* Re: shm and locked pages
[not found] <199712010925.KAA09786@marlene.neurologie.uni-duesseldorf.de>
@ 1997-12-01 20:33 ` Dr. Werner Fink
0 siblings, 0 replies; only message in thread
From: Dr. Werner Fink @ 1997-12-01 20:33 UTC (permalink / raw)
To: weule; +Cc: linux-kernel, linux-mm
> Hello Kernel-Developers!
Nice idea for stopping foolish syscalls like makeing hugh amount of
memory non-swappable. But the calculation of your limits is not a win ...
please do not use floats within the kernel ;)
Nevertheless, the idea may explain and solve _some_ seen memory leaks due
locked but never unlocked shm's.
Werner
>
> If root is locking more shm pages to physical memory than the computer
> has, the system stopps running because all other pages are swapped out.
> To fix this, I patched ipc/shm.c and decided to limit the locked pages
> to
> totalram - sqrt(totalram*8MB):
>
> /*
> * Maximal locked shared memory:
> * totalmem - sqrt(8MB*totalram) if totalram > 8MB
> *
> * Exampes:
> *
> * totalram: 8 12.0 16.0 18 20.0 24.0 32 50 64.0 72 128 256
> * never locked: 8 9.8 11.3 12 12.6 13.9 16 20 22.6 24 32 45
> * max locked: 0 2.2 4.7 6 7.4 10.1 16 30 41.4 48 96 211
> *
> * The formular seem reasonable for me.
> * t-sqrt(8MB*t)>m <=3D=3D> (t-m)*(t-m)-8MB*t>0
> *
> * J"org Weule (weule@acm.org)
> */
>
> If a program locking half the pages hangs and a second one is started,
> the second will not lock the other half of the memory and the system is =
> still
> up. shm_lock.c is a program to test the number of pages one can lock.
>
> The number val.totalram (struct sys_meminfo) may be replaced by =
> num_physpages
> at linux-2.1.xx in future releases.
>
> Hope this helps
>
> J"org
> -------------------------------------------------------------------------=
> ------
> J=F6rg Weule - weule@uni-duesseldorf.de - =
> http://www.cs.uni-duesseldorf.de/~weule
> --700c_66f6-60f5_4b48-54f0_ec4
> Content-Type: application/octet-stream; name=shm.c.diff-2.0.29
> Content-Transfer-Encoding: 7bit
> Content-MD5: IEgTrE1FgVh9D0rLd+A72Q==
> Content-Description: shm.c.diff-2.0.29
> Content-Disposition: attachment; filename=shm.c.diff-2.0.29
>
> --- shm.c.orig Fri Nov 28 15:43:41 1997
> +++ shm.c Mon Dec 1 10:05:16 1997
> @@ -2,6 +2,7 @@
> * linux/ipc/shm.c
> * Copyright (C) 1992, 1993 Krishna Balasubramanian
> * Many improvements/fixes by Bruno Haible.
> + * Limit of locked pages: J"org Weule (weule@acm.org), Nov 1997.
> * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
> */
>
> @@ -28,6 +29,7 @@
> static pte_t shm_swap_in(struct vm_area_struct *, unsigned long, unsigned long);
>
> static int shm_tot = 0; /* total number of shared memory pages */
> +static int shm_totlock = 0; /* total number of locked shared memory pages */
> static int shm_rss = 0; /* number of shared memory pages that are in memory */
> static int shm_swp = 0; /* number of shared memory pages that are in swap */
> static int max_shmid = 0; /* every used id is <= max_shmid */
> @@ -47,7 +49,7 @@
>
> for (id = 0; id < SHMMNI; id++)
> shm_segs[id] = (struct shmid_ds *) IPC_UNUSED;
> - shm_tot = shm_rss = shm_seq = max_shmid = used_segs = 0;
> + shm_tot = shm_totlock = shm_rss = shm_seq = max_shmid = used_segs = 0;
> shm_lock = NULL;
> return;
> }
> @@ -191,6 +193,7 @@
> shm_swp--;
> }
> }
> + if (shp->shm_perm.mode & SHM_LOCKED) shm_totlock -= numpages ;
> kfree(shp->shm_pages);
> shm_tot -= numpages;
> kfree(shp);
> @@ -289,6 +292,7 @@
> if (!(ipcp->mode & SHM_LOCKED))
> return -EINVAL;
> ipcp->mode &= ~SHM_LOCKED;
> + shm_totlock -= shp->shm_npages;
> break;
> case SHM_LOCK:
> /* Allow superuser to lock segment in memory */
> @@ -298,7 +302,31 @@
> return -EPERM;
> if (ipcp->mode & SHM_LOCKED)
> return -EINVAL;
> + /*
> + * Maximal locked shared memory:
> + * totalmem - sqrt(8MB*totalram) if totalram > 8MB
> + *
> + * Exampes:
> + *
> + * totalram: 8 12.0 16.0 18 20.0 24.0 32 50 64.0 72 128 256
> + * never locked: 8 9.8 11.3 12 12.6 13.9 16 20 22.6 24 32 45
> + * max locked: 0 2.2 4.7 6 7.4 10.1 16 30 41.4 48 96 211
> + *
> + * The formular seem reasonable for me.
> + * t-sqrt(8MB*t)>m <==> (t-m)*(t-m)-8MB*t>0
> + *
> + * J"org Weule (weule@acm.org)
> + */
> + { struct sysinfo val ;
> + double d ;
> + si_meminfo(&val);
> + d = ( shp->shm_npages + shm_totlock ) * PAGE_SIZE ;
> + d -= val.totalram ;
> + d = d * d / (1024UL*8192UL) - val.totalram ;
> + if ( val.totalram < (8192UL*1024UL) || d < 0.0 ) return -EPERM ;
> + }
> ipcp->mode |= SHM_LOCKED;
> + shm_totlock += shp->shm_npages;
> break;
> case IPC_STAT:
> if (ipcperms (ipcp, S_IRUGO))
> --700c_66f6-60f5_4b48-54f0_ec4
> Content-Type: application/octet-stream; name=shm.c.diff-2.1.66
> Content-Transfer-Encoding: 7bit
> Content-MD5: qS9y3i3sA7ImutlYngf/iw==
> Content-Description: shm.c.diff-2.1.66
> Content-Disposition: attachment; filename=shm.c.diff-2.1.66
>
> --- shm.c.orig Mon Dec 1 09:34:44 1997
> +++ shm.c Mon Dec 1 10:16:29 1997
> @@ -2,6 +2,7 @@
> * linux/ipc/shm.c
> * Copyright (C) 1992, 1993 Krishna Balasubramanian
> * Many improvements/fixes by Bruno Haible.
> + * Limit of locked pages: J"org Weule (weule@acm.org), Nov 1997.
> * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
> */
>
> @@ -32,6 +33,7 @@
> static pte_t shm_swap_in(struct vm_area_struct *, unsigned long, unsigned long);
>
> static int shm_tot = 0; /* total number of shared memory pages */
> +static int shm_totlock = 0; /* total number of locked shared memory pages */
> static int shm_rss = 0; /* number of shared memory pages that are in memory */
> static int shm_swp = 0; /* number of shared memory pages that are in swap */
> static int max_shmid = 0; /* every used id is <= max_shmid */
> @@ -51,7 +53,7 @@
>
> for (id = 0; id < SHMMNI; id++)
> shm_segs[id] = (struct shmid_ds *) IPC_UNUSED;
> - shm_tot = shm_rss = shm_seq = max_shmid = used_segs = 0;
> + shm_tot = shm_totlock = shm_rss = shm_seq = max_shmid = used_segs = 0;
> shm_lock = NULL;
> return;
> }
> @@ -201,6 +203,7 @@
> shm_swp--;
> }
> }
> + if (shp->shm_perm.mode & SHM_LOCKED) shm_totlock -= numpages ;
> kfree(shp->shm_pages);
> shm_tot -= numpages;
> kfree(shp);
> @@ -312,6 +315,7 @@
> if (!(ipcp->mode & SHM_LOCKED))
> goto out;
> ipcp->mode &= ~SHM_LOCKED;
> + shm_totlock -= shp->shm_npages;
> break;
> case SHM_LOCK:
> /* Allow superuser to lock segment in memory */
> @@ -323,6 +327,31 @@
> err = -EINVAL;
> if (ipcp->mode & SHM_LOCKED)
> goto out;
> + /*
> + * Maximal locked shared memory:
> + * totalmem - sqrt(8MB*totalram) if totalram > 8MB
> + *
> + * Exampes:
> + *
> + * totalram: 8 12.0 16.0 18 20.0 24.0 32 50 64.0 72 128 256
> + * never locked: 8 9.8 11.3 12 12.6 13.9 16 20 22.6 24 32 45
> + * max locked: 0 2.2 4.7 6 7.4 10.1 16 30 41.4 48 96 211
> + *
> + * The formular seem reasonable for me.
> + * t-sqrt(8MB*t)>m <==> (t-m)*(t-m)-8MB*t>0
> + *
> + * J"org Weule (weule@acm.org)
> + */
> +
> + { struct sysinfo val ;
> + double d ;
> + si_meminfo(&val);
> + d = ( shp->shm_npages + shm_totlock ) * PAGE_SIZE ;
> + d -= val.totalram ;
> + d = d * d / (1024UL*8192UL) - val.totalram ;
> + if ( val.totalram < (8192UL*1024UL) || d < 0.0 ) return -EPERM ;
> + }
> + shm_totlock += shp->shm_npages;
> ipcp->mode |= SHM_LOCKED;
> break;
> case IPC_STAT:
> --700c_66f6-60f5_4b48-54f0_ec4
> Content-Type: text/plain; charset=ISO-8859-1; name=shm_lock.c
> Content-Transfer-Encoding: 7bit
> Content-MD5: Bzn0f2BvObYZBLIoe8l3SQ==
> Content-Description: shm_lock.c
> Content-Disposition: attachment; filename=shm_lock.c
> X-Sun-Data-Type: c-file
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/ipc.h>
> #include <sys/shm.h>
> #include <sys/wait.h>
> #include <sys/stat.h>
> #include <fcntl.h>
>
> /*
> * Tries to lock 200 MB of memory and sleeps the number of seconds
> * specified by the first parameter. root can test shm with this program.
> * (C)opyright by J"org Weule (weule@acm.org), Nov 1997.
> */
>
> int s[100];
> char*(p[100]);
>
> int main(int argc,char*argv[]){
> int f ;
> int pid , st ;
> int i , tot = 0 ;
> key_t k = IPC_PRIVATE ;
> int n = 1024*1024*2 ;
> do {
> s[0]=shmget(k, n, (int)IPC_CREAT|0600);
> if ( s[0] < 0 ) n -= 1024 ;
> else break ;
> } while( n>1024 );
> if ( s[0] < 0 ) printf("shmget->%d\n",s[0]),perror("shmget"),exit(1);
> tot += n ;
> p[0]=shmat(s[0],NULL,0);
> if(0>=shmctl(s[0],IPC_RMID,NULL))puts("RMID 1");
> if ( shmctl(s[0],SHM_LOCK,NULL)>=0) puts("lock1");
> printf("%d\n",n);
> for ( i = 1 ; i < 100 ; i++ ){
> s[i]=shmget(k, n, (int)IPC_CREAT|0600);
> if ( s[i] < 0 ) printf("shmget->%d\n",s[i]),perror("shmget"),exit(1);
> p[i]=shmat(s[i],NULL,0);
> if(0>=shmctl(s[i],IPC_RMID,NULL))puts("RMID 1");
> if ( shmctl(s[i],SHM_LOCK,NULL)>=0) puts("lock1");
> else break ;
> tot += n ;
> printf("%20d\n",tot);
> }
> if ( argc > 1 ) sleep(atoi(argv[1]));
> else system("ipcs -m"),sleep(60);
> exit(0);
> }
>
>
> --700c_66f6-60f5_4b48-54f0_ec4--
>
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