sched_4bsd.c revision 107135
1/*- 2 * Copyright (c) 1982, 1986, 1990, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * $FreeBSD: head/sys/kern/sched_4bsd.c 107135 2002-11-21 09:14:13Z jeff $ 39 */ 40 41#include <sys/param.h> 42#include <sys/systm.h> 43#include <sys/kernel.h> 44#include <sys/ktr.h> 45#include <sys/lock.h> 46#include <sys/mutex.h> 47#include <sys/proc.h> 48#include <sys/resourcevar.h> 49#include <sys/sched.h> 50#include <sys/smp.h> 51#include <sys/sysctl.h> 52#include <sys/sx.h> 53 54/* 55 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in 56 * the range 100-256 Hz (approximately). 57 */ 58#define ESTCPULIM(e) \ 59 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \ 60 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1) 61#define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */ 62#define NICE_WEIGHT 1 /* Priorities per nice level. */ 63 64struct ke_sched *kse0_sched = NULL; 65struct kg_sched *ksegrp0_sched = NULL; 66struct p_sched *proc0_sched = NULL; 67struct td_sched *thread0_sched = NULL; 68 69static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */ 70#define SCHED_QUANTUM (hz / 10); /* Default sched quantum */ 71 72static struct callout schedcpu_callout; 73static struct callout roundrobin_callout; 74 75static void roundrobin(void *arg); 76static void schedcpu(void *arg); 77static void sched_setup(void *dummy); 78static void maybe_resched(struct thread *td); 79static void updatepri(struct ksegrp *kg); 80static void resetpriority(struct ksegrp *kg); 81 82SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 83 84/* 85 * Global run queue. 86 */ 87static struct runq runq; 88SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq) 89 90static int 91sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 92{ 93 int error, new_val; 94 95 new_val = sched_quantum * tick; 96 error = sysctl_handle_int(oidp, &new_val, 0, req); 97 if (error != 0 || req->newptr == NULL) 98 return (error); 99 if (new_val < tick) 100 return (EINVAL); 101 sched_quantum = new_val / tick; 102 hogticks = 2 * sched_quantum; 103 return (0); 104} 105 106SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW, 107 0, sizeof sched_quantum, sysctl_kern_quantum, "I", 108 "Roundrobin scheduling quantum in microseconds"); 109 110/* 111 * Arrange to reschedule if necessary, taking the priorities and 112 * schedulers into account. 113 */ 114static void 115maybe_resched(struct thread *td) 116{ 117 118 mtx_assert(&sched_lock, MA_OWNED); 119 if (td->td_priority < curthread->td_priority) 120 curthread->td_kse->ke_flags |= KEF_NEEDRESCHED; 121} 122 123/* 124 * Force switch among equal priority processes every 100ms. 125 * We don't actually need to force a context switch of the current process. 126 * The act of firing the event triggers a context switch to softclock() and 127 * then switching back out again which is equivalent to a preemption, thus 128 * no further work is needed on the local CPU. 129 */ 130/* ARGSUSED */ 131static void 132roundrobin(void *arg) 133{ 134 135#ifdef SMP 136 mtx_lock_spin(&sched_lock); 137 forward_roundrobin(); 138 mtx_unlock_spin(&sched_lock); 139#endif 140 141 callout_reset(&roundrobin_callout, sched_quantum, roundrobin, NULL); 142} 143 144/* 145 * Constants for digital decay and forget: 146 * 90% of (p_estcpu) usage in 5 * loadav time 147 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 148 * Note that, as ps(1) mentions, this can let percentages 149 * total over 100% (I've seen 137.9% for 3 processes). 150 * 151 * Note that schedclock() updates p_estcpu and p_cpticks asynchronously. 152 * 153 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. 154 * That is, the system wants to compute a value of decay such 155 * that the following for loop: 156 * for (i = 0; i < (5 * loadavg); i++) 157 * p_estcpu *= decay; 158 * will compute 159 * p_estcpu *= 0.1; 160 * for all values of loadavg: 161 * 162 * Mathematically this loop can be expressed by saying: 163 * decay ** (5 * loadavg) ~= .1 164 * 165 * The system computes decay as: 166 * decay = (2 * loadavg) / (2 * loadavg + 1) 167 * 168 * We wish to prove that the system's computation of decay 169 * will always fulfill the equation: 170 * decay ** (5 * loadavg) ~= .1 171 * 172 * If we compute b as: 173 * b = 2 * loadavg 174 * then 175 * decay = b / (b + 1) 176 * 177 * We now need to prove two things: 178 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 179 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 180 * 181 * Facts: 182 * For x close to zero, exp(x) =~ 1 + x, since 183 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 184 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 185 * For x close to zero, ln(1+x) =~ x, since 186 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 187 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 188 * ln(.1) =~ -2.30 189 * 190 * Proof of (1): 191 * Solve (factor)**(power) =~ .1 given power (5*loadav): 192 * solving for factor, 193 * ln(factor) =~ (-2.30/5*loadav), or 194 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 195 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 196 * 197 * Proof of (2): 198 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 199 * solving for power, 200 * power*ln(b/(b+1)) =~ -2.30, or 201 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 202 * 203 * Actual power values for the implemented algorithm are as follows: 204 * loadav: 1 2 3 4 205 * power: 5.68 10.32 14.94 19.55 206 */ 207 208/* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 209#define loadfactor(loadav) (2 * (loadav)) 210#define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 211 212/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 213static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 214SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 215 216/* 217 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 218 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 219 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 220 * 221 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 222 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 223 * 224 * If you don't want to bother with the faster/more-accurate formula, you 225 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 226 * (more general) method of calculating the %age of CPU used by a process. 227 */ 228#define CCPU_SHIFT 11 229 230/* 231 * Recompute process priorities, every hz ticks. 232 * MP-safe, called without the Giant mutex. 233 */ 234/* ARGSUSED */ 235static void 236schedcpu(void *arg) 237{ 238 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 239 struct thread *td; 240 struct proc *p; 241 struct kse *ke; 242 struct ksegrp *kg; 243 int realstathz; 244 int awake; 245 246 realstathz = stathz ? stathz : hz; 247 sx_slock(&allproc_lock); 248 FOREACH_PROC_IN_SYSTEM(p) { 249 mtx_lock_spin(&sched_lock); 250 p->p_swtime++; 251 FOREACH_KSEGRP_IN_PROC(p, kg) { 252 awake = 0; 253 FOREACH_KSE_IN_GROUP(kg, ke) { 254 /* 255 * Increment time in/out of memory and sleep 256 * time (if sleeping). We ignore overflow; 257 * with 16-bit int's (remember them?) 258 * overflow takes 45 days. 259 */ 260 /* 261 * The kse slptimes are not touched in wakeup 262 * because the thread may not HAVE a KSE. 263 */ 264 if (ke->ke_state == KES_ONRUNQ) { 265 awake = 1; 266 ke->ke_flags &= ~KEF_DIDRUN; 267 } else if ((ke->ke_state == KES_THREAD) && 268 (TD_IS_RUNNING(ke->ke_thread))) { 269 awake = 1; 270 /* Do not clear KEF_DIDRUN */ 271 } else if (ke->ke_flags & KEF_DIDRUN) { 272 awake = 1; 273 ke->ke_flags &= ~KEF_DIDRUN; 274 } 275 276 /* 277 * pctcpu is only for ps? 278 * Do it per kse.. and add them up at the end? 279 * XXXKSE 280 */ 281 ke->ke_pctcpu 282 = (ke->ke_pctcpu * ccpu) >> FSHIFT; 283 /* 284 * If the kse has been idle the entire second, 285 * stop recalculating its priority until 286 * it wakes up. 287 */ 288 if (ke->ke_cpticks == 0) 289 continue; 290#if (FSHIFT >= CCPU_SHIFT) 291 ke->ke_pctcpu += (realstathz == 100) ? 292 ((fixpt_t) ke->ke_cpticks) << 293 (FSHIFT - CCPU_SHIFT) : 294 100 * (((fixpt_t) ke->ke_cpticks) << 295 (FSHIFT - CCPU_SHIFT)) / realstathz; 296#else 297 ke->ke_pctcpu += ((FSCALE - ccpu) * 298 (ke->ke_cpticks * FSCALE / realstathz)) >> 299 FSHIFT; 300#endif 301 ke->ke_cpticks = 0; 302 } /* end of kse loop */ 303 /* 304 * If there are ANY running threads in this KSEGRP, 305 * then don't count it as sleeping. 306 */ 307 if (awake) { 308 if (kg->kg_slptime > 1) { 309 /* 310 * In an ideal world, this should not 311 * happen, because whoever woke us 312 * up from the long sleep should have 313 * unwound the slptime and reset our 314 * priority before we run at the stale 315 * priority. Should KASSERT at some 316 * point when all the cases are fixed. 317 */ 318 updatepri(kg); 319 } 320 kg->kg_slptime = 0; 321 } else { 322 kg->kg_slptime++; 323 } 324 if (kg->kg_slptime > 1) 325 continue; 326 kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu); 327 resetpriority(kg); 328 FOREACH_THREAD_IN_GROUP(kg, td) { 329 if (td->td_priority >= PUSER) { 330 sched_prio(td, kg->kg_user_pri); 331 } 332 } 333 } /* end of ksegrp loop */ 334 mtx_unlock_spin(&sched_lock); 335 } /* end of process loop */ 336 sx_sunlock(&allproc_lock); 337 callout_reset(&schedcpu_callout, hz, schedcpu, NULL); 338} 339 340/* 341 * Recalculate the priority of a process after it has slept for a while. 342 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at 343 * least six times the loadfactor will decay p_estcpu to zero. 344 */ 345static void 346updatepri(struct ksegrp *kg) 347{ 348 register unsigned int newcpu; 349 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 350 351 newcpu = kg->kg_estcpu; 352 if (kg->kg_slptime > 5 * loadfac) 353 kg->kg_estcpu = 0; 354 else { 355 kg->kg_slptime--; /* the first time was done in schedcpu */ 356 while (newcpu && --kg->kg_slptime) 357 newcpu = decay_cpu(loadfac, newcpu); 358 kg->kg_estcpu = newcpu; 359 } 360 resetpriority(kg); 361} 362 363/* 364 * Compute the priority of a process when running in user mode. 365 * Arrange to reschedule if the resulting priority is better 366 * than that of the current process. 367 */ 368static void 369resetpriority(struct ksegrp *kg) 370{ 371 register unsigned int newpriority; 372 struct thread *td; 373 374 mtx_lock_spin(&sched_lock); 375 if (kg->kg_pri_class == PRI_TIMESHARE) { 376 newpriority = PUSER + kg->kg_estcpu / INVERSE_ESTCPU_WEIGHT + 377 NICE_WEIGHT * (kg->kg_nice - PRIO_MIN); 378 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE), 379 PRI_MAX_TIMESHARE); 380 kg->kg_user_pri = newpriority; 381 } 382 FOREACH_THREAD_IN_GROUP(kg, td) { 383 maybe_resched(td); /* XXXKSE silly */ 384 } 385 mtx_unlock_spin(&sched_lock); 386} 387 388/* ARGSUSED */ 389static void 390sched_setup(void *dummy) 391{ 392 if (sched_quantum == 0) 393 sched_quantum = SCHED_QUANTUM; 394 hogticks = 2 * sched_quantum; 395 396 callout_init(&schedcpu_callout, 1); 397 callout_init(&roundrobin_callout, 0); 398 399 /* Kick off timeout driven events by calling first time. */ 400 roundrobin(NULL); 401 schedcpu(NULL); 402} 403 404/* External interfaces start here */ 405int 406sched_runnable(void) 407{ 408 return runq_check(&runq); 409} 410 411int 412sched_rr_interval(void) 413{ 414 if (sched_quantum == 0) 415 sched_quantum = SCHED_QUANTUM; 416 return (sched_quantum); 417} 418 419/* 420 * We adjust the priority of the current process. The priority of 421 * a process gets worse as it accumulates CPU time. The cpu usage 422 * estimator (p_estcpu) is increased here. resetpriority() will 423 * compute a different priority each time p_estcpu increases by 424 * INVERSE_ESTCPU_WEIGHT 425 * (until MAXPRI is reached). The cpu usage estimator ramps up 426 * quite quickly when the process is running (linearly), and decays 427 * away exponentially, at a rate which is proportionally slower when 428 * the system is busy. The basic principle is that the system will 429 * 90% forget that the process used a lot of CPU time in 5 * loadav 430 * seconds. This causes the system to favor processes which haven't 431 * run much recently, and to round-robin among other processes. 432 */ 433void 434sched_clock(struct thread *td) 435{ 436 struct kse *ke; 437 struct ksegrp *kg; 438 439 KASSERT((td != NULL), ("schedclock: null thread pointer")); 440 ke = td->td_kse; 441 kg = td->td_ksegrp; 442 ke->ke_cpticks++; 443 kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1); 444 if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { 445 resetpriority(kg); 446 if (td->td_priority >= PUSER) 447 td->td_priority = kg->kg_user_pri; 448 } 449} 450/* 451 * charge childs scheduling cpu usage to parent. 452 * 453 * XXXKSE assume only one thread & kse & ksegrp keep estcpu in each ksegrp. 454 * Charge it to the ksegrp that did the wait since process estcpu is sum of 455 * all ksegrps, this is strictly as expected. Assume that the child process 456 * aggregated all the estcpu into the 'built-in' ksegrp. 457 */ 458void 459sched_exit(struct ksegrp *kg, struct ksegrp *child) 460{ 461 kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + child->kg_estcpu); 462} 463 464void 465sched_fork(struct ksegrp *kg, struct ksegrp *child) 466{ 467 /* 468 * set priority of child to be that of parent. 469 * XXXKSE this needs redefining.. 470 */ 471 child->kg_estcpu = kg->kg_estcpu; 472} 473 474void 475sched_nice(struct ksegrp *kg, int nice) 476{ 477 kg->kg_nice = nice; 478 resetpriority(kg); 479} 480 481/* 482 * Adjust the priority of a thread. 483 * This may include moving the thread within the KSEGRP, 484 * changing the assignment of a kse to the thread, 485 * and moving a KSE in the system run queue. 486 */ 487void 488sched_prio(struct thread *td, u_char prio) 489{ 490 491 if (TD_ON_RUNQ(td)) { 492 adjustrunqueue(td, prio); 493 } else { 494 td->td_priority = prio; 495 } 496} 497 498void 499sched_sleep(struct thread *td, u_char prio) 500{ 501 td->td_ksegrp->kg_slptime = 0; 502 td->td_priority = prio; 503} 504 505void 506sched_switchin(struct thread *td) 507{ 508 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 509} 510 511void 512sched_switchout(struct thread *td) 513{ 514 struct kse *ke; 515 struct proc *p; 516 517 ke = td->td_kse; 518 p = td->td_proc; 519 520 KASSERT((ke->ke_state == KES_THREAD), ("mi_switch: kse state?")); 521 522 td->td_lastcpu = ke->ke_oncpu; 523 td->td_last_kse = ke; 524 ke->ke_oncpu = NOCPU; 525 ke->ke_flags &= ~KEF_NEEDRESCHED; 526 /* 527 * At the last moment, if this thread is still marked RUNNING, 528 * then put it back on the run queue as it has not been suspended 529 * or stopped or any thing else similar. 530 */ 531 if (TD_IS_RUNNING(td)) { 532 /* Put us back on the run queue (kse and all). */ 533 setrunqueue(td); 534 } else if (p->p_flag & P_KSES) { 535 /* 536 * We will not be on the run queue. So we must be 537 * sleeping or similar. As it's available, 538 * someone else can use the KSE if they need it. 539 * (If bound LOANING can still occur). 540 */ 541 kse_reassign(ke); 542 } 543} 544 545void 546sched_wakeup(struct thread *td) 547{ 548 struct ksegrp *kg; 549 550 kg = td->td_ksegrp; 551 if (kg->kg_slptime > 1) 552 updatepri(kg); 553 kg->kg_slptime = 0; 554 setrunqueue(td); 555 maybe_resched(td); 556} 557 558void 559sched_add(struct kse *ke) 560{ 561 mtx_assert(&sched_lock, MA_OWNED); 562 KASSERT((ke->ke_thread != NULL), ("runq_add: No thread on KSE")); 563 KASSERT((ke->ke_thread->td_kse != NULL), 564 ("runq_add: No KSE on thread")); 565 KASSERT(ke->ke_state != KES_ONRUNQ, 566 ("runq_add: kse %p (%s) already in run queue", ke, 567 ke->ke_proc->p_comm)); 568 KASSERT(ke->ke_proc->p_sflag & PS_INMEM, 569 ("runq_add: process swapped out")); 570 ke->ke_ksegrp->kg_runq_kses++; 571 ke->ke_state = KES_ONRUNQ; 572 573 runq_add(&runq, ke); 574} 575 576void 577sched_rem(struct kse *ke) 578{ 579 KASSERT(ke->ke_proc->p_sflag & PS_INMEM, 580 ("runq_remove: process swapped out")); 581 KASSERT((ke->ke_state == KES_ONRUNQ), ("KSE not on run queue")); 582 mtx_assert(&sched_lock, MA_OWNED); 583 584 runq_remove(&runq, ke); 585 ke->ke_state = KES_THREAD; 586 ke->ke_ksegrp->kg_runq_kses--; 587} 588 589struct kse * 590sched_choose(void) 591{ 592 struct kse *ke; 593 594 ke = runq_choose(&runq); 595 596 if (ke != NULL) { 597 runq_remove(&runq, ke); 598 ke->ke_state = KES_THREAD; 599 600 KASSERT((ke->ke_thread != NULL), 601 ("runq_choose: No thread on KSE")); 602 KASSERT((ke->ke_thread->td_kse != NULL), 603 ("runq_choose: No KSE on thread")); 604 KASSERT(ke->ke_proc->p_sflag & PS_INMEM, 605 ("runq_choose: process swapped out")); 606 } 607 return (ke); 608} 609 610void 611sched_userret(struct thread *td) 612{ 613 struct ksegrp *kg; 614 /* 615 * XXX we cheat slightly on the locking here to avoid locking in 616 * the usual case. Setting td_priority here is essentially an 617 * incomplete workaround for not setting it properly elsewhere. 618 * Now that some interrupt handlers are threads, not setting it 619 * properly elsewhere can clobber it in the window between setting 620 * it here and returning to user mode, so don't waste time setting 621 * it perfectly here. 622 */ 623 kg = td->td_ksegrp; 624 if (td->td_priority != kg->kg_user_pri) { 625 mtx_lock_spin(&sched_lock); 626 td->td_priority = kg->kg_user_pri; 627 mtx_unlock_spin(&sched_lock); 628 } 629} 630 631int 632sched_sizeof_kse(void) 633{ 634 return (sizeof(struct kse)); 635} 636int 637sched_sizeof_ksegrp(void) 638{ 639 return (sizeof(struct ksegrp)); 640} 641int 642sched_sizeof_proc(void) 643{ 644 return (sizeof(struct proc)); 645} 646int 647sched_sizeof_thread(void) 648{ 649 return (sizeof(struct thread)); 650} 651