79d9333b85
Currently it discards a lock_stat for a lock instance when there's a
broken lock_seq_stat in a single task for the lock. But it also means
that the existing (and later) valid lock stat info for that lock will
be discarded as well.
This is not ideal since we can lose many valuable info because of a
single failure. Actually those failures are indepent to the existing
stat. So we can only discard the broken lock_seq_stat but keep the
valid lock_stat.
The discarded lock_seq_stat will be reallocated in a subsequent event
with SEQ_STATE_UNINITIALIZED which will be ignored until it see the
start of the next sequence. So it should be ok just free it.
Before:
$ perf lock report -F acquired,contended,avg_wait
Warning:
Processed 1401603 events and lost 18 chunks!
Check IO/CPU overload!
Name acquired contended avg wait (ns)
rcu_read_lock 251225 0 0
&(ei->i_block_re... 8731 0 0
&sb->s_type->i_l... 8731 0 0
hrtimer_bases.lock 5261 0 0
hrtimer_bases.lock 2626 0 0
hrtimer_bases.lock 1953 0 0
hrtimer_bases.lock 1382 0 0
cpu_hotplug_lock 1350 0 0
hrtimer_bases.lock 1273 0 0
hrtimer_bases.lock 1269 0 0
hrtimer_bases.lock 1198 0 0
...
New:
Name acquired contended avg wait (ns)
rcu_read_lock 251225 0 0
tk_core.seq.seqc... 54074 0 0
&xa->xa_lock 17470 0 0
&ei->i_es_lock 17464 0 0
&ei->i_raw_lock 9391 0 0
&mapping->privat... 8734 0 0
&ei->i_data_sem 8731 0 0
&(ei->i_block_re... 8731 0 0
&sb->s_type->i_l... 8731 0 0
jiffies_seq.seqc... 6953 0 0
&mm->mmap_lock 6889 0 0
balancing 5768 0 0
hrtimer_bases.lock 5261 0 0
...
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220521010811.932703-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.
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.