| Message ID | 20190415164739.17223-2-kaslevs@vmware.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Optimize pid filters and add --no-filter option | expand |
On Mon, 15 Apr 2019 19:47:38 +0300 Slavomir Kaslev <kaslevs@vmware.com> wrote: > Express pid filters as allowed/disallowed filter ranges > > (pid>=100&&pid<=103) > > instead of specifying them per pid > > (pid==100||pid==101||pid==102||pid==103) > > This makes the size of the resulting filter smaller (and faster) and avoids > overflowing the filter size limit of one page which we can hit on bigger > machines (say >160 CPUs). Except it breaks if we have a split. I ran this: hackbench 10 & tracecmd/trace-cmd record -e sched_switch cat /sys/kernel/debug/tracing/events/sched/sched_switch/filter Time: 0.093 (common_pid<6959||common_pid>6969)||(common_pid<6945||common_pid>6957)||(next_pid<6959||next_pid>6969)||(next_pid<6945||next_pid>6957) This was the output. Showing that we had common_pid from 6959 - 6969 and 6945 - 6957 (a 6958 was missing), and because of this, we now trace all processes because (common_pid < 6959 || common_pid > 6957) is always true. We need an "&&" there somewhere. That should have been: ((common_pid<6959||common_pid>6969)&&(common_pid<6945||common_pid>6957))||((next_pid<6959||next_pid>6969)&&(next_pid<6945||next_pid>6957)) -- Steve > > Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com> > Reported-by: Phil Auld <pauld@redhat.com> > Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > tracecmd/trace-record.c | 115 +++++++++++++++++++++++++++------------- > 1 file changed, 78 insertions(+), 37 deletions(-) > > diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c > index 76ca92d..eeee5e9 100644 > --- a/tracecmd/trace-record.c > +++ b/tracecmd/trace-record.c > @@ -950,10 +950,61 @@ static void update_ftrace_pids(int reset) > static void update_event_filters(struct buffer_instance *instance); > static void update_pid_event_filters(struct buffer_instance *instance); > > +static void append_filter_pid_range(char **filter, int *curr_len, > + const char *field, > + int start_pid, int end_pid, bool exclude) > +{ > + char *op, *op1, *op2, *op3; > + int len; > + > + op = *filter && **filter ? "||" : ""; > + > + // Handle thus case explicitly so that we get `pid==3` instead of > + // `pid>=3&&pid<=3` for singleton ranges > + if (start_pid == end_pid) { > +#define FMT "%s(%s%s%d)" > + len = snprintf(NULL, 0, FMT, op, > + field, exclude ? "!=" : "==", start_pid); > + *filter = realloc(*filter, *curr_len + len + 1); > + if (!*filter) > + die("realloc"); > + > + len = snprintf(*filter + *curr_len, len + 1, FMT, op, > + field, exclude ? "!=" : "==", start_pid); > + *curr_len += len; > + > + return; > +#undef FMT > + } > + > + if (exclude) { > + op1 = "<"; > + op2 = "||"; > + op3 = ">"; > + } else { > + op1 = ">="; > + op2 = "&&"; > + op3 = "<="; > + } > + > +#define FMT "%s(%s%s%d%s%s%s%d)" > + len = snprintf(NULL, 0, FMT, op, > + field, op1, start_pid, op2, > + field, op3, end_pid); > + *filter = realloc(*filter, *curr_len + len + 1); > + if (!*filter) > + die("realloc"); > + > + len = snprintf(*filter + *curr_len, len + 1, FMT, op, > + field, op1, start_pid, op2, > + field, op3, end_pid); > + *curr_len += len; > +} > + > /** > * make_pid_filter - create a filter string to all pids against @field > * @curr_filter: Append to a previous filter (may realloc). Can be NULL > - * @field: The fild to compare the pids against > + * @field: The field to compare the pids against > * > * Creates a new string or appends to an existing one if @curr_filter > * is not NULL. The new string will contain a filter with all pids > @@ -963,54 +1014,44 @@ static void update_pid_event_filters(struct buffer_instance *instance); > */ > static char *make_pid_filter(char *curr_filter, const char *field) > { > + int curr_len = 0, last_exclude = -1; > + int start_pid = -1, last_pid = -1; > + char *filter = NULL, *save; > struct filter_pids *p; > - char *filter; > - char *orit; > - char *match; > - char *str; > - int curr_len = 0; > - int len; > > /* Use the new method if possible */ > if (have_set_event_pid) > return NULL; > > - len = len_filter_pids + (strlen(field) + strlen("(==)||")) * nr_filter_pids; > - > - if (curr_filter) { > - curr_len = strlen(curr_filter); > - filter = realloc(curr_filter, curr_len + len + strlen("(&&())")); > - if (!filter) > - die("realloc"); > - memmove(filter+1, curr_filter, curr_len); > - filter[0] = '('; > - strcat(filter, ")&&("); > - curr_len = strlen(filter); > - } else > - filter = malloc(len); > - if (!filter) > - die("Failed to allocate pid filter"); > - > - /* Last '||' that is not used will cover the \0 */ > - str = filter + curr_len; > + if (!filter_pids) > + return curr_filter; > > for (p = filter_pids; p; p = p->next) { > - if (p->exclude) { > - match = "!="; > - orit = "&&"; > - } else { > - match = "=="; > - orit = "||"; > + /* PIDs are inserted in `filter_pids` from the front and that's > + * why we expect them in descending order here. > + */ > + if (p->pid == last_pid - 1 && p->exclude == last_exclude) { > + last_pid = p->pid; > + continue; > } > - if (p == filter_pids) > - orit = ""; > > - len = sprintf(str, "%s(%s%s%d)", orit, field, match, p->pid); > - str += len; > + if (start_pid != -1) > + append_filter_pid_range(&filter, &curr_len, field, > + last_pid, start_pid, > + last_exclude); > + > + start_pid = last_pid = p->pid; > + last_exclude = p->exclude; > + > } > + append_filter_pid_range(&filter, &curr_len, field, > + last_pid, start_pid, last_exclude); > > - if (curr_len) > - sprintf(str, ")"); > + if (curr_filter) { > + save = filter; > + asprintf(&filter, "(%s)&&(%s)", curr_filter, filter); > + free(save); > + } > > return filter; > }
On Mon, 2019-04-15 at 17:59 -0400, Steven Rostedt wrote: > On Mon, 15 Apr 2019 19:47:38 +0300 > Slavomir Kaslev <kaslevs@vmware.com> wrote: > > > Express pid filters as allowed/disallowed filter ranges > > > > (pid>=100&&pid<=103) > > > > instead of specifying them per pid > > > > (pid==100||pid==101||pid==102||pid==103) > > > > This makes the size of the resulting filter smaller (and faster) > > and avoids > > overflowing the filter size limit of one page which we can hit on > > bigger > > machines (say >160 CPUs). > > Except it breaks if we have a split. > > I ran this: > > hackbench 10 & > tracecmd/trace-cmd record -e sched_switch cat > /sys/kernel/debug/tracing/events/sched/sched_switch/filter > > > Time: 0.093 > (common_pid<6959||common_pid>6969)||(common_pid<6945||common_pid>6957 > )||(next_pid<6959||next_pid>6969)||(next_pid<6945||next_pid>6957) > > This was the output. Showing that we had common_pid from 6959 - 6969 > and 6945 - 6957 (a 6958 was missing), and because of this, we now > trace > all processes because (common_pid < 6959 || common_pid > 6957) is > always true. > > We need an "&&" there somewhere. That should have been: > > ((common_pid<6959||common_pid>6969)&&(common_pid<6945||common_pid>695 > 7))||((next_pid<6959||next_pid>6969)&&(next_pid<6945||next_pid>6957)) Good catch. I've misread how the original code worked. It appends exclude filters with && and non-exclude with ||. I'll send a fix in v3. -- Slavi
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c index 76ca92d..eeee5e9 100644 --- a/tracecmd/trace-record.c +++ b/tracecmd/trace-record.c @@ -950,10 +950,61 @@ static void update_ftrace_pids(int reset) static void update_event_filters(struct buffer_instance *instance); static void update_pid_event_filters(struct buffer_instance *instance); +static void append_filter_pid_range(char **filter, int *curr_len, + const char *field, + int start_pid, int end_pid, bool exclude) +{ + char *op, *op1, *op2, *op3; + int len; + + op = *filter && **filter ? "||" : ""; + + // Handle thus case explicitly so that we get `pid==3` instead of + // `pid>=3&&pid<=3` for singleton ranges + if (start_pid == end_pid) { +#define FMT "%s(%s%s%d)" + len = snprintf(NULL, 0, FMT, op, + field, exclude ? "!=" : "==", start_pid); + *filter = realloc(*filter, *curr_len + len + 1); + if (!*filter) + die("realloc"); + + len = snprintf(*filter + *curr_len, len + 1, FMT, op, + field, exclude ? "!=" : "==", start_pid); + *curr_len += len; + + return; +#undef FMT + } + + if (exclude) { + op1 = "<"; + op2 = "||"; + op3 = ">"; + } else { + op1 = ">="; + op2 = "&&"; + op3 = "<="; + } + +#define FMT "%s(%s%s%d%s%s%s%d)" + len = snprintf(NULL, 0, FMT, op, + field, op1, start_pid, op2, + field, op3, end_pid); + *filter = realloc(*filter, *curr_len + len + 1); + if (!*filter) + die("realloc"); + + len = snprintf(*filter + *curr_len, len + 1, FMT, op, + field, op1, start_pid, op2, + field, op3, end_pid); + *curr_len += len; +} + /** * make_pid_filter - create a filter string to all pids against @field * @curr_filter: Append to a previous filter (may realloc). Can be NULL - * @field: The fild to compare the pids against + * @field: The field to compare the pids against * * Creates a new string or appends to an existing one if @curr_filter * is not NULL. The new string will contain a filter with all pids @@ -963,54 +1014,44 @@ static void update_pid_event_filters(struct buffer_instance *instance); */ static char *make_pid_filter(char *curr_filter, const char *field) { + int curr_len = 0, last_exclude = -1; + int start_pid = -1, last_pid = -1; + char *filter = NULL, *save; struct filter_pids *p; - char *filter; - char *orit; - char *match; - char *str; - int curr_len = 0; - int len; /* Use the new method if possible */ if (have_set_event_pid) return NULL; - len = len_filter_pids + (strlen(field) + strlen("(==)||")) * nr_filter_pids; - - if (curr_filter) { - curr_len = strlen(curr_filter); - filter = realloc(curr_filter, curr_len + len + strlen("(&&())")); - if (!filter) - die("realloc"); - memmove(filter+1, curr_filter, curr_len); - filter[0] = '('; - strcat(filter, ")&&("); - curr_len = strlen(filter); - } else - filter = malloc(len); - if (!filter) - die("Failed to allocate pid filter"); - - /* Last '||' that is not used will cover the \0 */ - str = filter + curr_len; + if (!filter_pids) + return curr_filter; for (p = filter_pids; p; p = p->next) { - if (p->exclude) { - match = "!="; - orit = "&&"; - } else { - match = "=="; - orit = "||"; + /* PIDs are inserted in `filter_pids` from the front and that's + * why we expect them in descending order here. + */ + if (p->pid == last_pid - 1 && p->exclude == last_exclude) { + last_pid = p->pid; + continue; } - if (p == filter_pids) - orit = ""; - len = sprintf(str, "%s(%s%s%d)", orit, field, match, p->pid); - str += len; + if (start_pid != -1) + append_filter_pid_range(&filter, &curr_len, field, + last_pid, start_pid, + last_exclude); + + start_pid = last_pid = p->pid; + last_exclude = p->exclude; + } + append_filter_pid_range(&filter, &curr_len, field, + last_pid, start_pid, last_exclude); - if (curr_len) - sprintf(str, ")"); + if (curr_filter) { + save = filter; + asprintf(&filter, "(%s)&&(%s)", curr_filter, filter); + free(save); + } return filter; }
Express pid filters as allowed/disallowed filter ranges (pid>=100&&pid<=103) instead of specifying them per pid (pid==100||pid==101||pid==102||pid==103) This makes the size of the resulting filter smaller (and faster) and avoids overflowing the filter size limit of one page which we can hit on bigger machines (say >160 CPUs). Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com> Reported-by: Phil Auld <pauld@redhat.com> Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> --- tracecmd/trace-record.c | 115 +++++++++++++++++++++++++++------------- 1 file changed, 78 insertions(+), 37 deletions(-)