| Message ID | 20231209175220.19867af4@gandalf.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 40fc60e36c60ba85b2974e507b67df40c94e9578 |
| Headers | show |
| Series | trace_seq: Increase the buffer size to almost two pages | expand |
On Sat, 9 Dec 2023 17:52:20 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Now that trace_marker can hold more than 1KB string, and can write as much > as the ring buffer can hold, the trace_seq is not big enough to hold > writes: > > ~# a="1234567890" > ~# cnt=4080 > ~# s="" > ~# while [ $cnt -gt 10 ]; do > ~# s="${s}${a}" > ~# cnt=$((cnt-10)) > ~# done > ~# echo $s > trace_marker > ~# cat trace > # tracer: nop > # > # entries-in-buffer/entries-written: 2/2 #P:8 > # > # _-----=> irqs-off/BH-disabled > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / _-=> migrate-disable > # |||| / delay > # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > # | | | ||||| | | > <...>-860 [002] ..... 105.543465: tracing_mark_write[LINE TOO BIG] > <...>-860 [002] ..... 105.543496: tracing_mark_write: 789012345678901234567890 > > By increasing the trace_seq buffer to almost two pages, it can now print > out the first line. > > This also subtracts the rest of the trace_seq fields from the buffer, so > that the entire trace_seq is now PAGE_SIZE aligned. Ok, but I just a bit concern about the memory consumption. Since this is very specific case, can we make it configurable later? Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thanks, > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > include/linux/trace_seq.h | 9 ++++++--- > kernel/trace/trace.c | 6 +++--- > kernel/trace/trace_seq.c | 3 --- > 3 files changed, 9 insertions(+), 9 deletions(-) > > diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h > index 3691e0e76a1a..9ec229dfddaa 100644 > --- a/include/linux/trace_seq.h > +++ b/include/linux/trace_seq.h > @@ -8,11 +8,14 @@ > > /* > * Trace sequences are used to allow a function to call several other functions > - * to create a string of data to use (up to a max of PAGE_SIZE). > + * to create a string of data to use. > */ > > +#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \ > + (sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int))) > + > struct trace_seq { > - char buffer[PAGE_SIZE]; > + char buffer[TRACE_SEQ_BUFFER_SIZE]; > struct seq_buf seq; > size_t readpos; > int full; > @@ -21,7 +24,7 @@ struct trace_seq { > static inline void > trace_seq_init(struct trace_seq *s) > { > - seq_buf_init(&s->seq, s->buffer, PAGE_SIZE); > + seq_buf_init(&s->seq, s->buffer, TRACE_SEQ_BUFFER_SIZE); > s->full = 0; > s->readpos = 0; > } > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 83393c65ec71..da837119a446 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -3753,7 +3753,7 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str, > > /* OK if part of the temp seq buffer */ > if ((addr >= (unsigned long)iter->tmp_seq.buffer) && > - (addr < (unsigned long)iter->tmp_seq.buffer + PAGE_SIZE)) > + (addr < (unsigned long)iter->tmp_seq.buffer + TRACE_SEQ_BUFFER_SIZE)) > return true; > > /* Core rodata can not be freed */ > @@ -6926,8 +6926,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, > goto out; > } > > - if (cnt >= PAGE_SIZE) > - cnt = PAGE_SIZE - 1; > + if (cnt >= TRACE_SEQ_BUFFER_SIZE) > + cnt = TRACE_SEQ_BUFFER_SIZE - 1; > > /* reset all but tr, trace, and overruns */ > trace_iterator_reset(iter); > diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c > index 7be97229ddf8..c158d65a8a88 100644 > --- a/kernel/trace/trace_seq.c > +++ b/kernel/trace/trace_seq.c > @@ -13,9 +13,6 @@ > * trace_seq_init() more than once to reset the trace_seq to start > * from scratch. > * > - * The buffer size is currently PAGE_SIZE, although it may become dynamic > - * in the future. > - * > * A write to the buffer will either succeed or fail. That is, unlike > * sprintf() there will not be a partial write (well it may write into > * the buffer but it wont update the pointers). This allows users to > -- > 2.42.0 >
On Mon, 11 Dec 2023 21:46:27 +0900 Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > > > By increasing the trace_seq buffer to almost two pages, it can now print > > out the first line. > > > > This also subtracts the rest of the trace_seq fields from the buffer, so > > that the entire trace_seq is now PAGE_SIZE aligned. > > Ok, but I just a bit concern about the memory consumption. > Since this is very specific case, can we make it configurable later? I was concerned about this too, but it looks like it's allocated and later freed in every location except for a couple of instances. One is "tracepoint_print_iter" which is used to pipe tracepoints to printk. I think we can possibly make that allocated too. The other is in ftrace_dump, which I don't think we can easily allocate that. Although, we could have it allocated at boot up if ftrace_dump_on_oops() is enabled. Another KTODO? > > Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > Thanks! -- Steve
On Mon, 11 Dec 2023 13:28:37 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > On Mon, 11 Dec 2023 21:46:27 +0900 > Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > > > > > > By increasing the trace_seq buffer to almost two pages, it can now print > > > out the first line. > > > > > > This also subtracts the rest of the trace_seq fields from the buffer, so > > > that the entire trace_seq is now PAGE_SIZE aligned. > > > > Ok, but I just a bit concern about the memory consumption. > > Since this is very specific case, can we make it configurable later? > > I was concerned about this too, but it looks like it's allocated and later > freed in every location except for a couple of instances. > > One is "tracepoint_print_iter" which is used to pipe tracepoints to printk. > I think we can possibly make that allocated too. > > The other is in ftrace_dump, which I don't think we can easily allocate > that. Although, we could have it allocated at boot up if > ftrace_dump_on_oops() is enabled. Can we reallocate it when we detect such bigger event entry in the path of trace_marker write? If any issue happens in the reallocation, we will not finish (commit) such big event in dumping buffer anyway. > > Another KTODO? Yes, I think so. Thanks, > > > > > Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > > > Thanks! > > -- Steve
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index 3691e0e76a1a..9ec229dfddaa 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -8,11 +8,14 @@ /* * Trace sequences are used to allow a function to call several other functions - * to create a string of data to use (up to a max of PAGE_SIZE). + * to create a string of data to use. */ +#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \ + (sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int))) + struct trace_seq { - char buffer[PAGE_SIZE]; + char buffer[TRACE_SEQ_BUFFER_SIZE]; struct seq_buf seq; size_t readpos; int full; @@ -21,7 +24,7 @@ struct trace_seq { static inline void trace_seq_init(struct trace_seq *s) { - seq_buf_init(&s->seq, s->buffer, PAGE_SIZE); + seq_buf_init(&s->seq, s->buffer, TRACE_SEQ_BUFFER_SIZE); s->full = 0; s->readpos = 0; } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 83393c65ec71..da837119a446 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3753,7 +3753,7 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str, /* OK if part of the temp seq buffer */ if ((addr >= (unsigned long)iter->tmp_seq.buffer) && - (addr < (unsigned long)iter->tmp_seq.buffer + PAGE_SIZE)) + (addr < (unsigned long)iter->tmp_seq.buffer + TRACE_SEQ_BUFFER_SIZE)) return true; /* Core rodata can not be freed */ @@ -6926,8 +6926,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, goto out; } - if (cnt >= PAGE_SIZE) - cnt = PAGE_SIZE - 1; + if (cnt >= TRACE_SEQ_BUFFER_SIZE) + cnt = TRACE_SEQ_BUFFER_SIZE - 1; /* reset all but tr, trace, and overruns */ trace_iterator_reset(iter); diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c index 7be97229ddf8..c158d65a8a88 100644 --- a/kernel/trace/trace_seq.c +++ b/kernel/trace/trace_seq.c @@ -13,9 +13,6 @@ * trace_seq_init() more than once to reset the trace_seq to start * from scratch. * - * The buffer size is currently PAGE_SIZE, although it may become dynamic - * in the future. - * * A write to the buffer will either succeed or fail. That is, unlike * sprintf() there will not be a partial write (well it may write into * the buffer but it wont update the pointers). This allows users to