lkml.org 
[lkml]   [2013]   [May]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] Make batch size for memory accounting configured according to size of memory
Hi Tim,
On 04/30/2013 01:12 AM, Tim Chen wrote:
> Currently the per cpu counter's batch size for memory accounting is
> configured as twice the number of cpus in the system. However,
> for system with very large memory, it is more appropriate to make it
> proportional to the memory size per cpu in the system.
>
> For example, for a x86_64 system with 64 cpus and 128 GB of memory,
> the batch size is only 2*64 pages (0.5 MB). So any memory accounting
> changes of more than 0.5MB will overflow the per cpu counter into
> the global counter. Instead, for the new scheme, the batch size
> is configured to be 0.4% of the memory/cpu = 8MB (128 GB/64 /256),

If large batch size will lead to global counter more inaccurate?

> which is more inline with the memory size.
>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> ---
> mm/mmap.c | 13 ++++++++++++-
> mm/nommu.c | 13 ++++++++++++-
> 2 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 0db0de1..082836e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -89,6 +89,7 @@ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
> * other variables. It can be updated by several CPUs frequently.
> */
> struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
> +int vm_committed_batchsz ____cacheline_aligned_in_smp;
>
> /*
> * The global memory commitment made in the system can be a metric
> @@ -3090,10 +3091,20 @@ void mm_drop_all_locks(struct mm_struct *mm)
> /*
> * initialise the VMA slab
> */
> +static inline int mm_compute_batch(void)
> +{
> + int nr = num_present_cpus();
> +
> + /* batch size set to 0.4% of (total memory/#cpus) */
> + return (int) (totalram_pages/nr) / 256;
> +}
> +
> void __init mmap_init(void)
> {
> int ret;
>
> - ret = percpu_counter_init(&vm_committed_as, 0);
> + vm_committed_batchsz = mm_compute_batch();
> + ret = percpu_counter_and_batch_init(&vm_committed_as, 0,
> + &vm_committed_batchsz);
> VM_BUG_ON(ret);
> }
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 2f3ea74..a87a99c 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -59,6 +59,7 @@ unsigned long max_mapnr;
> unsigned long num_physpages;
> unsigned long highest_memmap_pfn;
> struct percpu_counter vm_committed_as;
> +int vm_committed_batchsz;
> int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
> int sysctl_overcommit_ratio = 50; /* default is 50% */
> int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
> @@ -526,11 +527,21 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> /*
> * initialise the VMA and region record slabs
> */
> +static inline int mm_compute_batch(void)
> +{
> + int nr = num_present_cpus();
> +
> + /* batch size set to 0.4% of (total memory/#cpus) */
> + return (int) (totalram_pages/nr) / 256;
> +}
> +
> void __init mmap_init(void)
> {
> int ret;
>
> - ret = percpu_counter_init(&vm_committed_as, 0);
> + vm_committed_batchsz = mm_compute_batch();
> + ret = percpu_counter_and_batch_init(&vm_committed_as, 0,
> + &vm_committed_batchsz);
> VM_BUG_ON(ret);
> vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC);
> }



\
 
 \ /
  Last update: 2013-05-01 07:41    [W:0.115 / U:0.708 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site