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Add a facility allowing processes to inform the VM subsystem they are

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critical and should not be killed when pageout is looking for more
memory pages in all the wrong places.

Reviewed by:	arch@
Sponsored by:	St. Bernard Software
This commit is contained in:
Wes Peters 2003-03-31 21:09:57 +00:00
parent 59f47d29b7
commit f4cf2141f6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=112881
5 changed files with 28 additions and 1 deletions
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9
lib/libc/sys/madvise.2
View File

@ -117,6 +117,12 @@ system calls.
Region is not included in a core file.
.It Dv MADV_CORE
Include region in a core file.
.It Dv MADV_PROTECT
Informs the VM system this process should not be killed when the
swap space is exhausted.
The process must have superuser privileges.
This should be used judiciously in processes that must remain running
for the system to properly function.
.El
.Sh RETURN VALUES
.Rv -std madvise
@ -131,6 +137,9 @@ The virtual address range specified by the
and
.Fa len
arguments is not valid.
.It Bq Er EPERM
.Dv MADV_PROTECT
was specified and the process does not have superuser privileges.
.El
.Sh SEE ALSO
.Xr mincore 2 ,

1
sys/sys/mman.h
View File

@ -124,6 +124,7 @@
#define MADV_AUTOSYNC 7 /* revert to default flushing strategy */
#define MADV_NOCORE 8 /* do not include these pages in a core file */
#define MADV_CORE 9 /* revert to including pages in a core file */
#define MADV_PROTECT 10 /* protect process from pageout kill */
/*
* Return bits from mincore

1
sys/sys/proc.h
View File

@ -629,6 +629,7 @@ struct proc {
#define P_EXEC 0x04000 /* Process called exec. */
#define P_THREADED 0x08000 /* Process is using threads. */
#define P_CONTINUED 0x10000 /* Proc has continued from a stopped state. */
#define P_PROTECTED 0x20000 /* Do not kill on memory overcommit. */
/* flags that control how threads may be suspended for some reason */
#define P_STOPPED_SIG 0x20000 /* Stopped due to SIGSTOP/SIGTSTP */

15
sys/vm/vm_mmap.c
View File

@ -752,7 +752,22 @@ madvise(td, uap)
{
vm_offset_t start, end;
vm_map_t map;
struct proc *p;
int error;
/*
* Check for our special case, advising the swap pager we are
* "immortal."
*/
if (uap->behav == MADV_PROTECT) {
p = td->td_proc;
PROC_LOCK(p);
error = suser(td);
if (error == 0)
p->p_flag |= P_PROTECTED;
PROC_UNLOCK(p);
return (error);
}
/*
* Check for illegal behavior
*/

3
sys/vm/vm_pageout.c
View File

@ -1184,9 +1184,10 @@ vm_pageout_scan(int pass)
if (PROC_TRYLOCK(p) == 0)
continue;
/*
* if this is a system process, skip it
* If this is a system or protected process, skip it.
*/
if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
(p->p_flag & P_PROTECTED) ||
((p->p_pid < 48) && (vm_swap_size != 0))) {
PROC_UNLOCK(p);
continue;