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Diffstat (limited to 'lib/clplumbing/cpulimits.c')
| -rw-r--r-- | lib/clplumbing/cpulimits.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/lib/clplumbing/cpulimits.c b/lib/clplumbing/cpulimits.c new file mode 100644 index 0000000..4c03f23 --- /dev/null +++ b/lib/clplumbing/cpulimits.c @@ -0,0 +1,219 @@ +/* + * Functions to put dynamic limits on CPU consumption. + * + * Copyright (C) 2003 IBM Corporation + * + * Author: <alanr@unix.sh> + * + * This software licensed under the GNU LGPL. + * + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of version 2.1 of the GNU Lesser General Public + * License as published by the Free Software Foundation. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + * + ************************************************************************** + * + * This allows us to better catch runaway realtime processes that + * might otherwise hang the whole system (if they're POSIX realtime + * processes). + * + * We do this by getting a "lease" on CPU time, and then extending + * the lease every so often as real time elapses. Since we only + * extend the lease by a bounded amount computed on the basis of an + * upper bound of how much CPU the code is "expected" to consume during + * the lease interval, this means that if we go into an infinite + * loop, it is highly probable that this will be detected and our + * process will be terminated by the operating system with a SIGXCPU. + * + * If you want to handle this signal, then fine... Do so... + * + * If not, the default is to terminate the process and produce a core + * dump. This is a great default for debugging... + * + * + * The process is basically this: + * - Set the CPU percentage limit with cl_cpu_limit_setpercent() + * according to what you expect the CPU percentage to top out at + * measured over an interval at >= 60 seconds + * - Call cl_cpu_limit_ms_interval() to figure out how often to update + * the CPU limit (it returns milliseconds) + * - At least as often as indicated above, call cl_cpu_limit_update() + * to update our current CPU limit. + * + * These limits are approximate, so be a little conservative. + * If you've gone into an infinite loop, it'll likely get caught ;-) + * + * As of this writing, this code will never set the soft CPU limit less + * than four seconds, or greater than 60 seconds. + * + */ +#include <lha_internal.h> +#include <sys/time.h> +#include <sys/resource.h> +#include <clplumbing/longclock.h> +#include <unistd.h> +#include <clplumbing/cpulimits.h> +#include <clplumbing/cl_log.h> + +static longclock_t nexttimetoupdate; + +/* How long between checking out CPU usage? */ +static int cpuinterval_ms = 0; + +/* How much cpu (in seconds) allowed at each check interval? */ +static int cpusecs; + +#define ROUND(foo) ((int)((foo)+0.5)) + + +/* + * Update our current CPU limit (via setrlimit) according to our + * current resource consumption, and our current cpu % limit + * + * We only set the soft CPU limit, and do not change the maximum + * (hard) CPU limit, but we respect it if it's already set. + * + * As a result, this code can be used by privileged and non-privileged + * processes. + */ + +static int +update_cpu_interval(void) +{ + struct rusage ru; + struct rlimit rlim; + unsigned long timesecs; + unsigned long microsec; + + /* Compute how much CPU we've used so far... */ + + getrusage(RUSAGE_SELF, &ru); + timesecs = ru.ru_utime.tv_sec + ru.ru_stime.tv_sec; + microsec = ru.ru_utime.tv_usec + ru.ru_stime.tv_usec; + + /* Round up to the next higher second */ + if (microsec > 1000000) { + timesecs += 2; + }else{ + timesecs += 1; + } + + /* Compute our next CPU limit */ + timesecs += cpusecs; + + /* Figure out when we next need to update our CPU limit */ + nexttimetoupdate = add_longclock(time_longclock() + , msto_longclock(cpuinterval_ms)); + + getrlimit(RLIMIT_CPU, &rlim); + + /* Make sure we don't exceed the hard CPU limit (if set) */ + if (rlim.rlim_max != RLIM_INFINITY && timesecs > rlim.rlim_max) { + timesecs = rlim.rlim_max; + } +#if 0 + cl_log(LOG_DEBUG + , "Setting max CPU limit to %ld seconds", timesecs); +#endif + + /* Update the OS-level soft CPU limit */ + rlim.rlim_cur = timesecs; + return setrlimit(RLIMIT_CPU, &rlim); +} + +#define MININTERVAL 60 /* seconds */ + +int +cl_cpu_limit_setpercent(int ipercent) +{ + float percent; + int interval; + + if (ipercent > 99) { + ipercent = 99; + } + if (ipercent < 1) { + ipercent = 1; + } + percent = ipercent; + percent /= (float)100; + + interval= MININTERVAL; + + /* + * Compute how much CPU we will allow to be used + * for each check interval. + * + * Rules: + * - we won't require checking more often than + * every 60 seconds + * - we won't limit ourselves to less than + * 4 seconds of CPU per checking interval + */ + for (;;) { + cpusecs = ROUND((float)interval*percent); + if (cpusecs >= 4) { + break; + } + interval *= 2; + } + + /* + * Now compute how long to go between updates to our CPU limit + * from the perspective of the OS (via setrlimit(2)). + * + * We do the computation this way because the CPU limit + * can only be set to the nearest second, but timers can + * generally be set more accurately. + */ + cpuinterval_ms = (int)(((float)cpusecs / percent)*1000.0); + + cl_log(LOG_DEBUG + , "Limiting CPU: %d CPU seconds every %d milliseconds" + , cpusecs, cpuinterval_ms); + + return update_cpu_interval(); +} + +int +cl_cpu_limit_ms_interval(void) +{ + return cpuinterval_ms; +} + +int +cl_cpu_limit_update(void) +{ + longclock_t now = time_longclock(); + long msleft; + + if (cpuinterval_ms <= 0) { + return 0; + } + if (cmp_longclock(now, nexttimetoupdate) > 0) { + return update_cpu_interval(); + } + msleft = longclockto_ms(sub_longclock(nexttimetoupdate, now)); + if (msleft < 500) { + return update_cpu_interval(); + } + return 0; +} +int +cl_cpu_limit_disable(void) +{ + struct rlimit rlim; + getrlimit(RLIMIT_CPU, &rlim); + rlim.rlim_cur = rlim.rlim_max; + return setrlimit(RLIMIT_CPU, &rlim); +} |