The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_prof.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      @(#)subr_prof.c 8.3 (Berkeley) 9/23/93
   34  * $FreeBSD$
   35  */
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/sysproto.h>
   40 #include <sys/kernel.h>
   41 #include <sys/proc.h>
   42 #include <sys/resourcevar.h>
   43 #include <sys/sysctl.h>
   44 
   45 #include <machine/ipl.h>
   46 #include <machine/cpu.h>
   47 
   48 #ifdef GPROF
   49 #include <sys/malloc.h>
   50 #include <sys/gmon.h>
   51 #undef MCOUNT
   52 
   53 static MALLOC_DEFINE(M_GPROF, "gprof", "kernel profiling buffer");
   54 
   55 static void kmstartup __P((void *));
   56 SYSINIT(kmem, SI_SUB_KPROF, SI_ORDER_FIRST, kmstartup, NULL)
   57 
   58 struct gmonparam _gmonparam = { GMON_PROF_OFF };
   59 
   60 #ifdef GUPROF
   61 #include <machine/asmacros.h>
   62 
   63 void
   64 nullfunc_loop_profiled()
   65 {
   66         int i;
   67 
   68         for (i = 0; i < CALIB_SCALE; i++)
   69                 nullfunc_profiled();
   70 }
   71 
   72 #define nullfunc_loop_profiled_end      nullfunc_profiled       /* XXX */
   73 
   74 void
   75 nullfunc_profiled()
   76 {
   77 }
   78 #endif /* GUPROF */
   79 
   80 static void
   81 kmstartup(dummy)
   82         void *dummy;
   83 {
   84         char *cp;
   85         struct gmonparam *p = &_gmonparam;
   86 #ifdef GUPROF
   87         int cputime_overhead;
   88         int empty_loop_time;
   89         int i;
   90         int mcount_overhead;
   91         int mexitcount_overhead;
   92         int nullfunc_loop_overhead;
   93         int nullfunc_loop_profiled_time;
   94         uintfptr_t tmp_addr;
   95 #endif
   96 
   97         /*
   98          * Round lowpc and highpc to multiples of the density we're using
   99          * so the rest of the scaling (here and in gprof) stays in ints.
  100          */
  101         p->lowpc = ROUNDDOWN((u_long)btext, HISTFRACTION * sizeof(HISTCOUNTER));
  102         p->highpc = ROUNDUP((u_long)etext, HISTFRACTION * sizeof(HISTCOUNTER));
  103         p->textsize = p->highpc - p->lowpc;
  104         printf("Profiling kernel, textsize=%lu [%x..%x]\n",
  105                p->textsize, p->lowpc, p->highpc);
  106         p->kcountsize = p->textsize / HISTFRACTION;
  107         p->hashfraction = HASHFRACTION;
  108         p->fromssize = p->textsize / HASHFRACTION;
  109         p->tolimit = p->textsize * ARCDENSITY / 100;
  110         if (p->tolimit < MINARCS)
  111                 p->tolimit = MINARCS;
  112         else if (p->tolimit > MAXARCS)
  113                 p->tolimit = MAXARCS;
  114         p->tossize = p->tolimit * sizeof(struct tostruct);
  115         cp = (char *)malloc(p->kcountsize + p->fromssize + p->tossize,
  116             M_GPROF, M_NOWAIT);
  117         if (cp == 0) {
  118                 printf("No memory for profiling.\n");
  119                 return;
  120         }
  121         bzero(cp, p->kcountsize + p->tossize + p->fromssize);
  122         p->tos = (struct tostruct *)cp;
  123         cp += p->tossize;
  124         p->kcount = (HISTCOUNTER *)cp;
  125         cp += p->kcountsize;
  126         p->froms = (u_short *)cp;
  127 
  128 #ifdef GUPROF
  129         /* Initialize pointers to overhead counters. */
  130         p->cputime_count = &KCOUNT(p, PC_TO_I(p, cputime));
  131         p->mcount_count = &KCOUNT(p, PC_TO_I(p, mcount));
  132         p->mexitcount_count = &KCOUNT(p, PC_TO_I(p, mexitcount));
  133 
  134         /*
  135          * Disable interrupts to avoid interference while we calibrate
  136          * things.
  137          */
  138         disable_intr();
  139 
  140         /*
  141          * Determine overheads.
  142          * XXX this needs to be repeated for each useful timer/counter.
  143          */
  144         cputime_overhead = 0;
  145         startguprof(p);
  146         for (i = 0; i < CALIB_SCALE; i++)
  147                 cputime_overhead += cputime();
  148 
  149         empty_loop();
  150         startguprof(p);
  151         empty_loop();
  152         empty_loop_time = cputime();
  153 
  154         nullfunc_loop_profiled();
  155 
  156         /*
  157          * Start profiling.  There won't be any normal function calls since
  158          * interrupts are disabled, but we will call the profiling routines
  159          * directly to determine their overheads.
  160          */
  161         p->state = GMON_PROF_HIRES;
  162 
  163         startguprof(p);
  164         nullfunc_loop_profiled();
  165 
  166         startguprof(p);
  167         for (i = 0; i < CALIB_SCALE; i++)
  168 #if defined(__i386__) && __GNUC__ >= 2
  169                 __asm("pushl %0; call __mcount; popl %%ecx"
  170                       :
  171                       : "i" (profil)
  172                       : "ax", "bx", "cx", "dx", "memory");
  173 #else
  174 #error
  175 #endif
  176         mcount_overhead = KCOUNT(p, PC_TO_I(p, profil));
  177 
  178         startguprof(p);
  179         for (i = 0; i < CALIB_SCALE; i++)
  180 #if defined(__i386__) && __GNUC__ >= 2
  181                     __asm("call " __XSTRING(HIDENAME(mexitcount)) "; 1:"
  182                           : : : "ax", "bx", "cx", "dx", "memory");
  183         __asm("movl $1b,%0" : "=rm" (tmp_addr));
  184 #else
  185 #error
  186 #endif
  187         mexitcount_overhead = KCOUNT(p, PC_TO_I(p, tmp_addr));
  188 
  189         p->state = GMON_PROF_OFF;
  190         stopguprof(p);
  191 
  192         enable_intr();
  193 
  194         nullfunc_loop_profiled_time = 0;
  195         for (tmp_addr = (uintfptr_t)nullfunc_loop_profiled;
  196              tmp_addr < (uintfptr_t)nullfunc_loop_profiled_end;
  197              tmp_addr += HISTFRACTION * sizeof(HISTCOUNTER))
  198                 nullfunc_loop_profiled_time += KCOUNT(p, PC_TO_I(p, tmp_addr));
  199 #define CALIB_DOSCALE(count)    (((count) + CALIB_SCALE / 3) / CALIB_SCALE)
  200 #define c2n(count, freq)        ((int)((count) * 1000000000LL / freq))
  201         printf("cputime %d, empty_loop %d, nullfunc_loop_profiled %d, mcount %d, mexitcount %d\n",
  202                CALIB_DOSCALE(c2n(cputime_overhead, p->profrate)),
  203                CALIB_DOSCALE(c2n(empty_loop_time, p->profrate)),
  204                CALIB_DOSCALE(c2n(nullfunc_loop_profiled_time, p->profrate)),
  205                CALIB_DOSCALE(c2n(mcount_overhead, p->profrate)),
  206                CALIB_DOSCALE(c2n(mexitcount_overhead, p->profrate)));
  207         cputime_overhead -= empty_loop_time;
  208         mcount_overhead -= empty_loop_time;
  209         mexitcount_overhead -= empty_loop_time;
  210 
  211         /*-
  212          * Profiling overheads are determined by the times between the
  213          * following events:
  214          *      MC1: mcount() is called
  215          *      MC2: cputime() (called from mcount()) latches the timer
  216          *      MC3: mcount() completes
  217          *      ME1: mexitcount() is called
  218          *      ME2: cputime() (called from mexitcount()) latches the timer
  219          *      ME3: mexitcount() completes.
  220          * The times between the events vary slightly depending on instruction
  221          * combination and cache misses, etc.  Attempt to determine the
  222          * minimum times.  These can be subtracted from the profiling times
  223          * without much risk of reducing the profiling times below what they
  224          * would be when profiling is not configured.  Abbreviate:
  225          *      ab = minimum time between MC1 and MC3
  226          *      a  = minumum time between MC1 and MC2
  227          *      b  = minimum time between MC2 and MC3
  228          *      cd = minimum time between ME1 and ME3
  229          *      c  = minimum time between ME1 and ME2
  230          *      d  = minimum time between ME2 and ME3.
  231          * These satisfy the relations:
  232          *      ab            <= mcount_overhead                (just measured)
  233          *      a + b         <= ab
  234          *              cd    <= mexitcount_overhead            (just measured)
  235          *              c + d <= cd
  236          *      a         + d <= nullfunc_loop_profiled_time    (just measured)
  237          *      a >= 0, b >= 0, c >= 0, d >= 0.
  238          * Assume that ab and cd are equal to the minimums.
  239          */
  240         p->cputime_overhead = CALIB_DOSCALE(cputime_overhead);
  241         p->mcount_overhead = CALIB_DOSCALE(mcount_overhead - cputime_overhead);
  242         p->mexitcount_overhead = CALIB_DOSCALE(mexitcount_overhead
  243                                                - cputime_overhead);
  244         nullfunc_loop_overhead = nullfunc_loop_profiled_time - empty_loop_time;
  245         p->mexitcount_post_overhead = CALIB_DOSCALE((mcount_overhead
  246                                                      - nullfunc_loop_overhead)
  247                                                     / 4);
  248         p->mexitcount_pre_overhead = p->mexitcount_overhead
  249                                      + p->cputime_overhead
  250                                      - p->mexitcount_post_overhead;
  251         p->mcount_pre_overhead = CALIB_DOSCALE(nullfunc_loop_overhead)
  252                                  - p->mexitcount_post_overhead;
  253         p->mcount_post_overhead = p->mcount_overhead
  254                                   + p->cputime_overhead
  255                                   - p->mcount_pre_overhead;
  256         printf(
  257 "Profiling overheads: mcount: %d+%d, %d+%d; mexitcount: %d+%d, %d+%d nsec\n",
  258                c2n(p->cputime_overhead, p->profrate),
  259                c2n(p->mcount_overhead, p->profrate),
  260                c2n(p->mcount_pre_overhead, p->profrate),
  261                c2n(p->mcount_post_overhead, p->profrate),
  262                c2n(p->cputime_overhead, p->profrate),
  263                c2n(p->mexitcount_overhead, p->profrate),
  264                c2n(p->mexitcount_pre_overhead, p->profrate),
  265                c2n(p->mexitcount_post_overhead, p->profrate));
  266         printf(
  267 "Profiling overheads: mcount: %d+%d, %d+%d; mexitcount: %d+%d, %d+%d cycles\n",
  268                p->cputime_overhead, p->mcount_overhead,
  269                p->mcount_pre_overhead, p->mcount_post_overhead,
  270                p->cputime_overhead, p->mexitcount_overhead,
  271                p->mexitcount_pre_overhead, p->mexitcount_post_overhead);
  272 #endif /* GUPROF */
  273 }
  274 
  275 /*
  276  * Return kernel profiling information.
  277  */
  278 static int
  279 sysctl_kern_prof(SYSCTL_HANDLER_ARGS)
  280 {
  281         int *name = (int *) arg1;
  282         u_int namelen = arg2;
  283         struct gmonparam *gp = &_gmonparam;
  284         int error;
  285         int state;
  286 
  287         /* all sysctl names at this level are terminal */
  288         if (namelen != 1)
  289                 return (ENOTDIR);               /* overloaded */
  290 
  291         switch (name[0]) {
  292         case GPROF_STATE:
  293                 state = gp->state;
  294                 error = sysctl_handle_int(oidp, &state, 0, req);
  295                 if (error)
  296                         return (error);
  297                 if (!req->newptr)
  298                         return (0);
  299                 if (state == GMON_PROF_OFF) {
  300                         gp->state = state;
  301                         stopprofclock(&proc0);
  302                         stopguprof(gp);
  303                 } else if (state == GMON_PROF_ON) {
  304                         gp->state = GMON_PROF_OFF;
  305                         stopguprof(gp);
  306                         gp->profrate = profhz;
  307                         startprofclock(&proc0);
  308                         gp->state = state;
  309 #ifdef GUPROF
  310                 } else if (state == GMON_PROF_HIRES) {
  311                         gp->state = GMON_PROF_OFF;
  312                         stopprofclock(&proc0);
  313                         startguprof(gp);
  314                         gp->state = state;
  315 #endif
  316                 } else if (state != gp->state)
  317                         return (EINVAL);
  318                 return (0);
  319         case GPROF_COUNT:
  320                 return (sysctl_handle_opaque(oidp, 
  321                         gp->kcount, gp->kcountsize, req));
  322         case GPROF_FROMS:
  323                 return (sysctl_handle_opaque(oidp, 
  324                         gp->froms, gp->fromssize, req));
  325         case GPROF_TOS:
  326                 return (sysctl_handle_opaque(oidp, 
  327                         gp->tos, gp->tossize, req));
  328         case GPROF_GMONPARAM:
  329                 return (sysctl_handle_opaque(oidp, gp, sizeof *gp, req));
  330         default:
  331                 return (EOPNOTSUPP);
  332         }
  333         /* NOTREACHED */
  334 }
  335 
  336 SYSCTL_NODE(_kern, KERN_PROF, prof, CTLFLAG_RW, sysctl_kern_prof, "");
  337 #endif /* GPROF */
  338 
  339 /*
  340  * Profiling system call.
  341  *
  342  * The scale factor is a fixed point number with 16 bits of fraction, so that
  343  * 1.0 is represented as 0x10000.  A scale factor of 0 turns off profiling.
  344  */
  345 #ifndef _SYS_SYSPROTO_H_
  346 struct profil_args {
  347         caddr_t samples;
  348         size_t  size;
  349         size_t  offset;
  350         u_int   scale;
  351 };
  352 #endif
  353 /* ARGSUSED */
  354 int
  355 profil(p, uap)
  356         struct proc *p;
  357         register struct profil_args *uap;
  358 {
  359         register struct uprof *upp;
  360         int s;
  361 
  362         if (uap->scale > (1 << 16))
  363                 return (EINVAL);
  364         if (uap->scale == 0) {
  365                 stopprofclock(p);
  366                 return (0);
  367         }
  368         upp = &p->p_stats->p_prof;
  369 
  370         /* Block profile interrupts while changing state. */
  371         s = splstatclock();
  372         upp->pr_off = uap->offset;
  373         upp->pr_scale = uap->scale;
  374         upp->pr_base = uap->samples;
  375         upp->pr_size = uap->size;
  376         startprofclock(p);
  377         splx(s);
  378 
  379         return (0);
  380 }
  381 
  382 /*
  383  * Scale is a fixed-point number with the binary point 16 bits
  384  * into the value, and is <= 1.0.  pc is at most 32 bits, so the
  385  * intermediate result is at most 48 bits.
  386  */
  387 #define PC_TO_INDEX(pc, prof) \
  388         ((int)(((u_quad_t)((pc) - (prof)->pr_off) * \
  389             (u_quad_t)((prof)->pr_scale)) >> 16) & ~1)
  390 
  391 /*
  392  * Collect user-level profiling statistics; called on a profiling tick,
  393  * when a process is running in user-mode.  This routine may be called
  394  * from an interrupt context.  We try to update the user profiling buffers
  395  * cheaply with fuswintr() and suswintr().  If that fails, we revert to
  396  * an AST that will vector us to trap() with a context in which copyin
  397  * and copyout will work.  Trap will then call addupc_task().
  398  *
  399  * Note that we may (rarely) not get around to the AST soon enough, and
  400  * lose profile ticks when the next tick overwrites this one, but in this
  401  * case the system is overloaded and the profile is probably already
  402  * inaccurate.
  403  */
  404 void
  405 addupc_intr(p, pc, ticks)
  406         register struct proc *p;
  407         register u_long pc;
  408         u_int ticks;
  409 {
  410         register struct uprof *prof;
  411         register caddr_t addr;
  412         register u_int i;
  413         register int v;
  414 
  415         if (ticks == 0)
  416                 return;
  417         prof = &p->p_stats->p_prof;
  418         if (pc < prof->pr_off ||
  419             (i = PC_TO_INDEX(pc, prof)) >= prof->pr_size)
  420                 return;                 /* out of range; ignore */
  421 
  422         addr = prof->pr_base + i;
  423         if ((v = fuswintr(addr)) == -1 || suswintr(addr, v + ticks) == -1) {
  424                 prof->pr_addr = pc;
  425                 prof->pr_ticks = ticks;
  426                 need_proftick(p);
  427         }
  428 }
  429 
  430 /*
  431  * Much like before, but we can afford to take faults here.  If the
  432  * update fails, we simply turn off profiling.
  433  */
  434 void
  435 addupc_task(p, pc, ticks)
  436         register struct proc *p;
  437         register u_long pc;
  438         u_int ticks;
  439 {
  440         register struct uprof *prof;
  441         register caddr_t addr;
  442         register u_int i;
  443         u_short v;
  444 
  445         /* Testing P_PROFIL may be unnecessary, but is certainly safe. */
  446         if ((p->p_flag & P_PROFIL) == 0 || ticks == 0)
  447                 return;
  448 
  449         prof = &p->p_stats->p_prof;
  450         if (pc < prof->pr_off ||
  451             (i = PC_TO_INDEX(pc, prof)) >= prof->pr_size)
  452                 return;
  453 
  454         addr = prof->pr_base + i;
  455         if (copyin(addr, (caddr_t)&v, sizeof(v)) == 0) {
  456                 v += ticks;
  457                 if (copyout((caddr_t)&v, addr, sizeof(v)) == 0)
  458                         return;
  459         }
  460         stopprofclock(p);
  461 }

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