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ev_select.c

/*
 * FD polling functions for generic select()
 *
 * Copyright 2000-2007 Willy Tarreau <w@1wt.eu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 */

#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>

#include <common/compat.h>
#include <common/config.h>
#include <common/time.h>

#include <types/fd.h>
#include <types/global.h>

#include <proto/fd.h>
#include <proto/task.h>


static fd_set *fd_evts[2];
static fd_set *tmp_evts[2];


/*
 * Benchmarks performed on a Pentium-M notebook show that using functions
 * instead of the usual macros improve the FD_* performance by about 80%,
 * and that marking them regparm(2) adds another 20%.
 */
REGPRM2 static int __fd_is_set(const int fd, int dir)
{
      return FD_ISSET(fd, fd_evts[dir]);
}

REGPRM2 static int __fd_set(const int fd, int dir)
{
      FD_SET(fd, fd_evts[dir]);
      return 0;
}

REGPRM2 static int __fd_clr(const int fd, int dir)
{
      FD_CLR(fd, fd_evts[dir]);
      return 0;
}

REGPRM2 static int __fd_cond_s(const int fd, int dir)
{
      int ret;
      ret = !FD_ISSET(fd, fd_evts[dir]);
      if (ret)
            FD_SET(fd, fd_evts[dir]);
      return ret;
}

REGPRM2 static int __fd_cond_c(const int fd, int dir)
{
      int ret;
      ret = FD_ISSET(fd, fd_evts[dir]);
      if (ret)
            FD_CLR(fd, fd_evts[dir]);
      return ret;
}

REGPRM1 static void __fd_rem(int fd)
{
      FD_CLR(fd, fd_evts[DIR_RD]);
      FD_CLR(fd, fd_evts[DIR_WR]);
}

/*
 * Select() poller
 */
REGPRM2 static void _do_poll(struct poller *p, struct timeval *exp)
{
      int status;
      int fd, i;
      struct timeval delta;
      int readnotnull, writenotnull;
      int fds;
      char count;
            
      /* allow select to return immediately when needed */
      delta.tv_sec = delta.tv_usec = 0;
      if (tv_isset(exp)) {
            if (tv_islt(&now, exp)) {
                  tv_remain(&now, exp, &delta);
                  /* To avoid eventual select loops due to timer precision */
                  delta.tv_usec += SCHEDULER_RESOLUTION * 1000;
                  if (delta.tv_usec >= 1000000) {
                        delta.tv_usec -= 1000000;
                        delta.tv_sec ++;
                  }
            }
      }

      /* let's restore fdset state */

      readnotnull = 0; writenotnull = 0;
      for (i = 0; i < (maxfd + FD_SETSIZE - 1)/(8*sizeof(int)); i++) {
            readnotnull |= (*(((int*)tmp_evts[DIR_RD])+i) = *(((int*)fd_evts[DIR_RD])+i)) != 0;
            writenotnull |= (*(((int*)tmp_evts[DIR_WR])+i) = *(((int*)fd_evts[DIR_WR])+i)) != 0;
      }

      //    /* just a verification code, needs to be removed for performance */
      //    for (i=0; i<maxfd; i++) {
      //        if (FD_ISSET(i, tmp_evts[DIR_RD]) != FD_ISSET(i, fd_evts[DIR_RD]))
      //          abort();
      //        if (FD_ISSET(i, tmp_evts[DIR_WR]) != FD_ISSET(i, fd_evts[DIR_WR]))
      //          abort();
      //        
      //    }

      status = select(maxfd,
                  readnotnull ? tmp_evts[DIR_RD] : NULL,
                  writenotnull ? tmp_evts[DIR_WR] : NULL,
                  NULL,
                  tv_isset(exp) ? &delta : NULL);
      
      tv_now(&now);

      if (status <= 0)
            return;

      for (fds = 0; (fds << INTBITS) < maxfd; fds++) {
            if ((((int *)(tmp_evts[DIR_RD]))[fds] | ((int *)(tmp_evts[DIR_WR]))[fds]) == 0)
                  continue;

            for (count = 1<<INTBITS, fd = fds << INTBITS; count && fd < maxfd; count--, fd++) {
                  /* if we specify read first, the accepts and zero reads will be
                   * seen first. Moreover, system buffers will be flushed faster.
                   */
                  if (FD_ISSET(fd, tmp_evts[DIR_RD])) {
                        if (fdtab[fd].state == FD_STCLOSE)
                              continue;
                        fdtab[fd].cb[DIR_RD].f(fd);
                  }

                  if (FD_ISSET(fd, tmp_evts[DIR_WR])) {
                        if (fdtab[fd].state == FD_STCLOSE)
                              continue;
                        fdtab[fd].cb[DIR_WR].f(fd);
                  }
            }
      }
}

/*
 * Initialization of the select() poller.
 * Returns 0 in case of failure, non-zero in case of success. If it fails, it
 * disables the poller by setting its pref to 0.
 */
REGPRM1 static int _do_init(struct poller *p)
{
      __label__ fail_swevt, fail_srevt, fail_wevt, fail_revt;
      int fd_set_bytes;

      p->private = NULL;
      fd_set_bytes = sizeof(fd_set) * (global.maxsock + FD_SETSIZE - 1) / FD_SETSIZE;

      if ((tmp_evts[DIR_RD] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
            goto fail_revt;
            
      if ((tmp_evts[DIR_WR] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
            goto fail_wevt;

      if ((fd_evts[DIR_RD] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
            goto fail_srevt;

      if ((fd_evts[DIR_WR] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
            goto fail_swevt;

      return 1;

 fail_swevt:
      free(fd_evts[DIR_RD]);
 fail_srevt:
      free(tmp_evts[DIR_WR]);
 fail_wevt:
      free(tmp_evts[DIR_RD]);
 fail_revt:
      p->pref = 0;
      return 0;
}

/*
 * Termination of the select() poller.
 * Memory is released and the poller is marked as unselectable.
 */
REGPRM1 static void _do_term(struct poller *p)
{
      if (fd_evts[DIR_WR])
            free(fd_evts[DIR_WR]);
      if (fd_evts[DIR_RD])
            free(fd_evts[DIR_RD]);
      if (tmp_evts[DIR_WR])
            free(tmp_evts[DIR_WR]);
      if (tmp_evts[DIR_RD])
            free(tmp_evts[DIR_RD]);
      p->private = NULL;
      p->pref = 0;
}

/*
 * Check that the poller works.
 * Returns 1 if OK, otherwise 0.
 */
REGPRM1 static int _do_test(struct poller *p)
{
      return 1;
}

/*
 * It is a constructor, which means that it will automatically be called before
 * main(). This is GCC-specific but it works at least since 2.95.
 * Special care must be taken so that it does not need any uninitialized data.
 */
__attribute__((constructor))
static void _do_register(void)
{
      struct poller *p;

      if (nbpollers >= MAX_POLLERS)
            return;
      p = &pollers[nbpollers++];

      p->name = "select";
      p->pref = 150;
      p->private = NULL;

      p->test = _do_test;
      p->init = _do_init;
      p->term = _do_term;
      p->poll = _do_poll;
      p->is_set = __fd_is_set;
      p->set = __fd_set;
      p->clr = __fd_clr;
      p->clo = p->rem = __fd_rem;
      p->cond_s = __fd_cond_s;
      p->cond_c = __fd_cond_c;
}


/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */

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