Commit 3cdd868e authored by Changbin Du's avatar Changbin Du Committed by Jonathan Corbet

trace doc: convert trace/events-kmem.txt to rst format

This converts the plain text documentation to reStructuredText format and
add it into Sphinx TOC tree. No essential content change.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarChangbin Du <changbin.du@intel.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 73d98127
Subsystem Trace Points: kmem
============================
Subsystem Trace Points: kmem
============================
The kmem tracing system captures events related to object and page allocation
within the kernel. Broadly speaking there are five major subheadings.
o Slab allocation of small objects of unknown type (kmalloc)
o Slab allocation of small objects of known type
o Page allocation
o Per-CPU Allocator Activity
o External Fragmentation
- Slab allocation of small objects of unknown type (kmalloc)
- Slab allocation of small objects of known type
- Page allocation
- Per-CPU Allocator Activity
- External Fragmentation
This document describes what each of the tracepoints is and why they
might be useful.
1. Slab allocation of small objects of unknown type
===================================================
kmalloc call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
kmalloc_node call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
kfree call_site=%lx ptr=%p
::
kmalloc call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
kmalloc_node call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
kfree call_site=%lx ptr=%p
Heavy activity for these events may indicate that a specific cache is
justified, particularly if kmalloc slab pages are getting significantly
......@@ -27,9 +31,11 @@ the allocation sites were.
2. Slab allocation of small objects of known type
=================================================
kmem_cache_alloc call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
kmem_cache_alloc_node call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
kmem_cache_free call_site=%lx ptr=%p
::
kmem_cache_alloc call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
kmem_cache_alloc_node call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
kmem_cache_free call_site=%lx ptr=%p
These events are similar in usage to the kmalloc-related events except that
it is likely easier to pin the event down to a specific cache. At the time
......@@ -38,10 +44,12 @@ but the call_site can usually be used to extrapolate that information.
3. Page allocation
==================
mm_page_alloc page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s
mm_page_alloc_zone_locked page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
mm_page_free page=%p pfn=%lu order=%d
mm_page_free_batched page=%p pfn=%lu order=%d cold=%d
::
mm_page_alloc page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s
mm_page_alloc_zone_locked page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
mm_page_free page=%p pfn=%lu order=%d
mm_page_free_batched page=%p pfn=%lu order=%d cold=%d
These four events deal with page allocation and freeing. mm_page_alloc is
a simple indicator of page allocator activity. Pages may be allocated from
......@@ -65,8 +73,10 @@ contention on the zone->lru_lock.
4. Per-CPU Allocator Activity
=============================
mm_page_alloc_zone_locked page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
mm_page_pcpu_drain page=%p pfn=%lu order=%d cpu=%d migratetype=%d
::
mm_page_alloc_zone_locked page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
mm_page_pcpu_drain page=%p pfn=%lu order=%d cpu=%d migratetype=%d
In front of the page allocator is a per-cpu page allocator. It exists only
for order-0 pages, reduces contention on the zone->lock and reduces the
......@@ -92,7 +102,9 @@ can be allocated and freed on the same CPU through some algorithm change.
5. External Fragmentation
=========================
mm_page_alloc_extfrag page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d
::
mm_page_alloc_extfrag page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d
External fragmentation affects whether a high-order allocation will be
successful or not. For some types of hardware, this is important although
......
......@@ -13,3 +13,4 @@ Linux Tracing Technologies
uprobetracer
tracepoints
events
events-kmem
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