[RFC/PATCHSET 0/6] perf kmem: Implement page allocation analysis (v1)

Namhyung Kim
2015-03-12T07:38:36Z

Hello,

Currently perf kmem command only analyzes SLAB memory allocation. And
I'd like to introduce page allocation analysis also. Users can use
--slab and/or --page option to select it. If none of these options
are used, it does slab allocation analysis for backward compatibility.

The patch 1-3 are bugfix and cleanups. Patch 4 implements basic
support for page allocation analysis, patch 5 deals with the callsite
and finally patch 6 implements sorting.

In this patchset, I used two kmem events: kmem:mm_page_alloc and
kmem_page_free for analysis as they can track every memory
allocation/free path AFAIK. However, unlike slab tracepoint events,
those page allocation events don't provide callsite info directly. So
I recorded callchains and extracted callsites like below:

Normal page allocation callchains look like this:

360a7e __alloc_pages_nodemask
3a711c alloc_pages_current
357bc7 __page_cache_alloc <-- callsite
357cf6 pagecache_get_page
48b0a prepare_pages
494d3 __btrfs_buffered_write
49cdf btrfs_file_write_iter
3ceb6e new_sync_write
3cf447 vfs_write
3cff99 sys_write
7556e9 system_call
f880 __write_nocancel
33eb9 cmd_record
4b38e cmd_kmem
7aa23 run_builtin
27a9a main
20800 __libc_start_main

But first two are internal page allocation functions so it should be
skipped. To determine such allocation functions, I used following regex:

^_?_?(alloc|get_free|get_zeroed)_pages?

This gave me a following list of functions (you can see this with -v):

alloc func: __get_free_pages
alloc func: get_zeroed_page
alloc func: alloc_pages_exact
alloc func: __alloc_pages_direct_compact
alloc func: __alloc_pages_nodemask
alloc func: alloc_page_interleave
alloc func: alloc_pages_current
alloc func: alloc_pages_vma
alloc func: alloc_page_buffers
alloc func: alloc_pages_exact_nid

After skipping those function, it got '__page_cache_alloc'.

Other information such as allocation order, migration type and gfp
flags are provided by tracepoint events.

Basically the output will be sorted by total allocation bytes, but you
can change it by using -s/--sort option. The following sort keys are
added to support page analysis: page, order, mtype, gfp. Existing
'callsite', 'bytes' and 'hit' sort keys also can be used.

An example follows:

# perf kmem record --slab --page sleep 1
[ perf record: Woken up 0 times to write data ]
[ perf record: Captured and wrote 49.277 MB perf.data (191027 samples) ]

# perf kmem stat --page --caller -l 10 -s order,hit

--------------------------------------------------------------------------------------------
Total_alloc/Per | Hit | Order | Migrate type | GFP flag | Callsite
--------------------------------------------------------------------------------------------
65536/16384 | 4 | 2 | RECLAIMABLE | 00285250 | new_slab
51347456/4096 | 12536 | 0 | MOVABLE | 0102005a | __page_cache_alloc
53248/4096 | 13 | 0 | UNMOVABLE | 002084d0 | pte_alloc_one
40960/4096 | 10 | 0 | MOVABLE | 000280da | handle_mm_fault
28672/4096 | 7 | 0 | UNMOVABLE | 000000d0 | __pollwait
20480/4096 | 5 | 0 | MOVABLE | 000200da | do_wp_page
20480/4096 | 5 | 0 | MOVABLE | 000200da | do_cow_fault
16384/4096 | 4 | 0 | UNMOVABLE | 00000200 | __tlb_remove_page
16384/4096 | 4 | 0 | UNMOVABLE | 000084d0 | __pmd_alloc
8192/4096 | 2 | 0 | UNMOVABLE | 000084d0 | __pud_alloc
... | ... | ... | ... | ... | ...
--------------------------------------------------------------------------------------------

SUMMARY (page allocator)
========================
Total alloc requested: 12593
Total alloc failure : 0
Total bytes allocated: 51630080
Total free requested: 115
Total free unmatched: 67
Total bytes freed : 471040

Order UNMOVABLE RECLAIMABLE MOVABLE RESERVED CMA/ISOLATE
----- ------------ ------------ ------------ ------------ ------------
0 32 0 12557 0 0
1 0 0 0 0 0
2 0 4 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
5 0 0 0 0 0
6 0 0 0 0 0
7 0 0 0 0 0
8 0 0 0 0 0
9 0 0 0 0 0
10 0 0 0 0 0

I have some idea how to improve it. But I'd also like to hear other
idea, suggestion, feedback and so on.

This is available at perf/kmem-page-v1 branch on my tree:

git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git

Thanks,
Namhyung

Namhyung Kim (6):
perf kmem: Fix segfault when invalid sort key is given
perf kmem: Allow -v option
perf kmem: Fix alignment of slab result table
perf kmem: Analyze page allocator events also
perf kmem: Implement stat --page --caller
perf kmem: Support sort keys on page analysis

tools/perf/Documentation/perf-kmem.txt | 18 +-
tools/perf/builtin-kmem.c | 961 ++++++++++++++++++++++++++++++---
2 files changed, 915 insertions(+), 64 deletions(-)

--
2.3.1