in 0.2 seconds (350811642 bytes/sec) >>> read 1048576 byte file 10 times in 0.0 seconds (-2147483648 bytes/sec) >>> ./test5 ok. >>> >>> >>> v4.16-rc4 with my full set of patches: >>> >>> ./test5: read and write >>> wrote 1048576 byte file 10 times in 0.2 seconds (354236681 bytes/sec) >>> read 1048576 byte file 10 times in 0.0 seconds (-2147483648 bytes/sec) >>> ./test5 ok. >>> >>> I don't see a regression here. Let me know how it goes! >> >> I'm using rc4 too, so maybe it's something different in my setup? > > What is your setup, exactly? I assume your client is maybe a > single CPU guest, and the server is the same, and both are > hosted on one system? Client is single CPU kvm guest with 1 gig ram, server is also kvm on the same system with 2 cpus and 4 gigs ram. > > >> Making this change fixes the issue for me: >> >> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c >> index a394b4635f8e..273847f7e455 100644 >> --- a/net/sunrpc/xprt.c >> +++ b/net/sunrpc/xprt.c >> @@ -987,8 +987,6 @@ bool xprt_prepare_transmit(struct rpc_task *task) >> task->tk_status = -EAGAIN; >> goto out_unlock; >> } >> - if (likely(!bc_prealloc(req))) >> - req->rq_xid = xprt_alloc_xid(xprt); >> ret = true; >> out_unlock: >> spin_unlock_bh(&xprt->transport_lock); >> @@ -1315,6 +1313,7 @@ void xprt_request_init(struct rpc_task *task) >> req->rq_task = task; >> req->rq_xprt = xprt; >> req->rq_buffer = NULL; >> + req->rq_xid = xprt_alloc_xid(xprt); > > xprt_alloc_xid is just > > 1299 static inline __be32 xprt_alloc_xid(struct rpc_xprt *xprt) > 1300 { > 1301 return (__force __be32)xprt->xid++; > 1302 } > > I don't believe the new call site for xprt_request_init is > adequately serialized for this to be safe in general. That's why > I'm calling xprt_alloc_xid in xprt_prepare_transmit, behind the > transport_lock. This makes sense. > > However, I think we need to explain why that helps your performance > issue, because it doesn't make sense to me that this would make a > difference. Why did you think to try this change? Is there evidence > on the wire of XID re-use, for example? I selectively reverted parts of your original patch until I found the parts that kill my performance. > > >> req->rq_connect_cookie = xprt->connect_cookie - 1; >> req->rq_bytes_sent = 0; >> req->rq_snd_buf.len = 0; >> >> >> Anna >> >>> >>> >>>>> I haven't dug into this too deeply, but my best guess is that maybe it's due to adding a call to xprt_request_init() in net/sunrpc/clnt.c:call_reserveresult() >>>> >>>> It wasn't added there, it was moved from xprt_alloc_slot. So, >>>> it's not new work per-RPC. >>>> >>>> Any additional information would be appreciated! >>>> >>>> >>>>> Thoughts? >>>>> Anna >>>>> >>>>> On 03/05/2018 03:13 PM, Chuck Lever wrote: >>>>>> alloc_slot is a transport-specific op, but initializing an rpc_rqst >>>>>> is common to all transports. Move initialization to common code in >>>>>> preparation for adding a transport-specific alloc_slot to xprtrdma. >>>>>> >>>>>> Signed-off-by: Chuck Lever >>>>>> --- >>>>>> include/linux/sunrpc/xprt.h | 1 + >>>>>> net/sunrpc/clnt.c | 1 + >>>>>> net/sunrpc/xprt.c | 12 +++++++----- >>>>>> 3 files changed, 9 insertions(+), 5 deletions(-) >>>>>> >>>>>> diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h >>>>>> index 5fea0fb..9784e28 100644 >>>>>> --- a/include/linux/sunrpc/xprt.h >>>>>> +++ b/include/linux/sunrpc/xprt.h >>>>>> @@ -324,6 +324,7 @@ struct xprt_class { >>>>>> struct rpc_xprt *xprt_create_transport(struct xprt_create *args); >>>>>> void xprt_connect(struct rpc_task *task); >>>>>> void xprt_reserve(struct rpc_task *task); >>>>>> +void xprt_request_init(struct rpc_task *task); >>>>>> void xprt_retry_reserve(struct rpc_task *task); >>>>>> int xprt_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task); >>>>>> int xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task); >>>>>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c >>>>>> index 6e432ec..226f558 100644 >>>>>> --- a/net/sunrpc/clnt.c >>>>>> +++ b/net/sunrpc/clnt.c >>>>>> @@ -1546,6 +1546,7 @@ void rpc_force_rebind(struct rpc_clnt *clnt) >>>>>> task->tk_status = 0; >>>>>> if (status >= 0) { >>>>>> if (task->tk_rqstp) { >>>>>> + xprt_request_init(task); >>>>>> task->tk_action = call_refresh; >>>>>> return; >>>>>> } >>>>>> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c >>>>>> index 70f0050..a394b46 100644 >>>>>> --- a/net/sunrpc/xprt.c >>>>>> +++ b/net/sunrpc/xprt.c >>>>>> @@ -66,7 +66,7 @@ >>>>>> * Local functions >>>>>> */ >>>>>> static void xprt_init(struct rpc_xprt *xprt, struct net *net); >>>>>> -static void xprt_request_init(struct rpc_task *, struct rpc_xprt *); >>>>>> +static __be32 xprt_alloc_xid(struct rpc_xprt *xprt); >>>>>> static void xprt_connect_status(struct rpc_task *task); >>>>>> static int __xprt_get_cong(struct rpc_xprt *, struct rpc_task *); >>>>>> static void __xprt_put_cong(struct rpc_xprt *, struct rpc_rqst *); >>>>>> @@ -987,6 +987,8 @@ bool xprt_prepare_transmit(struct rpc_task *task) >>>>>> task->tk_status = -EAGAIN; >>>>>> goto out_unlock; >>>>>> } >>>>>> + if (likely(!bc_prealloc(req))) >>>>>> + req->rq_xid = xprt_alloc_xid(xprt); >>>>>> ret = true; >>>>>> out_unlock: >>>>>> spin_unlock_bh(&xprt->transport_lock); >>>>>> @@ -1163,10 +1165,10 @@ void xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task) >>>>>> out_init_req: >>>>>> xprt->stat.max_slots = max_t(unsigned int, xprt->stat.max_slots, >>>>>> xprt->num_reqs); >>>>>> + spin_unlock(&xprt->reserve_lock); >>>>>> + >>>>>> task->tk_status = 0; >>>>>> task->tk_rqstp = req; >>>>>> - xprt_request_init(task, xprt); >>>>>> - spin_unlock(&xprt->reserve_lock); >>>>>> } >>>>>> EXPORT_SYMBOL_GPL(xprt_alloc_slot); >>>>>> >>>>>> @@ -1303,8 +1305,9 @@ static inline void xprt_init_xid(struct rpc_xprt *xprt) >>>>>> xprt->xid = prandom_u32(); >>>>>> } >>>>>> >>>>>> -static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt) >>>>>> +void xprt_request_init(struct rpc_task *task) >>>>>> { >>>>>> + struct rpc_xprt *xprt = task->tk_xprt; >>>>>> struct rpc_rqst *req = task->tk_rqstp; >>>>>> >>>>>> INIT_LIST_HEAD(&req->rq_list); >>>>>> @@ -1312,7 +1315,6 @@ static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt) >>>>>> req->rq_task = task; >>>>>> req->rq_xprt = xprt; >>>>>> req->rq_buffer = NULL; >>>>>> - req->rq_xid = xprt_alloc_xid(xprt); >>>>>> req->rq_connect_cookie = xprt->connect_cookie - 1; >>>>>> req->rq_bytes_sent = 0; >>>>>> req->rq_snd_buf.len = 0; >>>>>> >>>> >>>> -- >>>> Chuck Lever >>>> >>>> >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >>> -- >>> Chuck Lever > > -- > Chuck Lever > > >