From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8953 invoked by alias); 21 Mar 2017 02:56:21 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 8926 invoked by uid 89); 21 Mar 2017 02:56:20 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.2 spammy=cease, 2.7.0, ipch, wait.h X-HELO: mail-pf0-f169.google.com Received: from mail-pf0-f169.google.com (HELO mail-pf0-f169.google.com) (209.85.192.169) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 21 Mar 2017 02:56:19 +0000 Received: by mail-pf0-f169.google.com with SMTP id o126so73980659pfb.3 for ; Mon, 20 Mar 2017 19:56:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=rZml/O+BgNUOUDRKiS44TuzFv+hGX9ggxbrU9R8Ek+I=; b=Qkp1DDZOpFTK3Nh1NPDYaC+WDdhPe52I/lneUiUWyMpqJuA7H0EJeiiObH8rG53P3j dBh9rVmfqaG8XIsh0FaaRW8lTkhz2JVKH9F1Ao2VaGafWJ8uUJI7rit/zvbvy9DnrTYe EpTrI1d0qfyqifrJNxngJAmVr6uk2x8cqDBmB/Xr7vV/7Syw2C1zILbBODUQG+UB25OD Cv7v9+nQHojrJ7uPWMZDpvCQ5kShXxqRPbPQTCeGHW2tIb+gUVFa6rv469mA4ykG9DgT KFz/1johQKJJCGITDM2urZkSZpNRqlafhqfKI+OzKjcSby/M1/vgXoNoV5ZLOQWQLUQ9 UUPA== X-Gm-Message-State: AFeK/H0hkNwJOLQ2e95AG+aI5/0BhcBtRONfkopPvD/NHHkzerncETvvrSia3tfGQun4jg== X-Received: by 10.98.81.132 with SMTP id f126mr8673048pfb.25.1490064978120; Mon, 20 Mar 2017 19:56:18 -0700 (PDT) Received: from tornado.leadboat.com (c-98-248-47-228.hsd1.ca.comcast.net. [98.248.47.228]) by smtp.gmail.com with ESMTPSA id u192sm8548875pgb.45.2017.03.20.19.56.16 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 20 Mar 2017 19:56:16 -0700 (PDT) Date: Tue, 21 Mar 2017 02:56:00 -0000 From: Noah Misch To: cygwin@cygwin.com Subject: Re: cygserver - Postgres Multiple connection Load Testing - Inifinte Loop Message-ID: <20170321025614.GA2100214@tornado.leadboat.com> References: <200408030333.i733XEXn023894@mx3.redhat.com> <20040803100612.GP31522@cygbert.vinschen.de> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="1yeeQ81UyVL57Vl7" Content-Disposition: inline In-Reply-To: <20040803100612.GP31522@cygbert.vinschen.de> User-Agent: Mutt/1.5.24 (2015-08-30) X-SW-Source: 2017-03/txt/msg00218.txt.bz2 --1yeeQ81UyVL57Vl7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-length: 1314 On Tue, Aug 03, 2004 at 12:06:12PM +0200, Corinna Vinschen wrote: > On Aug 2 20:33, sarbx-cygwin6344@mailblocks.com wrote: > > This time around, cygserver does not eat CPU. But after 5 to 6 > > concurrent > > connections nothing seem to work, looks kind of hung. There is no > > activity in the Postgres > > log file. Opening a new database connection also hangs. There is no > > activity on the machine. > Any chance to create a simple testcase which uncovers that behaviour > without involving a whole database system? Attached test program reproduces it on Cygwin 2.7.0, Cygwin 1.7.5, and a few intermediate versions. The program creates sixteen processes that each perform a tight loop over the following: - select one of four semaphores - reduce semaphore's value from 1 to 0 ("lock" it) - raise semaphore's value from 0 to 1 ("unlock" it) On GNU/Linux, AIX, and Solaris, the processes keep busy and finish one million lock/unlock cycles apiece in a few minutes. On Cygwin, they hang within a few seconds and under one hundred cycles apiece. At that point, cygserver is unresponsive to other clients; for example, "strace /bin/true", opening a new Cygwin terminal, "cat /proc/sysvipc/sem" and "cygserver -S" all hang. In most tests, cygserver was not consuming CPU while unresponsive. Thanks, nm --1yeeQ81UyVL57Vl7 Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="sema_parallel.c" Content-length: 2344 /* * Demonstrate cygserver hang under concurrent sysv semaphore traffic. Run * without arguments. Output will cease within a few seconds, and cygserver * will be unresponsive to all clients. * * This is compatible with default cygserver settings; it uses a single * semaphore set of four semaphores. */ #include #include #include #include #include #include #include #include #define SEM_KEY 0x631a2c3e #define N_WORKER 16 #define N_SEMA (N_WORKER/4) #define N_CYCLE 1000000 union semun { int val; struct semid_ds *buf; unsigned short *array; }; static int print_every = 1; /* In parallel, N_WORKER processes run this function. */ static int do_worker(int ordinal, int set) { int i; struct sembuf op; printf("start worker %d\n", ordinal); fflush(stdout); op.sem_flg = 0; for (i = 1; i <= N_CYCLE; i++) { op.sem_num = random() % N_SEMA; op.sem_op = -1; if (0 > semop(set, &op, 1)) { perror("semop"); return 1; } op.sem_op = 1; if (0 > semop(set, &op, 1)) { perror("semop"); return 1; } if (i % print_every == 0) { printf("worker %d: %d cycles elapsed\n", ordinal, i); fflush(stdout); } } return 0; } int main(int argc, char **argv) { int status = 1, set, i, child_status; if (argc == 2) print_every = atoi(argv[1]); else if (argc != 1) { fprintf(stderr, "Usage: sema_parallel [print-every-N]\n"); return status; } puts("semget"); fflush(stdout); set = semget(SEM_KEY, N_SEMA, IPC_CREAT | 0600); if (set == -1) { perror("semget"); return status; } puts("SETVAL"); fflush(stdout); for (i = 0; i < N_SEMA; i++) { union semun s; s.val = 1; if (0 > semctl(set, i, SETVAL, s)) { perror("semctl(SETVAL)"); goto cleanup; } } for (i = 0; i < N_WORKER; i++) { pid_t pid; pid = fork(); switch (pid) { case -1: perror("fork"); goto cleanup; case 0: return do_worker(i, set); } } status = 0; cleanup: while (wait(&child_status) != -1) ; if (errno != ECHILD) { perror("wait"); status = 1; } if (0 > semctl(set, 0, IPC_RMID)) { perror("semtctl(IPC_RMID)"); status = 1; } return status; } --1yeeQ81UyVL57Vl7 Content-Type: text/plain; charset=us-ascii Content-length: 219 -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple --1yeeQ81UyVL57Vl7--