Date: Mon, 17 Feb 1997 01:37:35 +0300 (MSK) From: =?KOI8-R?B?4c7E0sXKIP7F0s7P1w==?= <ache@nagual.ru> To: Bruce Evans <bde@zeta.org.au> Cc: peter@spinner.dialix.com, cvs-all@freefall.freebsd.org, CVS-committers@freefall.freebsd.org, cvs-sys@freefall.freebsd.org, mpp@freefall.freebsd.org Subject: Re: cvs commit: src/sys/sys types.h Message-ID: <Pine.BSF.3.95q.970217013428.575B-100000@nagual.ru> In-Reply-To: <199702161404.BAA20251@godzilla.zeta.org.au>
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On Mon, 17 Feb 1997, Bruce Evans wrote:
> >+ #define FD_ROUNDSIZE 256
> >+
>
> Change to something like (2048 / 6) = 341. Now that's an odd size :-).
I change it (see update patch below) but still not understand
why 2048 is here. p_selbits_size increasing constant will be 44 in this
case, is it good value for you too?
> Don't use this except possibly for very large ni together with unusual
> combinations of fds. Put 3 contiguous copyout buffers first (readfds,
> writefds, exexptfds), then 3 copyin buffers, and bzero 1*ni, 2*ni or
> 3*ni bits as necessary (exceptfds is usually NULL so the bzero doesn't
> need to cover it). The old code got this wrong mainly by spacing the
> buffers with separation p->p_selbits_size instead of ni.
I try to implement what you say, see the patch below:
*** sys_generic.c.orig Tue Jan 14 23:11:28 1997
--- sys_generic.c Mon Feb 17 01:33:11 1997
***************
*** 508,513 ****
--- 508,515 ----
return (error);
}
+ #define FD_ROUNDSIZE (2048 / (3 + 3))
+
static int nselcoll;
int selwait;
***************
*** 539,545 ****
uap->nd = p->p_fd->fd_nfiles; /* forgiving; slightly wrong */
/* The amount of space we need to allocate */
! ni = howmany(roundup2 (uap->nd, FD_SETSIZE), NFDBITS) *
sizeof(fd_mask);
if (ni > p->p_selbits_size) {
--- 541,547 ----
uap->nd = p->p_fd->fd_nfiles; /* forgiving; slightly wrong */
/* The amount of space we need to allocate */
! ni = howmany(roundup2 (uap->nd, FD_ROUNDSIZE), NFDBITS) *
sizeof(fd_mask);
if (ni > p->p_selbits_size) {
***************
*** 547,571 ****
free (p->p_selbits, M_SELECT);
while (p->p_selbits_size < ni)
! p->p_selbits_size += 32; /* Increase by 256 bits */
p->p_selbits = malloc(p->p_selbits_size * 6, M_SELECT,
M_WAITOK);
}
- for (i = 0; i < 3; i++) {
- ibits[i] = (fd_mask *)(p->p_selbits + i * p->p_selbits_size);
- obits[i] = (fd_mask *)(p->p_selbits + (i + 3) *
- p->p_selbits_size);
- }
-
- /*
- * This buffer is usually very small therefore it's probably faster
- * to just zero it, rather than calculate what needs to be zeroed.
- */
- bzero (p->p_selbits, p->p_selbits_size * 6);
/* The amount of space we need to copyin/copyout */
ni = howmany(uap->nd, NFDBITS) * sizeof(fd_mask);
#define getbits(name, x) \
if (uap->name && \
--- 549,579 ----
free (p->p_selbits, M_SELECT);
while (p->p_selbits_size < ni)
! p->p_selbits_size +=
! howmany(FD_ROUNDSIZE, NFDBITS) *
! sizeof(fd_mask);
p->p_selbits = malloc(p->p_selbits_size * 6, M_SELECT,
M_WAITOK);
}
/* The amount of space we need to copyin/copyout */
ni = howmany(uap->nd, NFDBITS) * sizeof(fd_mask);
+
+ for (i = 0; i < 3; i++) {
+ obits[i] = (fd_mask *)(p->p_selbits + i * ni);
+ ibits[i] = (fd_mask *)(p->p_selbits + (i + 3) * ni);
+ }
+ if (uap->ex)
+ i = 3;
+ else if (uap->ou)
+ i = 2;
+ else if (uap->in)
+ i = 1;
+ else
+ i = 0;
+ if (i)
+ bzero(p->p_selbits, i * ni);
#define getbits(name, x) \
if (uap->name && \
--
Andrey A. Chernov
<ache@null.net>
http://www.nagual.ru/~ache/
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