Return-Path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:42448 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751914AbZEMDuV (ORCPT ); Tue, 12 May 2009 23:50:21 -0400 Date: Tue, 12 May 2009 20:44:33 -0700 From: Andrew Morton To: Jeff Moyer Cc: Jens Axboe , linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Olga Kornievskaia , "J. Bruce Fields" , Jim Rees , linux-nfs@vger.kernel.org Subject: Re: 2.6.30-rc deadline scheduler performance regression for iozone over NFS Message-Id: <20090512204433.7eb69075.akpm@linux-foundation.org> In-Reply-To: References: <20090508120119.8c93cfd7.akpm@linux-foundation.org> <20090511081415.GL4694@kernel.dk> <20090511165826.GG4694@kernel.dk> Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 (obvious cc's added...) It's an iozone performance regression. On Tue, 12 May 2009 23:29:30 -0400 Jeff Moyer wrote: > Jens Axboe writes: > > > On Mon, May 11 2009, Jeff Moyer wrote: > >> Jens Axboe writes: > >> > >> > On Fri, May 08 2009, Andrew Morton wrote: > >> >> On Thu, 23 Apr 2009 10:01:58 -0400 > >> >> Jeff Moyer wrote: > >> >> > >> >> > Hi, > >> >> > > >> >> > I've been working on CFQ improvements for interleaved I/Os between > >> >> > processes, and noticed a regression in performance when using the > >> >> > deadline I/O scheduler. The test uses a server configured with a cciss > >> >> > array and 1Gb/s ethernet. > >> >> > > >> >> > The iozone command line was: > >> >> > iozone -s 2000000 -r 64 -f /mnt/test/testfile -i 1 -w > >> >> > > >> >> > The numbers in the nfsd's row represent the number of nfsd "threads". > >> >> > These numbers (in MB/s) represent the average of 5 runs. > >> >> > > >> >> > v2.6.29 > >> >> > > >> >> > nfsd's | 1 | 2 | 4 | 8 > >> >> > --------+---------------+-------+------ > >> >> > deadline| 43207 | 67436 | 96289 | 107590 > >> >> > > >> >> > 2.6.30-rc1 > >> >> > > >> >> > nfsd's | 1 | 2 | 4 | 8 > >> >> > --------+---------------+-------+------ > >> >> > deadline| 43732 | 68059 | 76659 | 83231 > >> >> > > >> >> > 2.6.30-rc3.block-for-linus > >> >> > > >> >> > nfsd's | 1 | 2 | 4 | 8 > >> >> > --------+---------------+-------+------ > >> >> > deadline| 46102 | 71151 | 83120 | 82330 > >> >> > > >> >> > > >> >> > Notice the drop for 4 and 8 threads. It may be worth noting that the > >> >> > default number of NFSD threads is 8. > >> >> > > >> >> > >> >> I guess we should ask Rafael to add this to the post-2.6.29 regression > >> >> list. > >> > > >> > I agree. It'd be nice to bisect this one down, I'm guessing some mm > >> > change has caused this writeout regression. > >> > >> It's not writeout, it's a read test. > > > > Doh sorry, I even ran these tests as well a few weeks back. So perhaps > > some read-ahead change, I didn't look into it. FWIW, on a single SATA > > drive here, it didn't show any difference. > > OK, I bisected this to the following commit. The mount is done using > NFSv3, by the way. > > commit 47a14ef1af48c696b214ac168f056ddc79793d0e > Author: Olga Kornievskaia > Date: Tue Oct 21 14:13:47 2008 -0400 > > svcrpc: take advantage of tcp autotuning > > Allow the NFSv4 server to make use of TCP autotuning behaviour, which > was previously disabled by setting the sk_userlocks variable. > > Set the receive buffers to be big enough to receive the whole RPC > request, and set this for the listening socket, not the accept socket. > > Remove the code that readjusts the receive/send buffer sizes for the > accepted socket. Previously this code was used to influence the TCP > window management behaviour, which is no longer needed when autotuning > is enabled. > > This can improve IO bandwidth on networks with high bandwidth-delay > products, where a large tcp window is required. It also simplifies > performance tuning, since getting adequate tcp buffers previously > required increasing the number of nfsd threads. > > Signed-off-by: Olga Kornievskaia > Cc: Jim Rees > Signed-off-by: J. Bruce Fields > > diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c > index 5763e64..7a2a90f 100644 > --- a/net/sunrpc/svcsock.c > +++ b/net/sunrpc/svcsock.c > @@ -345,7 +345,6 @@ static void svc_sock_setbufsize(struct socket *sock, unsigned int snd, > lock_sock(sock->sk); > sock->sk->sk_sndbuf = snd * 2; > sock->sk->sk_rcvbuf = rcv * 2; > - sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK|SOCK_RCVBUF_LOCK; > release_sock(sock->sk); > #endif > } > @@ -797,23 +796,6 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp) > test_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags), > test_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags)); > > - if (test_and_clear_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags)) > - /* sndbuf needs to have room for one request > - * per thread, otherwise we can stall even when the > - * network isn't a bottleneck. > - * > - * We count all threads rather than threads in a > - * particular pool, which provides an upper bound > - * on the number of threads which will access the socket. > - * > - * rcvbuf just needs to be able to hold a few requests. > - * Normally they will be removed from the queue > - * as soon a a complete request arrives. > - */ > - svc_sock_setbufsize(svsk->sk_sock, > - (serv->sv_nrthreads+3) * serv->sv_max_mesg, > - 3 * serv->sv_max_mesg); > - > clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); > > /* Receive data. If we haven't got the record length yet, get > @@ -1061,15 +1043,6 @@ static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv) > > tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF; > > - /* initialise setting must have enough space to > - * receive and respond to one request. > - * svc_tcp_recvfrom will re-adjust if necessary > - */ > - svc_sock_setbufsize(svsk->sk_sock, > - 3 * svsk->sk_xprt.xpt_server->sv_max_mesg, > - 3 * svsk->sk_xprt.xpt_server->sv_max_mesg); > - > - set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags); > set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); > if (sk->sk_state != TCP_ESTABLISHED) > set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags); > @@ -1140,8 +1113,14 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv, > /* Initialize the socket */ > if (sock->type == SOCK_DGRAM) > svc_udp_init(svsk, serv); > - else > + else { > + /* initialise setting must have enough space to > + * receive and respond to one request. > + */ > + svc_sock_setbufsize(svsk->sk_sock, 4 * serv->sv_max_mesg, > + 4 * serv->sv_max_mesg); > svc_tcp_init(svsk, serv); > + } > > /* > * We start one listener per sv_serv. We want AF_INET