CLEANUP: fdtab: flatten the struct and merge the spec struct with the rest

The "spec" sub-struct was using 8 bytes for only 5 needed. There is no
reason to keep it as a struct, it doesn't bring any value. By flattening
it, we can merge the single byte with the next single byte, resulting in
an immediate saving of 4 bytes (20%). Interestingly, tests have shown a
steady performance gain of 0.6% after this change, which can possibly be
attributed to a more cache-line friendly struct.

diff --git a/include/types/fd.h b/include/types/fd.h
index f45b04603f3d1a875c83baf28dbf59dbe8b7a55c..1ccb0ebede9c132e5919ce741008e5bd3d924be9 100644 (file)
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -55,10 +55,8 @@ enum {
 struct fdtab {
        int (*iocb)(int fd);                 /* I/O handler, returns FD_WAIT_* */
        void *owner;                         /* the connection or listener associated with this fd, NULL if closed */
-       struct {                             /* used by pollers which support speculative polling */
-               unsigned char e;             /* read and write events status. 4 bits, may be merged into flags' lower bits */
-               unsigned int s1;             /* Position in spec list+1. 0=not in list. */
-       } spec;
+       unsigned int  spec_p;                /* speculative polling: position in spec list+1. 0=not in list. */
+       unsigned char spec_e;                /* speculative polling: read and write events status. 4 bits */
        unsigned char ev;                    /* event seen in return of poll() : FD_POLL_* */
 };
 

diff --git a/src/ev_sepoll.c b/src/ev_sepoll.c
index 7c1cf4c535708931344875ef88060f84509dd177..bb2e47e37d3d726e612416e928bf655518d2c661 100644 (file)
--- a/src/ev_sepoll.c
+++ b/src/ev_sepoll.c
@@ -105,7 +105,7 @@
  * The FD array has to hold a back reference to the speculative list. This
  * reference is only valid if at least one of the directions is marked SPEC.
  *
- * We store the FD state in the 4 lower bits of fdtab[fd].spec.e, and save the
+ * We store the FD state in the 4 lower bits of fdtab[fd].spec_e, and save the
  * previous state upon changes in the 4 higher bits, so that changes are easy
  * to spot.
  */
@@ -160,10 +160,10 @@ static struct epoll_event ev;
 
 REGPRM1 static inline void alloc_spec_entry(const int fd)
 {
-       if (fdtab[fd].spec.s1)
+       if (fdtab[fd].spec_p)
                /* sometimes the entry already exists for the other direction */
                return;
-       fdtab[fd].spec.s1 = nbspec + 1;
+       fdtab[fd].spec_p = nbspec + 1;
        spec_list[nbspec] = fd;
        nbspec++;
 }
@@ -176,11 +176,11 @@ REGPRM1 static void release_spec_entry(int fd)
 {
        unsigned int pos;
 
-       pos = fdtab[fd].spec.s1;
+       pos = fdtab[fd].spec_p;
        if (!pos)
                return;
 
-       fdtab[fd].spec.s1 = 0;
+       fdtab[fd].spec_p = 0;
        pos--;
        /* we have spec_list[pos]==fd */
 
@@ -191,7 +191,7 @@ REGPRM1 static void release_spec_entry(int fd)
        /* we replace current FD by the highest one, which may sometimes be the same */
        fd = spec_list[nbspec];
        spec_list[pos] = fd;
-       fdtab[fd].spec.s1 = pos + 1;
+       fdtab[fd].spec_p = pos + 1;
 }
 
 /*
@@ -207,7 +207,7 @@ REGPRM2 static int __fd_is_set(const int fd, int dir)
                ABORT_NOW();
        }
 #endif
-       ret = ((unsigned)fdtab[fd].spec.e >> dir) & FD_EV_MASK_DIR;
+       ret = ((unsigned)fdtab[fd].spec_e >> dir) & FD_EV_MASK_DIR;
        return (ret == FD_EV_SPEC || ret == FD_EV_WAIT);
 }
 
@@ -225,14 +225,14 @@ REGPRM2 static void __fd_wai(const int fd, int dir)
                ABORT_NOW();
        }
 #endif
-       i = ((unsigned)fdtab[fd].spec.e >> dir) & FD_EV_MASK_DIR;
+       i = ((unsigned)fdtab[fd].spec_e >> dir) & FD_EV_MASK_DIR;
 
        if (!(i & FD_EV_IN_SL)) {
                if (i == FD_EV_WAIT)
                        return; /* already in desired state */
                alloc_spec_entry(fd); /* need a spec entry */
        }
-       fdtab[fd].spec.e ^= (i ^ (unsigned int)FD_EV_IN_PL) << dir;
+       fdtab[fd].spec_e ^= (i ^ (unsigned int)FD_EV_IN_PL) << dir;
 }
 
 REGPRM2 static void __fd_set(const int fd, int dir)
@@ -245,7 +245,7 @@ REGPRM2 static void __fd_set(const int fd, int dir)
                ABORT_NOW();
        }
 #endif
-       i = ((unsigned)fdtab[fd].spec.e >> dir) & FD_EV_MASK_DIR;
+       i = ((unsigned)fdtab[fd].spec_e >> dir) & FD_EV_MASK_DIR;
 
        if (i != FD_EV_STOP) {
                if (unlikely(i != FD_EV_IDLE))
@@ -253,7 +253,7 @@ REGPRM2 static void __fd_set(const int fd, int dir)
                // switch to SPEC state and allocate a SPEC entry.
                alloc_spec_entry(fd);
        }
-       fdtab[fd].spec.e ^= (unsigned int)(FD_EV_IN_SL << dir);
+       fdtab[fd].spec_e ^= (unsigned int)(FD_EV_IN_SL << dir);
 }
 
 REGPRM2 static void __fd_clr(const int fd, int dir)
@@ -266,7 +266,7 @@ REGPRM2 static void __fd_clr(const int fd, int dir)
                ABORT_NOW();
        }
 #endif
-       i = ((unsigned)fdtab[fd].spec.e >> dir) & FD_EV_MASK_DIR;
+       i = ((unsigned)fdtab[fd].spec_e >> dir) & FD_EV_MASK_DIR;
 
        if (i != FD_EV_SPEC) {
                if (unlikely(i != FD_EV_WAIT))
@@ -278,7 +278,7 @@ REGPRM2 static void __fd_clr(const int fd, int dir)
                 */
                alloc_spec_entry(fd);
        }
-       fdtab[fd].spec.e ^= (unsigned int)(FD_EV_IN_SL << dir);
+       fdtab[fd].spec_e ^= (unsigned int)(FD_EV_IN_SL << dir);
 }
 
 /* normally unused */
@@ -295,7 +295,7 @@ REGPRM1 static void __fd_rem(int fd)
 REGPRM1 static void __fd_clo(int fd)
 {
        release_spec_entry(fd);
-       fdtab[fd].spec.e &= ~(FD_EV_MASK | FD_EV_MASK_OLD);
+       fdtab[fd].spec_e &= ~(FD_EV_MASK | FD_EV_MASK_OLD);
 }
 
 /*
@@ -314,8 +314,8 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
        while (likely(spec_idx > 0)) {
                spec_idx--;
                fd = spec_list[spec_idx];
-               en = fdtab[fd].spec.e & 15;  /* new events */
-               eo = fdtab[fd].spec.e >> 4;  /* previous events */
+               en = fdtab[fd].spec_e & 15;  /* new events */
+               eo = fdtab[fd].spec_e >> 4;  /* previous events */
 
                /* If an fd with a poll bit is present here, it means that it
                 * has last requested a poll, or is leaving from a poll. Given
@@ -372,9 +372,9 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
                        epoll_ctl(epoll_fd, opcode, fd, &ev);
                }
 
-               fdtab[fd].spec.e = (en << 4) + en;  /* save new events */
+               fdtab[fd].spec_e = (en << 4) + en;  /* save new events */
 
-               if (!(fdtab[fd].spec.e & FD_EV_RW_SL)) {
+               if (!(fdtab[fd].spec_e & FD_EV_RW_SL)) {
                        /* This fd switched to combinations of either WAIT or
                         * IDLE. It must be removed from the spec list.
                         */
@@ -447,7 +447,7 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
        while (likely(spec_idx > 0)) {
                spec_idx--;
                fd = spec_list[spec_idx];
-               eo = fdtab[fd].spec.e;  /* save old events */
+               eo = fdtab[fd].spec_e;  /* save old events */
 
                /*
                 * Process the speculative events.
@@ -473,7 +473,7 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
                if (!fdtab[fd].owner)
                        continue;
 
-               if (!(fdtab[fd].spec.e & (FD_EV_RW_SL|FD_EV_RW_PL))) {
+               if (!(fdtab[fd].spec_e & (FD_EV_RW_SL|FD_EV_RW_PL))) {
                        /* This fd switched to IDLE, it can be removed from the spec list. */
                        release_spec_entry(fd);
                        continue;