[959] in testers
minor but useful fix for text caching
daemon@ATHENA.MIT.EDU (daemon@ATHENA.MIT.EDU)
Mon Jul 30 18:07:40 1990
From: don@ATHENA.MIT.EDU
Date: Mon, 30 Jul 90 18:06:54 -0400
To: testers@ATHENA.MIT.EDU
i realized on friday night that using adb to set maxtextcache to 0
causes a running 7.1 kernel to hang. the fix is easy. i've also added
a "can't happen" panic, because if maxtextcache=0 and the text cache
isn't empty, the code's consistency assumptions go out the window.
nevertheless, i find that things now run fine when i play with maxtextcache,
even if caching is quite active at the time of the modification.
i recommend that we include this fix for 7.1 if possible, because it allows
us a special-needs fallback.
i include here a context diff and the new source for vm_text.c . -don
*** /source/bsd-4.3/common/sys/sys/vm_text.c Fri Jul 27 13:00:29 1990
--- vm_text.c Mon Jul 30 17:22:35 1990
***************
*** 92,97 ****
--- 92,98 ----
if (!(xp)->x_forw && \
&(xp)->x_forw != xtail) panic("text cache- bad null link"); \
if (x_lru != (xp)) panic("freeing non-lru text"); */ \
+ if ( xcache < 0) panic("text cache underflow"); \
if (!xcache != !(xp)->x_forw) panic("text cache size 2"); \
x_lru = (xp)->x_forw; \
}
***************
*** 178,184 ****
}
xstats.free_cache++;
xccdec(xp, u.u_procp);
! CACHE_AT_TAIL(xp);
while ( xcache > maxtextcache) { /* cache overflow */
xuntext(x_lru);
}
--- 179,187 ----
}
xstats.free_cache++;
xccdec(xp, u.u_procp);
! if ( maxtextcache > 0) {
! CACHE_AT_TAIL(xp);
! }
while ( xcache > maxtextcache) { /* cache overflow */
xuntext(x_lru);
}
========================================================================
source file follows
========================================================================
/*
* 5799-CGZ (C) COPYRIGHT IBM CORPORATION 1986,1987
* LICENSED MATERIALS - PROPERTY OF IBM
* REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
*/
/* $Header: /afs/rel-eng.athena.mit.edu/project/release/current/source/bsd-4.3/common/sys/sys/RCS/vm_text.c,v 1.12 90/07/27 13:00:08 probe Exp $ */
/* $ACIS:vm_text.c 9.1$ */
/* $Source: /afs/rel-eng.athena.mit.edu/project/release/current/source/bsd-4.3/common/sys/sys/RCS/vm_text.c,v $ */
#ifndef lint
static char *rcsid = "$Header: /afs/rel-eng.athena.mit.edu/project/release/current/source/bsd-4.3/common/sys/sys/RCS/vm_text.c,v 1.12 90/07/27 13:00:08 probe Exp $";
#endif
/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
* @(#)vm_text.c 7.1 (Berkeley) 6/5/86
*/
#include "../machine/pte.h"
#ifdef ibm032
#include "../machine/mmu.h"
#endif ibm032
#include "param.h"
#include "systm.h"
#include "map.h"
#ifndef VFS
#include "dir.h"
#include "inode.h"
#endif
#include "user.h"
#include "proc.h"
#include "text.h"
#include "buf.h"
#include "seg.h"
#include "vm.h"
#include "cmap.h"
#include "uio.h"
#include "exec.h"
#ifdef VFS
#include "vfs.h"
#include "vnode.h"
#endif /* VFS */
#define X_LOCK(xp) { \
while ((xp)->x_flag & XLOCK) { \
(xp)->x_flag |= XWANT; \
sleep((caddr_t)(xp), PSWP); \
} \
(xp)->x_flag |= XLOCK; \
}
#define XUNLOCK(xp) { \
if ((xp)->x_flag & XWANT) \
wakeup((caddr_t)(xp)); \
(xp)->x_flag &= ~(XLOCK|XWANT); \
}
#define FREE_AT_HEAD(xp) { \
(xp)->x_forw = xhead; \
xhead = (xp); \
(xp)->x_back = &xhead; \
if (xtail == &xhead) \
xtail = &(xp)->x_forw; \
else \
(xp)->x_forw->x_back = &(xp)->x_forw; \
}
#define CACHE_AT_TAIL(xp) { \
if (!xcache != !x_lru) panic("text cache size 1"); \
xcache++; \
(xp)->x_back = xtail; \
*xtail = (xp); \
xtail = &(xp)->x_forw; \
/* x_forw is NULL */ \
if (!x_lru) x_lru = (struct text *)xtail; \
}
#define ALLOC(xp) { \
*((xp)->x_back) = (xp)->x_forw; \
if ((xp)->x_forw) \
(xp)->x_forw->x_back = (xp)->x_back; \
else \
xtail = (xp)->x_back; \
(xp)->x_forw = NULL; \
(xp)->x_back = NULL; \
}
/*
* Various debugging checks are commented in the following macro
*/
#define FREE_CACHE_LRU(xp,msg) { \
/* if (!x_lru) panic("text cache underflow"); \
if (!(xp)->x_forw && \
&(xp)->x_forw != xtail) panic("text cache- bad null link"); \
if (x_lru != (xp)) panic("freeing non-lru text"); */ \
if ( xcache < 0) panic("text cache underflow"); \
if (!xcache != !(xp)->x_forw) panic("text cache size 2"); \
x_lru = (xp)->x_forw; \
}
/*
* We place free text table entries on a free list.
* All text images are treated as "sticky,"
* and are placed on the free list (as an LRU cache) when unused.
* They may be reclaimed from the free list until reused.
* Files marked sticky are locked into the table, and are never freed.
* For machines with limited swap space, this may result
* in filling up swap, and thus we allow a limit
* to be placed on the number of text images to cache.
* In that case, we free least-recently-used text.
*/
struct text *xhead, **xtail; /* text table free list */
struct text *x_lru; /* least-recently-used cached text */
int xcache; /* number of "sticky" texts retained */
/*int maxtextcache = -1; /* maximum number of "sticky" texts */
int maxtextcache = 10; /* maximum number of "sticky" texts */
struct xstats xstats; /* cache statistics */
/*
* initialize text table
*/
xinit()
{
register struct text *xp;
xtail = &xhead;
x_lru = xhead = NULL;
for (xp = text; xp < textNTEXT; xp++)
FREE_AT_HEAD(xp);
/*
* Apparently, some other routines in the kernel expect that
* negative numbers, other than -1 will turn off caching.
* AFS, does, for instance -- but we don't use it.
*/
if (maxtextcache == -1 || maxtextcache > ntext)
maxtextcache = ntext;
}
/*
* relinquish use of the shared text segment
* of a process.
*/
xfree()
{
register struct text *xp;
#ifdef VFS
register struct vnode *vp;
struct vattr vattr;
#endif /* VFS */
if ((xp = u.u_procp->p_textp) == NULL)
return;
xstats.free++;
X_LOCK(xp);
#ifdef VFS
vp = xp->x_vptr;
VOP_GETATTR(vp, &vattr, u.u_cred);
if (--xp->x_count == 0 && (vattr.va_mode & VSVTX) == 0) {
#else
if (--xp->x_count == 0 && (xp->x_iptr->i_mode & ISVTX) == 0) {
#endif
if (xp->x_flag & XTRC ||
#ifdef VFS
vattr.va_nlink == 0) { /* XXX */
#else
xp->x_iptr->i_nlink == 0) { /* XXX */
#endif /* VFS */
xp->x_rssize -= vmemfree(tptopte(u.u_procp, 0),
(int)u.u_tsize);
if (xp->x_rssize != 0)
panic("xfree rssize");
while (xp->x_poip)
sleep((caddr_t)&xp->x_poip, PSWP+1);
xp->x_flag &= ~XLOCK;
xuntext(xp);
} else {
if (xp->x_flag & XWRIT) {
xstats.free_cacheswap++;
xp->x_flag |= XUNUSED;
}
xstats.free_cache++;
xccdec(xp, u.u_procp);
if ( maxtextcache > 0) {
CACHE_AT_TAIL(xp);
}
while ( xcache > maxtextcache) { /* cache overflow */
xuntext(x_lru);
}
}
} else {
xccdec(xp, u.u_procp);
xstats.free_inuse++;
}
#ifndef ibm032
xunlink(u.u_procp);
#else ibm032
xunlink(u.u_procp, 0);
#endif ibm032
XUNLOCK(xp);
u.u_procp->p_textp = NULL;
}
/*
* Attach to a shared text segment.
* If there is no shared text, just return.
* If there is, hook up to it:
* if it is not currently being used, it has to be read
* in from the vnode (vp); the written bit is set to force it
* to be written out as appropriate.
* If it is being used, but is not currently in core,
* a swap has to be done to get it back.
*/
#ifdef P0INVALID
#ifdef VFS
xalloc(vp, ep, pagi, pziv)
#else
xalloc(ip, ep, pagi, pziv)
#endif /* VFS */
#else /* P0INVALID */
#ifdef VFS
xalloc(vp, ep, pagi)
#else
xalloc(ip, ep, pagi)
#endif /* VFS */
#endif /* P0INVALID */
#ifdef VFS
register struct vnode *vp;
#else
register struct inode *ip;
#endif
struct exec *ep;
{
register struct text *xp;
register size_t ts;
if (ep->a_text == 0)
return;
xstats.alloc++;
#ifdef VFS
while ((xp = vp->v_text) != NULL) {
#else
while ((xp = ip->i_text) != NULL) {
#endif /* VFS */
if (xp->x_flag&XLOCK) {
/*
* Wait for text to be unlocked,
* then start over (may have changed state).
*/
xwait(xp);
continue;
}
X_LOCK(xp);
if (xp->x_back) {
xstats.alloc_cachehit++;
xcache--;
if (xp == x_lru){
FREE_CACHE_LRU(xp,"hit");
}
ALLOC(xp);
xp->x_flag &= ~XUNUSED;
} else
xstats.alloc_inuse++;
xp->x_count++;
u.u_procp->p_textp = xp;
xlink(u.u_procp);
#ifdef P0INVALID
settprot(RO, pziv);
#else
settprot(RO);
#endif
XUNLOCK(xp);
return;
}
xp = xhead;
if (xp == NULL) {
tablefull("text");
psignal(u.u_procp, SIGKILL);
return;
}
#ifdef VFS
if (xp->x_vptr) {
#else
if (xp->x_iptr) {
#endif /* VFS */
if (xp != x_lru) panic("bad lru text");
xstats.alloc_cacheflush++;
if (xp->x_flag & XUNUSED)
xstats.alloc_unused++;
xuntext(xp);
}
ALLOC(xp);
xp->x_flag = XLOAD|XLOCK;
if (pagi) {
#ifdef P0INVALID
if (pziv) xp->x_flag |= XPZIV;
#endif
#ifdef VFS
xp->x_flag |= XPAGV;
#else
xp->x_flag |= XPAGI;
#endif
}
ts = clrnd(btoc(ep->a_text));
xp->x_size = ts;
if (vsxalloc(xp) == NULL) {
swkill(u.u_procp, "xalloc: no swap space");
FREE_AT_HEAD(xp);
return;
}
xp->x_count = 1;
xp->x_ccount = 0;
xp->x_rssize = 0;
#ifdef VFS
xp->x_vptr = vp;
vp->v_flag |= VTEXT;
vp->v_text = xp;
VN_HOLD(vp);
#else
xp->x_iptr = ip;
ip->i_flag |= ITEXT;
ip->i_text = xp;
ip->i_count++;
#endif /* VFS */
u.u_procp->p_textp = xp;
xlink(u.u_procp);
if (pagi == 0) {
#ifdef P0INVALID
settprot(RW, 0);
#else
settprot(RW);
#endif
u.u_procp->p_flag |= SKEEP;
#ifdef VFS
(void) vn_rdwr(UIO_READ, vp,
(caddr_t)ctob(tptov(u.u_procp, 0)),
(int)ep->a_text,
(off_t)(((ep->a_magic == 0413)
#ifdef P0INVALID
|| (ep->a_magic == 0420)
#endif P0INVALID
)?
CLBYTES:
sizeof (struct exec)),
UIO_USERSPACE, IO_UNIT, (int *)0);
#else
(void) rdwri(UIO_READ, ip,
(caddr_t)ctob(tptov(u.u_procp, 0)),
#ifdef VICE
(int)ep->a_text, offset,
#else
(int)ep->a_text, (off_t)sizeof (struct exec),
#endif
2, (int *)0);
#endif /* VFS */
u.u_procp->p_flag &= ~SKEEP;
}
#ifdef P0INVALID
settprot(RO, pziv);
#else
settprot(RO);
#endif
xp->x_flag |= XWRIT;
xp->x_flag &= ~XLOAD;
XUNLOCK(xp);
}
/*
* Lock and unlock a text segment from swapping
*/
xlock(xp)
register struct text *xp;
{
X_LOCK(xp);
}
/*
* Wait for xp to be unlocked if it is currently locked.
*/
xwait(xp)
register struct text *xp;
{
X_LOCK(xp);
XUNLOCK(xp);
}
xunlock(xp)
register struct text *xp;
{
XUNLOCK(xp);
}
/*
* Decrement the in-core usage count of a shared text segment,
* which must be locked. When the count drops to zero,
* free the core space.
*/
xccdec(xp, p)
register struct text *xp;
register struct proc *p;
{
if (--xp->x_ccount == 0) {
if (xp->x_flag & XWRIT) {
vsswap(p, tptopte(p, 0), CTEXT, 0, (int)xp->x_size,
(struct dmap *)0);
#ifdef VFS
if (xp->x_flag & XPAGV)
#else
if (xp->x_flag & XPAGI)
#endif /* VFS */
(void)swap(p, xp->x_ptdaddr,
(caddr_t)tptopte(p, 0),
(int)xp->x_size * sizeof (struct pte),
#ifdef VFS
B_WRITE, B_PAGET, swapdev_vp, 0);
#else
B_WRITE, B_PAGET, swapdev, 0);
#endif /* VFS */
xp->x_flag &= ~XWRIT;
} else
xp->x_rssize -= vmemfree(tptopte(p, 0),
(int)xp->x_size);
if (xp->x_rssize != 0)
panic("text rssize");
}
}
/*
* Detach a process from the in-core text.
* External interface to xccdec, used when swapping out a process.
*/
xdetach(xp, p)
register struct text *xp;
struct proc *p;
{
if (xp && xp->x_ccount != 0) {
X_LOCK(xp);
xccdec(xp, p);
#ifndef ibm032
xunlink(p);
#else ibm032
xunlink(p, 0);
#endif ibm032
XUNLOCK(xp);
}
}
/*
* Free the swap image of all unused saved-text text segments
* which are from virtual filesystem vfsp (used by umount system call).
*/
#ifdef VFS
xumount(vfsp)
register struct vfs *vfsp;
{
register struct text *xp;
for (xp = text; xp < textNTEXT; xp++)
if (xp->x_vptr != NULL && (xp->x_vptr->v_vfsp == vfsp ||
vfsp == NULL)) {
xuntext(xp);
}
if (vfsp != NULL)
mpurgevfs(vfsp);
}
/*
* remove a shared text segment from the text table, if possible.
*/
xrele(vp)
register struct vnode *vp;
{
if (vp->v_flag & VTEXT)
xuntext(vp->v_text);
}
#else
xumount(dev)
register dev_t dev;
{
register struct text *xp;
for (xp = text; xp < textNTEXT; xp++)
if (xp->x_iptr != NULL &&
(dev == xp->x_iptr->i_dev || dev == NODEV))
xuntext(xp);
}
/*
* remove a shared text segment from the text table, if possible.
*/
xrele(ip)
register struct inode *ip;
{
if (ip->i_flag & ITEXT)
xuntext(ip->i_text);
}
#endif /* VFS */
/*
* remove text image from the text table.
* the use count must be zero.
*/
xuntext(xp)
register struct text *xp;
{
#ifdef VFS
register struct vnode *vp;
#else
register struct inode *ip;
#endif /* VFS */
X_LOCK(xp);
if (xp->x_count == 0) {
#ifdef VFS
vp = xp->x_vptr;
xp->x_vptr = (struct vnode *)0;
#else
ip = xp->x_iptr;
xp->x_iptr = NULL;
#endif /* VFS */
if (!xp->x_size) panic("empty text");
vsxfree(xp, ctod(xp->x_size));
xp->x_size = 0;
#ifdef VFS
vp->v_flag &= ~(VTEXT | VTEXTMOD);
vp->v_text = NULL;
VN_RELE(vp);
#else
ip->i_flag &= ~ITEXT;
ip->i_text = NULL;
irele(ip);
#endif /* VFS */
if (xp->x_back == NULL);
else if (xcache--, xp == x_lru) {
FREE_CACHE_LRU(xp,"xuntext");
goto done;
}
else {
ALLOC(xp);
}
FREE_AT_HEAD(xp);
}
/* xuntext always leaves its argument in the free-list. */
done:
XUNLOCK(xp);
}
/*
* Add a process to those sharing a text segment by
* getting the page tables and then linking to x_caddr.
*/
xlink(p)
register struct proc *p;
{
register struct text *xp = p->p_textp;
if (xp == 0)
return;
vinitpt(p);
p->p_xlink = xp->x_caddr;
xp->x_caddr = p;
xp->x_ccount++;
#ifdef ibm032
/* switch to new address space for shared text */
p->p_sid0 = make410sid( xp );
if( p == u.u_procp )
set_segreg( 0, p->p_sid0 );
#endif ibm032
}
#ifndef ibm032
xunlink(p)
#else ibm032
xunlink(p, isxrepl)
#endif ibm032
register struct proc *p;
{
register struct text *xp = p->p_textp;
register struct proc *q;
if (xp == 0)
return;
#ifdef ibm032
/* switch from address space for shared text */
if (isxrepl==0) {
p->p_sid0 = makeP0sid(p);
if (p == u.u_procp)
set_segreg(0, p->p_sid0);
}
#endif ibm032
if (xp->x_caddr == p) {
xp->x_caddr = p->p_xlink;
p->p_xlink = 0;
return;
}
for (q = xp->x_caddr; q->p_xlink; q = q->p_xlink)
if (q->p_xlink == p) {
q->p_xlink = p->p_xlink;
p->p_xlink = 0;
return;
}
panic("lost text");
}
/*
* Replace p by q in a text incore linked list.
* Used by vfork(), internally.
*/
xrepl(p, q)
struct proc *p, *q;
{
register struct text *xp = q->p_textp;
if (xp == 0)
return;
#ifndef ibm032
xunlink(p);
#else ibm032
xunlink(p, 1);
#endif ibm032
q->p_xlink = xp->x_caddr;
xp->x_caddr = q;
}
#ifdef VFS
int xkillcnt = 0;
/*
* Invalidate the text associated with vp.
* Purge in core cache of pages associated with vp and kill all active
* processes.
*/
xinval(vp)
register struct vnode *vp;
{
register struct text *xp;
register struct proc *p;
mpurge(vp);
for (xp = text; xp < textNTEXT; xp++) {
if ((xp->x_flag & XPAGV) && (xp->x_vptr == vp)) {
for (p = xp->x_caddr; p; p = p->p_xlink) {
/*
* swkill without uprintf
*/
printf(
"pid %d killed due to text modification\n",
p->p_pid);
psignal(p, SIGKILL);
p->p_flag |= SULOCK;
xkillcnt++;
}
break;
}
}
}
#endif /* VFS */
