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Below is a warmed up version of a patch originally done by Werner Almesberger (see http://tinyurl.com/25zra) to replace the MAX_MAP_COUNT limit with a sysctl variable. I thought this had gone into the tree a long time ago but alas it has not and as luck would have it, the hard limit bit someone today once again with a large app on a large machine. Here is a small test app: ----------------------------------------------------------------- #include <stdio.h> #include <stdlib.h> #include <sys/mman.h> int main (int argc, char **argv) { long n = 0; printf ("Starting mmap test...\n"); while (1) if (mmap (0, 1, (n++ & 1) ? PROT_READ : PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0) == MAP_FAILED) { printf ("Failed after %ld successful maps\n", n - 1); exit (0); } return -1; } ----------------------------------------------------------------- After applying the patch, I was able to do 20,000,000 successful maps while consuming about 3.6GB of memory (~ 180 bytes/map) which matches well enough with the actual vm_area_struct size of 128 bytes. If I set the max_map_count insanely high, the above test keeps running until we're out of memory and then the OOM killer kicks in. Basically: no surprises. Please consider for inclusion. Thanks, --david ===== Documentation/sysctl/vm.txt 1.11 vs edited ===== --- 1.11/Documentation/sysctl/vm.txt Tue Jan 20 17:58:52 2004 +++ edited/Documentation/sysctl/vm.txt Fri Mar 26 21:04:47 2004 @@ -22,6 +22,7 @@ - dirty_background_ratio - dirty_expire_centisecs - dirty_writeback_centisecs +- max_map_count - min_free_kbytes ============================================================== @@ -74,6 +75,21 @@ The number of pages the kernel reads in at once is equal to 2 ^ page-cluster. Values above 2 ^ 5 don't make much sense for swap because we only cluster swap data in 32-page groups. + +============================================================== + +max_map_count: + +This file contains the maximum number of memory map areas a process +may have. Memory map areas are used as a side-effect of calling +malloc, directly by mmap and mprotect, and also when loading shared +libraries. + +While most applications need less than a thousand maps, certain +programs, particularly malloc debuggers, may consume lots of them, +e.g., up to one or two maps per allocation. + +The default value is 65536. ============================================================== ===== include/linux/sched.h 1.170 vs edited ===== --- 1.170/include/linux/sched.h Fri Mar 19 20:31:17 2004 +++ edited/include/linux/sched.h Fri Mar 26 21:16:57 2004 @@ -179,7 +179,9 @@ struct namespace; /* Maximum number of active map areas.. This is a random (large) number */ -#define MAX_MAP_COUNT (65536) +#define DEFAULT_MAX_MAP_COUNT 65536 + +extern int sysctl_max_map_count; #include <linux/aio.h> ===== include/linux/sysctl.h 1.60 vs edited ===== --- 1.60/include/linux/sysctl.h Wed Mar 10 12:07:02 2004 +++ edited/include/linux/sysctl.h Fri Mar 26 21:06:40 2004 @@ -158,6 +158,7 @@ VM_SWAPPINESS=19, /* Tendency to steal mapped memory */ VM_LOWER_ZONE_PROTECTION=20,/* Amount of protection of lower zones */ VM_MIN_FREE_KBYTES=21, /* Minimum free kilobytes to maintain */ + VM_MAX_MAP_COUNT=22, /* int: Maximum number of active map areas per address-space */ }; ===== kernel/sysctl.c 1.58 vs edited ===== --- 1.58/kernel/sysctl.c Wed Mar 24 10:52:11 2004 +++ edited/kernel/sysctl.c Fri Mar 26 21:14:53 2004 @@ -736,6 +736,14 @@ .strategy = &sysctl_intvec, .extra1 = &zero, }, + { + .ctl_name = VM_MAX_MAP_COUNT, + .procname = "max_map_count", + .data = &sysctl_max_map_count, + .maxlen = sizeof(sysctl_max_map_count), + .mode = 0644, + .proc_handler = &proc_dointvec + }, { .ctl_name = 0 } }; ===== mm/mmap.c 1.99 vs edited ===== --- 1.99/mm/mmap.c Mon Mar 15 22:50:13 2004 +++ edited/mm/mmap.c Fri Mar 26 21:14:40 2004 @@ -54,10 +54,12 @@ int sysctl_overcommit_memory = 0; /* default is heuristic overcommit */ int sysctl_overcommit_ratio = 50; /* default is 50% */ +int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT; atomic_t vm_committed_space = ATOMIC_INIT(0); EXPORT_SYMBOL(sysctl_overcommit_memory); EXPORT_SYMBOL(sysctl_overcommit_ratio); +EXPORT_SYMBOL(sysctl_max_map_count); EXPORT_SYMBOL(vm_committed_space); /* @@ -512,7 +514,7 @@ return -EINVAL; /* Too many mappings? */ - if (mm->map_count > MAX_MAP_COUNT) + if (mm->map_count > sysctl_max_map_count) return -ENOMEM; /* Obtain the address to map to. we verify (or select) it and ensure @@ -1197,7 +1199,7 @@ struct vm_area_struct *new; struct address_space *mapping = NULL; - if (mm->map_count >= MAX_MAP_COUNT) + if (mm->map_count >= sysctl_max_map_count) return -ENOMEM; new = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); @@ -1375,7 +1377,7 @@ > current->rlim[RLIMIT_AS].rlim_cur) return -ENOMEM; - if (mm->map_count > MAX_MAP_COUNT) + if (mm->map_count > sysctl_max_map_count) return -ENOMEM; if (security_vm_enough_memory(len >> PAGE_SHIFT)) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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