Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
On Fri, Aug 19, 2005 at 11:14:39PM -0400, Chuck Ebbert wrote: > Someone complained about the docs for vm_overcommit_memory being wrong. > This patch copies the text from the vm documentation into procfs. > Please apply. >... Do we really need two copies of the same text? Couldn't you instead write some kind of "please look at Documentation/vm/overcommit-accounting"? > Chuck cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
On Fri, 19 Aug 2005 20:24:26 -0700, Andrew Morton wrote: > Chuck Ebbert <[EMAIL PROTECTED]> wrote: > > > > +Controls overcommit of system memory: > > It should explain what "overcommit" is. Here is an improved version. Signed-off-by: Chuck Ebbert <[EMAIL PROTECTED]> Documentation/filesystems/proc.txt | 42 - 1 files changed, 32 insertions(+), 10 deletions(-) --- 2.6.13-rc6c.orig/Documentation/filesystems/proc.txt +++ 2.6.13-rc6c/Documentation/filesystems/proc.txt @@ -1240,16 +1240,38 @@ swap-intensive. overcommit_memory - -This file contains one value. The following algorithm is used to decide if -there's enough memory: if the value of overcommit_memory is positive, then -there's always enough memory. This is a useful feature, since programs often -malloc() huge amounts of memory 'just in case', while they only use a small -part of it. Leaving this value at 0 will lead to the failure of such a huge -malloc(), when in fact the system has enough memory for the program to run. - -On the other hand, enabling this feature can cause you to run out of memory -and thrash the system to death, so large and/or important servers will want to -set this value to 0. +Controls overcommit of system memory, possibly allowing processes +to allocate (but not use) more memory than is actually available. + + +0 - Heuristic overcommit handling. Obvious overcommits of + address space are refused. Used for a typical system. It + ensures a seriously wild allocation fails while allowing + overcommit to reduce swap usage. root is allowed to + allocate slighly more memory in this mode. This is the + default. + +1 - Always overcommit. Appropriate for some scientific + applications. + +2 - Don't overcommit. The total address space commit + for the system is not permitted to exceed swap plus a + configurable percentage (default is 50) of physical RAM. + Depending on the percentage you use, in most situations + this means a process will not be killed while attempting + to use already-allocated memory but will receive errors + on memory allocation as appropriate. + +overcommit_ratio + + +Percentage of physical memory size to include in overcommit calculations +(see above.) + +Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100) + + swapspace = total size of all swap areas + physmem = size of physical memory in system nr_hugepages and hugetlb_shm_group -- __ Chuck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
On Fri, 19 Aug 2005 20:24:26 -0700, Andrew Morton wrote: Chuck Ebbert [EMAIL PROTECTED] wrote: +Controls overcommit of system memory: It should explain what overcommit is. Here is an improved version. Signed-off-by: Chuck Ebbert [EMAIL PROTECTED] Documentation/filesystems/proc.txt | 42 - 1 files changed, 32 insertions(+), 10 deletions(-) --- 2.6.13-rc6c.orig/Documentation/filesystems/proc.txt +++ 2.6.13-rc6c/Documentation/filesystems/proc.txt @@ -1240,16 +1240,38 @@ swap-intensive. overcommit_memory - -This file contains one value. The following algorithm is used to decide if -there's enough memory: if the value of overcommit_memory is positive, then -there's always enough memory. This is a useful feature, since programs often -malloc() huge amounts of memory 'just in case', while they only use a small -part of it. Leaving this value at 0 will lead to the failure of such a huge -malloc(), when in fact the system has enough memory for the program to run. - -On the other hand, enabling this feature can cause you to run out of memory -and thrash the system to death, so large and/or important servers will want to -set this value to 0. +Controls overcommit of system memory, possibly allowing processes +to allocate (but not use) more memory than is actually available. + + +0 - Heuristic overcommit handling. Obvious overcommits of + address space are refused. Used for a typical system. It + ensures a seriously wild allocation fails while allowing + overcommit to reduce swap usage. root is allowed to + allocate slighly more memory in this mode. This is the + default. + +1 - Always overcommit. Appropriate for some scientific + applications. + +2 - Don't overcommit. The total address space commit + for the system is not permitted to exceed swap plus a + configurable percentage (default is 50) of physical RAM. + Depending on the percentage you use, in most situations + this means a process will not be killed while attempting + to use already-allocated memory but will receive errors + on memory allocation as appropriate. + +overcommit_ratio + + +Percentage of physical memory size to include in overcommit calculations +(see above.) + +Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100) + + swapspace = total size of all swap areas + physmem = size of physical memory in system nr_hugepages and hugetlb_shm_group -- __ Chuck - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
On Fri, Aug 19, 2005 at 11:14:39PM -0400, Chuck Ebbert wrote: Someone complained about the docs for vm_overcommit_memory being wrong. This patch copies the text from the vm documentation into procfs. Please apply. ... Do we really need two copies of the same text? Couldn't you instead write some kind of please look at Documentation/vm/overcommit-accounting? Chuck cu Adrian -- Is there not promise of rain? Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. Only a promise, Lao Er said. Pearl S. Buck - Dragon Seed - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
Chuck Ebbert <[EMAIL PROTECTED]> wrote: > > +Controls overcommit of system memory: It should explain what "overcommit" is. > + > +0 - Heuristic overcommit handling. Obvious overcommits of > +address space are refused. Used for a typical system. It > +ensures a seriously wild allocation fails while allowing > +overcommit to reduce swap usage. root is allowed to > +allocate slighly more memory in this mode. This is the > +default. > + > +1 - Always overcommit. Appropriate for some scientific > +applications. > + > +2 - Don't overcommit. The total address space commit > +for the system is not permitted to exceed swap + a > +configurable percentage (default is 50) of physical RAM. Configurable how? > +Depending on the percentage you use, in most situations > +this means a process will not be killed while accessing > +pages but will receive errors on memory allocation as > +appropriate. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 2.6.13-rc6] docs: fix misinformation about overcommit_memory
Chuck Ebbert [EMAIL PROTECTED] wrote: +Controls overcommit of system memory: It should explain what overcommit is. + +0 - Heuristic overcommit handling. Obvious overcommits of +address space are refused. Used for a typical system. It +ensures a seriously wild allocation fails while allowing +overcommit to reduce swap usage. root is allowed to +allocate slighly more memory in this mode. This is the +default. + +1 - Always overcommit. Appropriate for some scientific +applications. + +2 - Don't overcommit. The total address space commit +for the system is not permitted to exceed swap + a +configurable percentage (default is 50) of physical RAM. Configurable how? +Depending on the percentage you use, in most situations +this means a process will not be killed while accessing +pages but will receive errors on memory allocation as +appropriate. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
