Re: performance experiment

[David Mosberger]

>>>>> On Fri, 26 Jul 2002 13:49:27 -0700 (PDT), Davide Libenzi <[e-mail]> said:

  Davide> IMHO the patch makes sense, it reduces memory loads and it
  Davide> "helps" the compiler to correctly allocate registers.

I just realized that a gcc3 feature snuck into the source-code by
accident.  Below is a fixed patch which should work with gcc2 as well.

	--david

--- linux-2.4.18/fs/select.c	Mon Sep 24 15:08:21 2001
+++ lia64-2.4/fs/select.c	Fri Jul 26 18:26:38 2002
@@ -164,7 +164,7 @@
 int do_select(int n, fd_set_bits *fds, long *timeout)
 {
 	poll_table table, *wait;
-	int retval, i, off;
+	long retval, i, off;
 	long __timeout = *timeout;
 
  	read_lock(&current->files->file_lock);
@@ -181,6 +181,7 @@
 		wait = NULL;
 	retval = 0;
 	for (;;) {
+#if 0
 		set_current_state(TASK_INTERRUPTIBLE);
 		for (i = 0 ; i < n; i++) {
 			unsigned long bit = BIT(i);
@@ -214,6 +215,57 @@
 				wait = NULL;
 			}
 		}
+#else
+		unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
+
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		inp = fds->in; outp = fds->out; exp = fds->ex;
+		rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
+
+		for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
+			unsigned long in, out, ex, all_bits, bit = 1, mask, j;
+			unsigned long res_in = 0, res_out = 0, res_ex = 0;
+			struct file_operations *f_op;
+			struct file *file = NULL;
+
+			in = *inp++; out = *outp++; ex = *exp++;
+			all_bits = in | out | ex;
+			if (all_bits == 0)
+				continue;
+
+			for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
+				if (i >= n)
+					break;
+				if (!(bit & all_bits))
+					continue;
+				file = fget(i);
+				if (file)
+					f_op = file->f_op;
+				mask = DEFAULT_POLLMASK;
+				if (file) {
+					if (f_op && f_op->poll)
+						mask = (*f_op->poll)(file, retval ? NULL : wait);
+					fput(file);
+					if ((mask & POLLIN_SET) && (in & bit)) {
+						res_in |= bit;
+						retval++;
+					}
+					if ((mask & POLLOUT_SET) && (out & bit)) {
+						res_out |= bit;
+						retval++;
+					}
+					if ((mask & POLLEX_SET) && (ex & bit)) {
+						res_ex |= bit;
+						retval++;
+					}
+				}
+			}
+			if (res_in) *rinp = res_in;
+			if (res_out) *routp = res_out;
+			if (res_ex) *rexp = res_ex;
+		}
+#endif
 		wait = NULL;
 		if (retval || !__timeout || signal_pending(current))
 			break;