On 02/13/2012 08:07 PM, Zhouping Liu wrote: > > There are two tunables overcommit_memory and overcommit_ratio under > /proc/sys/vm/, which can control memory overcommitment. > > The overcommit_memory contains a flag that enables memory > overcommitment, it has three values: > - When this flag is 0, the kernel attempts to estimate the amount > of free memory left when userspace requests more memory. > - When this flag is 1, the kernel pretends there is always enough > memory until it actually runs out. > - When this flag is 2, the kernel uses a "never overcommit" policy > that attempts to prevent any overcommit of memory. > > The overcommit_ratio tunable defines the amount by which the kernel > overextends its memory resources in the event that overcommit_memory > is set to the value of 2. The value in this file represents a > percentage added to the amount of actual RAM in a system when > considering whether to grant a particular memory request. > The general formula for this tunable is: > CommitLimit = SwapTotal + MemTotal * overcommit_ratio > CommitLimit, SwapTotal and MemTotal can read from /proc/meminfo. > > The program is designed to test the two tunables: > > When overcommit_memory = 0, allocatable memory can't overextends > the amount of free memory. I choose the three cases: > a. less than free_total: free_total / 2, alloc should pass. > b. greater than free_total: free_total * 2, alloc should fail. > c. equal to sum_total: sum_tatal, alloc should fail > > When overcommit_memory = 1, it can alloc enough much memory, I > choose the three cases: > a. less than sum_total: sum_total / 2, alloc should pass > b. equal to sum_total: sum_total, alloc should pass > c. greater than sum_total: sum_total * 2, alloc should pass > *note: sum_total = SwapTotal + MemTotal > > When overcommit_memory = 2, the total virtual address space on > the system is limited to CommitLimit(Swap+RAM*overcommit_ratio) > commit_left(allocatable memory) = CommitLimit - Committed_AS > a. less than commit_left: commit_left / 2, alloc should pass > b. greater than commit_left: commit_left * 2, alloc should fail > c. overcommit limit: CommitLimit, alloc should fail > *note: CommitLimit is the current overcommit limit. > Committed_AS is the amount of memory that system has used. > it couldn't choose 'equal to commit_left' as a case, because > commit_left rely on Committed_AS, but the Committed_AS is not stable. > > References: > - Documentation/sysctl/vm.txt > - Documentation/vm/overcommit-accounting > > Signed-off-by: Zhouping Liu <[email protected]> > --- > hi, all > > v1 -> v2: used SAFE_STRTOL macro. > > please review the patch, any comments are welcome. > > runtest/mm | 7 + > testcases/kernel/mem/tunable/Makefile | 43 ++++ > testcases/kernel/mem/tunable/overcommit_memory.c | 275 > ++++++++++++++++++++++ > 3 files changed, 325 insertions(+), 0 deletions(-) > create mode 100644 testcases/kernel/mem/tunable/Makefile > create mode 100644 testcases/kernel/mem/tunable/overcommit_memory.c > Acked-by: Caspar Zhang <[email protected]>
------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
