Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 9 Nov 2000 11:20:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 9 Nov 2000 11:20:49 -0500 Received: from dfmail.f-secure.com ([194.252.6.39]:56583 "HELO dfmail.f-secure.com") by vger.kernel.org with SMTP id ; Thu, 9 Nov 2000 11:20:35 -0500 Date: Thu, 9 Nov 2000 18:30:32 +0100 (MET) From: Szabolcs Szakacsits To: Rik van Riel cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Ingo Molnar Subject: [PATCH] Reserve VM for root (was: Re: Looking for better VM) In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 8 Nov 2000, Rik van Riel wrote: > OK. This is a lot more reasonable. Just the same what was in my first in email. > I'm actually looking into putting non-overcommit as a configurable > option in the kernel. Nice to hear, please make it a boot time option, not a compile time one. Also a control for how many percent the kernel can overcommit would be nice -- this is how modern Unices do. > However, this does not save you from the fact that the > system is essentially deadlocked when nothing can get > more memory and nothing goes away. I've also never said OOM killer should be disabled. In theory the non-overcommitting systems deadlock, Linux survives. Ironically usually it's just the opposite in practice. Any user can deadlock/crash Linux [default install, no quotas] but not an non-overcommitting system [root can clean up]. Here is an example code "simulating" a leaking daemon that will "deadlock" Linux even with your OOM killer patch [that is anyway *MUCH* better than the actually non-existing one in 2.2.x kernels]: main() { while(1) if (fork()) malloc(1); } With the patch below I could ssh to the host and killall the offending processes. To enable reserving VM space for root do echo -1 > /proc/sys/vm/overcommit_memory The number of reserved pages can be tuned via /proc/sys/vm/reserved, default is 5% of the RAM (note, RAM won't be reserved, but VM). BTW, I wanted to take a look at the frequently mentioned beancounter patch, here is the current state, http://www.asp-linux.com/en/products/ubpatch.shtml "Sorry, due to growing expenses for support of public version of ASPcomplete we do not provide sources till first official release." Szaka diff -ur linux.orig/include/linux/sysctl.h linux/include/linux/sysctl.h --- linux.orig/include/linux/sysctl.h Thu Nov 9 08:20:19 2000 +++ linux/include/linux/sysctl.h Thu Nov 9 06:30:11 2000 @@ -122,7 +122,8 @@ VM_PAGECACHE=7, /* struct: Set cache memory thresholds */ VM_PAGERDAEMON=8, /* struct: Control kswapd behaviour */ VM_PGT_CACHE=9, /* struct: Set page table cache parameters */ - VM_PAGE_CLUSTER=10 /* int: set number of pages to swap together */ + VM_PAGE_CLUSTER=10, /* int: set number of pages to swap together */ + VM_RESERVED=11 /* int: number of pages reserved for root */ }; diff -ur linux.orig/kernel/sysctl.c linux/kernel/sysctl.c --- linux.orig/kernel/sysctl.c Thu Nov 9 08:20:19 2000 +++ linux/kernel/sysctl.c Thu Nov 9 06:27:33 2000 @@ -37,6 +37,7 @@ extern int bdf_prm[], bdflush_min[], bdflush_max[]; extern char binfmt_java_interpreter[], binfmt_java_appletviewer[]; extern int sysctl_overcommit_memory; +extern int vm_reserved; extern int nr_queued_signals, max_queued_signals; #ifdef CONFIG_KMOD @@ -259,6 +260,8 @@ &pgt_cache_water, 2*sizeof(int), 0600, NULL, &proc_dointvec}, {VM_PAGE_CLUSTER, "page-cluster", &page_cluster, sizeof(int), 0600, NULL, &proc_dointvec}, + {VM_RESERVED, "reserved", + &vm_reserved, sizeof(int), 0600, NULL, &proc_dointvec}, {0} }; diff -ur linux.orig/mm/mmap.c linux/mm/mmap.c --- linux.orig/mm/mmap.c Thu Nov 9 08:20:19 2000 +++ linux/mm/mmap.c Thu Nov 9 08:17:10 2000 @@ -40,6 +40,7 @@ kmem_cache_t *vm_area_cachep; int sysctl_overcommit_memory; +int vm_reserved; /* Check that a process has enough memory to allocate a * new virtual mapping. @@ -59,7 +60,7 @@ long free; /* Sometimes we want to use more memory than we have. */ - if (sysctl_overcommit_memory) + if (sysctl_overcommit_memory == 1) return 1; free = buffermem >> PAGE_SHIFT; @@ -67,6 +68,8 @@ free += nr_free_pages; free += nr_swap_pages; free -= (page_cache.min_percent + buffer_mem.min_percent + 2)*num_physpages/100; + if (sysctl_overcommit_memory == -1 && current->uid && free < vm_reserved) + return 0; return free > pages; } @@ -872,6 +875,11 @@ void __init vma_init(void) { + struct sysinfo i; + + si_meminfo(&i); + vm_reserved = (i.totalram >> PAGE_SHIFT) / 20; + vm_area_cachep = kmem_cache_create("vm_area_struct", sizeof(struct vm_area_struct), 0, SLAB_HWCACHE_ALIGN, - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/