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Arnaldo Carvalho de Melo
5067a8cdd4
Allow stopping tracing after a number of events take place, considering
strace-like syscalls formatting as one event per enter/exit pair or when
in a multi-process tracing session a syscall is interrupted and printed
ending with '...'.
Examples included in the documentation:
Trace the first 4 open, openat or open_by_handle_at syscalls (in the future more syscalls may match here):
$ perf trace -e open* --max-events 4
[root@jouet perf]# trace -e open* --max-events 4
2272.992 ( 0.037 ms): gnome-shell/1370 openat(dfd: CWD, filename: /proc/self/stat) = 31
2277.481 ( 0.139 ms): gnome-shell/3039 openat(dfd: CWD, filename: /proc/self/stat) = 65
3026.398 ( 0.076 ms): gnome-shell/3039 openat(dfd: CWD, filename: /proc/self/stat) = 65
4294.665 ( 0.015 ms): sed/15879 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC) = 3
$
Trace the first minor page fault when running a workload:
# perf trace -F min --max-stack=7 --max-events 1 sleep 1
0.000 ( 0.000 ms): sleep/18006 minfault [__clear_user+0x1a] => 0x5626efa56080 (?k)
__clear_user ([kernel.kallsyms])
load_elf_binary ([kernel.kallsyms])
search_binary_handler ([kernel.kallsyms])
__do_execve_file.isra.33 ([kernel.kallsyms])
__x64_sys_execve ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
#
Trace the next min page page fault to take place on the first CPU:
# perf trace -F min --call-graph=dwarf --max-events 1 --cpu 0
0.000 ( 0.000 ms): Web Content/17136 minfault [js::gc::Chunk::fetchNextDecommittedArena+0x4b] => 0x7fbe6181b000 (?.)
js::gc::FreeSpan::initAsEmpty (inlined)
js::gc::Arena::setAsNotAllocated (inlined)
js::gc::Chunk::fetchNextDecommittedArena (/usr/lib64/firefox/libxul.so)
js::gc::Chunk::allocateArena (/usr/lib64/firefox/libxul.so)
js::gc::GCRuntime::allocateArena (/usr/lib64/firefox/libxul.so)
js::gc::ArenaLists::allocateFromArena (/usr/lib64/firefox/libxul.so)
js::gc::GCRuntime::tryNewTenuredThing<JSString, (js::AllowGC)1> (inlined)
js::AllocateString<JSString, (js::AllowGC)1> (/usr/lib64/firefox/libxul.so)
js::Allocate<JSThinInlineString, (js::AllowGC)1> (inlined)
JSThinInlineString::new_<(js::AllowGC)1> (inlined)
AllocateInlineString<(js::AllowGC)1, unsigned char> (inlined)
js::ConcatStrings<(js::AllowGC)1> (/usr/lib64/firefox/libxul.so)
[0x18b26e6bc2bd] (/tmp/perf-17136.map)
Tracing the next four ext4 operations on a specific CPU:
# perf trace -e ext4:*/call-graph=fp/ --max-events 4 --cpu 3
0.000 mutt/3849 ext4:ext4_es_lookup_extent_enter:dev 253,2 ino 57277 lblk 0
ext4_es_lookup_extent ([kernel.kallsyms])
read (/usr/lib64/libc-2.26.so)
0.097 mutt/3849 ext4:ext4_es_lookup_extent_exit:dev 253,2 ino 57277 found 0 [0/0) 0
ext4_es_lookup_extent ([kernel.kallsyms])
read (/usr/lib64/libc-2.26.so)
0.141 mutt/3849 ext4:ext4_ext_map_blocks_enter:dev 253,2 ino 57277 lblk 0 len 1 flags
ext4_ext_map_blocks ([kernel.kallsyms])
read (/usr/lib64/libc-2.26.so)
0.184 mutt/3849 ext4:ext4_ext_load_extent:dev 253,2 ino 57277 lblk 1516511 pblk 18446744071750013657
__read_extent_tree_block ([kernel.kallsyms])
__read_extent_tree_block ([kernel.kallsyms])
ext4_find_extent ([kernel.kallsyms])
ext4_ext_map_blocks ([kernel.kallsyms])
ext4_map_blocks ([kernel.kallsyms])
ext4_mpage_readpages ([kernel.kallsyms])
read_pages ([kernel.kallsyms])
__do_page_cache_readahead ([kernel.kallsyms])
ondemand_readahead ([kernel.kallsyms])
generic_file_read_iter ([kernel.kallsyms])
__vfs_read ([kernel.kallsyms])
vfs_read ([kernel.kallsyms])
ksys_read ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
read (/usr/lib64/libc-2.26.so)
#
Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Milian Wolff <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Rudá Moura <[email protected]>
Cc: Wang Nan <[email protected]>
Link: https://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.