From: Jeff Xie <xiehuan09@gmail.com>
To: rostedt@goodmis.org
Cc: mhiramat@kernel.org, mingo@redhat.com, zanussi@kernel.org,
linux-kernel@vger.kernel.org, Jeff Xie <xiehuan09@gmail.com>
Subject: [RFC][PATCH v5 4/4] trace/objtrace: Add documentation for objtrace trigger
Date: Sat, 13 Nov 2021 20:06:32 +0800 [thread overview]
Message-ID: <20211113120632.94754-4-xiehuan09@gmail.com> (raw)
In-Reply-To: <20211113120632.94754-1-xiehuan09@gmail.com>
Signed-off-by: Jeff Xie <xiehuan09@gmail.com>
---
Documentation/trace/events.rst | 114 +++++++++++++++++++++++++++++++++
1 file changed, 114 insertions(+)
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index 8ddb9b09451c..d1ccb9ac5e7c 100644
--- a/Documentation/trace/events.rst
+++ b/Documentation/trace/events.rst
@@ -527,6 +527,120 @@ The following commands are supported:
See Documentation/trace/histogram.rst for details and examples.
+- objtrace
+
+ This command provides a way to get the value of any object, The object
+ can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
+ static event(tracepoint).
+
+ Usage:
+ When using the kprobe event, only need to set the objtrace(a new trigger),
+ we can get the value of the object. The object is from the setting of the
+ kprobe event.
+
+ For example:
+ For the function bio_add_page():
+
+ int bio_add_page(struct bio *bio, struct page *page,
+ unsigned int len, unsigned int offset)
+
+ Firstly, we can set the base of the object, thus the first string "arg1"
+ stands for the value of the first parameter of this function bio_add_gage(),
+
+ # echo 'p bio_add_page arg1=$arg1' >> ./kprobe_events
+
+ Secondly, we can get the value dynamically base the above object.
+
+ find the offset of the bi_size in struct bio:
+ $ gdb vmlinux
+ (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
+ $1 = (unsigned int *) 0x28
+
+ # echo 'objtrace:0x28(arg1):u32:1 if comm == "cat"' > ./events/kprobes/ \
+ p_bio_add_page_0/trigger
+
+ The best way to use this is that we can set the entrance event and exit
+ event, for example, the following example is to set the read_papes as
+ the entrance event, and set the blk_account_io_start as the exit event.
+
+ # cd /sys/kernel/debug/tracing/
+ # echo 0 > ./tracing_on
+ # echo 'p read_pages' >> ./kprobe_events
+ # echo 'p blk_account_io_start' >> ./kprobe_events
+ # echo 'traceon if comm == "cat"' > ./events/kprobes/p_read_pages_0/trigger
+ # echo 'traceoff if comm == "cat"' > ./events/kprobes/p_blk_account_io_start_0/trigger
+ # echo 'p bio_add_page arg1=$arg1' >> ./kprobe_events
+ # echo 'objtrace:0x28(arg1):u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
+
+ # du -sh /test.txt
+ 12.0K /test.txt
+
+ # cat /test.txt > /dev/null
+ # cat ./trace
+
+ # tracer: nop
+ #
+ # entries-in-buffer/entries-written: 50/50 #P:1
+ #
+ # _-----=> irqs-off
+ # / _----=> need-resched
+ # | / _---=> hardirq/softirq
+ # || / _--=> preempt-depth
+ # ||| / _-=> migrate-disable
+ # |||| / delay
+ # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
+ # | | | ||||| | |
+ cat-95 [000] ..... 1.412065: _raw_spin_unlock_irqrestore <-event_triggers_call object:0xffff888108af6328 value:0x0
+ cat-95 [000] ..... 1.412066: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x0
+ cat-95 [000] ..... 1.412066: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x0
+ cat-95 [000] ..... 1.412066: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412066: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412066: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412067: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x1000
+ cat-95 [000] ..... 1.412067: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x2000
+ cat-95 [000] ..... 1.412067: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x2000
+ cat-95 [000] ..... 1.412067: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x2000
+ cat-95 [000] ..... 1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x2000
+ cat-95 [000] ..... 1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x2000
+ cat-95 [000] ..... 1.412068: submit_bio <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: submit_bio_noacct <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: __submit_bio <-submit_bio_noacct object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: blk_try_enter_queue <-__submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: submit_bio_checks <-__submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: __cond_resched <-submit_bio_checks object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: rcu_all_qs <-__cond_resched object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412068: should_fail_bio <-submit_bio_checks object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: create_task_io_context <-submit_bio_checks object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: kmem_cache_alloc_node <-create_task_io_context object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: should_failslab <-kmem_cache_alloc_node object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: _raw_spin_lock <-create_task_io_context object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: blk_mq_submit_bio <-__submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: __blk_queue_split <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: bvec_split_segs <-__blk_queue_split object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412069: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: __blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: dd_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: _raw_spin_lock <-dd_bio_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: blk_mq_sched_try_merge <-dd_bio_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: elv_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: elv_rqhash_find <-elv_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: dd_request_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: elv_rb_find <-dd_request_merge object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412070: __blk_mq_alloc_request <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: dd_limit_depth <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: blk_mq_get_tag <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: __blk_mq_get_tag <-blk_mq_get_tag object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: blk_mq_rq_ctx_init.isra.0 <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: ktime_get <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: dd_prepare_request <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: blk_account_io_start <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x3000
+ cat-95 [000] ..... 1.412071: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x3000
+
7. In-kernel trace event API
============================
--
2.25.1
next prev parent reply other threads:[~2021-11-13 12:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-13 12:06 [RFC][PATCH v5 1/4] trace: Add trace any kernel object Jeff Xie
2021-11-13 12:06 ` [RFC][PATCH v5 2/4] trace/objtrace: get the value of the object Jeff Xie
2021-11-19 14:01 ` Masami Hiramatsu
2021-11-21 17:15 ` Jeff Xie
2021-11-26 13:47 ` Jeff Xie
2021-11-26 15:19 ` Masami Hiramatsu
2021-11-26 15:32 ` Jeff Xie
2021-11-13 12:06 ` [RFC][PATCH v5 3/4] trace/objtrace: Add testcases for objtrace trigger parsing Jeff Xie
2021-11-19 14:09 ` Masami Hiramatsu
2021-11-21 17:16 ` Jeff Xie
2021-11-13 12:06 ` Jeff Xie [this message]
2021-11-19 14:00 ` [RFC][PATCH v5 1/4] trace: Add trace any kernel object Masami Hiramatsu
2021-11-19 14:58 ` Jeff Xie
2021-11-21 17:13 ` Jeff Xie
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211113120632.94754-4-xiehuan09@gmail.com \
--to=xiehuan09@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=rostedt@goodmis.org \
--cc=zanussi@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).