[PATCH 0/4] mm: cma: add some debug information for CMA

[Stefan Strogin]

Hi all.

Sorry for the long delay. Here is the second attempt to add some facility
for debugging CMA (the first one was "mm: cma: add /proc/cmainfo" [1]).

This patch set is based on v3.19 and Sasha Levin's patch set
"mm: cma: debugfs access to CMA" [2].
It is also available on git:
git://github.com/stefanstrogin/cmainfo -b cmainfo-v2

We want an interface to see a list of currently allocated CMA buffers and
some useful information about them (like /proc/vmallocinfo but for physically
contiguous buffers allocated with CMA).

Here is an example use case when we need it. We want a big (megabytes)
CMA buffer to be allocated in runtime in default CMA region. If someone
already uses CMA then the big allocation can fail. If it happens then with
such an interface we could find who used CMA at the moment of failure, who
caused fragmentation (possibly ftrace also would be helpful here) and so on.

These patches add some files to debugfs when CONFIG_CMA_DEBUGFS is enabled.

/sys/kernel/debug/cma/cma-<N>/buffers contains a list of currently allocated
CMA buffers for each CMA region. Stacktrace saved at the moment of allocation
is used to see who and whence allocated each buffer [3].

cma/cma-<N>/used and cma/cma-<N>/maxchunk are added to show used size and
the biggest free chunk in each CMA region.

Also added trace events for cma_alloc() and cma_release().

Changes from "mm: cma: add /proc/cmainfo" [1]:
- Rebased on v3.19 and Sasha Levin's patch set [2].
- Moved debug code from cma.c to cma_debug.c.
- Moved cmainfo to debugfs and splited it by CMA region.
- Splited 'cmainfo' into 'buffers', 'used' and 'maxchunk'.
- Used CONFIG_CMA_DEBUGFS instead of CONFIG_CMA_DEBUG.
- Added trace events for cma_alloc() and cma_release().
- Don't use seq_files.
- A small change of debug output in cma_release().
- cma_buffer_list_del() now supports releasing chunks which ranges don't match
  allocations. E.g. we have buffer1: [0x0, 0x1], buffer2: [0x2, 0x3], then
  cma_buffer_list_del(cma, 0x1 /*or 0x0*/, 1 /*(or 2 or 3)*/) should work.
- Various small changes.


[1] https://lkml.org/lkml/2014/12/26/95

[2] https://lkml.org/lkml/2015/1/28/755

[3] E.g.
root@debian:/sys/kernel/debug/cma# cat cma-0/buffers
0x2f400000 - 0x2f417000 (92 kB), allocated by pid 1 (swapper/0)
 [<c1142c4b>] cma_alloc+0x1bb/0x200
 [<c143d28a>] dma_alloc_from_contiguous+0x3a/0x40
 [<c10079d9>] dma_generic_alloc_coherent+0x89/0x160
 [<c14456ce>] dmam_alloc_coherent+0xbe/0x100
 [<c1487312>] ahci_port_start+0xe2/0x210
 [<c146e0e0>] ata_host_start.part.28+0xc0/0x1a0
 [<c1473650>] ata_host_activate+0xd0/0x110
 [<c14881bf>] ahci_host_activate+0x3f/0x170
 [<c14854e4>] ahci_init_one+0x764/0xab0
 [<c12e415f>] pci_device_probe+0x6f/0xd0
 [<c14378a8>] driver_probe_device+0x68/0x210
 [<c1437b09>] __driver_attach+0x79/0x80
 [<c1435eef>] bus_for_each_dev+0x4f/0x80
 [<c143749e>] driver_attach+0x1e/0x20
 [<c1437197>] bus_add_driver+0x157/0x200
 [<c14381bd>] driver_register+0x5d/0xf0
<...> 
0x2f41b000 - 0x2f41c000 (4 kB), allocated by pid 1264 (NetworkManager)
 [<c1142c4b>] cma_alloc+0x1bb/0x200
 [<c143d28a>] dma_alloc_from_contiguous+0x3a/0x40
 [<c10079d9>] dma_generic_alloc_coherent+0x89/0x160
 [<c14c5d13>] e1000_setup_all_tx_resources+0x93/0x540
 [<c14c8021>] e1000_open+0x31/0x120
 [<c16264cf>] __dev_open+0x9f/0x130
 [<c16267ce>] __dev_change_flags+0x8e/0x150
 [<c16268b8>] dev_change_flags+0x28/0x60
 [<c1633ee0>] do_setlink+0x2a0/0x760
 [<c1634acb>] rtnl_newlink+0x60b/0x7b0
 [<c16314f4>] rtnetlink_rcv_msg+0x84/0x1f0
 [<c164b58e>] netlink_rcv_skb+0x8e/0xb0
 [<c1631461>] rtnetlink_rcv+0x21/0x30
 [<c164af7a>] netlink_unicast+0x13a/0x1d0
 [<c164b250>] netlink_sendmsg+0x240/0x3e0
 [<c160cbfd>] do_sock_sendmsg+0xbd/0xe0
<...>


Dmitry Safonov (1):
  mm: cma: add functions to get region pages counters

Stefan Strogin (3):
  mm: cma: add currently allocated CMA buffers list to debugfs
  mm: cma: add number of pages to debug message in cma_release()
  mm: cma: add trace events to debug physically-contiguous memory
    allocations

 include/linux/cma.h        |  11 +++
 include/trace/events/cma.h |  57 +++++++++++++++
 mm/cma.c                   |  46 +++++++++++-
 mm/cma.h                   |  16 +++++
 mm/cma_debug.c             | 169 ++++++++++++++++++++++++++++++++++++++++++++-
 5 files changed, 297 insertions(+), 2 deletions(-)
 create mode 100644 include/trace/events/cma.h

-- 
2.1.0

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