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Diffstat (limited to 'Documentation/trace/events-kmem.txt')
| -rw-r--r-- | Documentation/trace/events-kmem.txt | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/Documentation/trace/events-kmem.txt b/Documentation/trace/events-kmem.txt index 6ef2a8652e17..aa82ee4a5a87 100644 --- a/Documentation/trace/events-kmem.txt +++ b/Documentation/trace/events-kmem.txt | |||
| @@ -1,7 +1,7 @@ | |||
| 1 | Subsystem Trace Points: kmem | 1 | Subsystem Trace Points: kmem |
| 2 | 2 | ||
| 3 | The tracing system kmem captures events related to object and page allocation | 3 | The kmem tracing system captures events related to object and page allocation |
| 4 | within the kernel. Broadly speaking there are four major subheadings. | 4 | within the kernel. Broadly speaking there are five major subheadings. |
| 5 | 5 | ||
| 6 | o Slab allocation of small objects of unknown type (kmalloc) | 6 | o Slab allocation of small objects of unknown type (kmalloc) |
| 7 | o Slab allocation of small objects of known type | 7 | o Slab allocation of small objects of known type |
| @@ -9,7 +9,7 @@ within the kernel. Broadly speaking there are four major subheadings. | |||
| 9 | o Per-CPU Allocator Activity | 9 | o Per-CPU Allocator Activity |
| 10 | o External Fragmentation | 10 | o External Fragmentation |
| 11 | 11 | ||
| 12 | This document will describe what each of the tracepoints are and why they | 12 | This document describes what each of the tracepoints is and why they |
| 13 | might be useful. | 13 | might be useful. |
| 14 | 14 | ||
| 15 | 1. Slab allocation of small objects of unknown type | 15 | 1. Slab allocation of small objects of unknown type |
| @@ -34,7 +34,7 @@ kmem_cache_free call_site=%lx ptr=%p | |||
| 34 | These events are similar in usage to the kmalloc-related events except that | 34 | These events are similar in usage to the kmalloc-related events except that |
| 35 | it is likely easier to pin the event down to a specific cache. At the time | 35 | it is likely easier to pin the event down to a specific cache. At the time |
| 36 | of writing, no information is available on what slab is being allocated from, | 36 | of writing, no information is available on what slab is being allocated from, |
| 37 | but the call_site can usually be used to extrapolate that information | 37 | but the call_site can usually be used to extrapolate that information. |
| 38 | 38 | ||
| 39 | 3. Page allocation | 39 | 3. Page allocation |
| 40 | ================== | 40 | ================== |
| @@ -80,9 +80,9 @@ event indicating whether it is for a percpu_refill or not. | |||
| 80 | When the per-CPU list is too full, a number of pages are freed, each one | 80 | When the per-CPU list is too full, a number of pages are freed, each one |
| 81 | which triggers a mm_page_pcpu_drain event. | 81 | which triggers a mm_page_pcpu_drain event. |
| 82 | 82 | ||
| 83 | The individual nature of the events are so that pages can be tracked | 83 | The individual nature of the events is so that pages can be tracked |
| 84 | between allocation and freeing. A number of drain or refill pages that occur | 84 | between allocation and freeing. A number of drain or refill pages that occur |
| 85 | consecutively imply the zone->lock being taken once. Large amounts of PCP | 85 | consecutively imply the zone->lock being taken once. Large amounts of per-CPU |
| 86 | refills and drains could imply an imbalance between CPUs where too much work | 86 | refills and drains could imply an imbalance between CPUs where too much work |
| 87 | is being concentrated in one place. It could also indicate that the per-CPU | 87 | is being concentrated in one place. It could also indicate that the per-CPU |
| 88 | lists should be a larger size. Finally, large amounts of refills on one CPU | 88 | lists should be a larger size. Finally, large amounts of refills on one CPU |
| @@ -102,6 +102,6 @@ is important. | |||
| 102 | 102 | ||
| 103 | Large numbers of this event implies that memory is fragmenting and | 103 | Large numbers of this event implies that memory is fragmenting and |
| 104 | high-order allocations will start failing at some time in the future. One | 104 | high-order allocations will start failing at some time in the future. One |
| 105 | means of reducing the occurange of this event is to increase the size of | 105 | means of reducing the occurrence of this event is to increase the size of |
| 106 | min_free_kbytes in increments of 3*pageblock_size*nr_online_nodes where | 106 | min_free_kbytes in increments of 3*pageblock_size*nr_online_nodes where |
| 107 | pageblock_size is usually the size of the default hugepage size. | 107 | pageblock_size is usually the size of the default hugepage size. |