On Fri, Apr 29, 2022 at 03:01:48PM +0200,
Daniel Bristot de Oliveira wrote:
> Daniel Wagner reported to me that readproc.h got deprecated. Also,
> while the procps-ng library was available on Fedora, it was not available
> on RHEL, which is a piece of evidence that it was not that used.
>
> rtla uses procps-ng only to find the PID of the tracers' workload.
>
> I used the procps-ng library to avoid reinventing the wheel. But in this
> case, reinventing the wheel took me less time than the time we already
> took trying to work around problems.
>
> Implement a function that reads /proc/ entries, checking if:
> - the entry is a directory
> - the directory name is composed only of digits (PID)
> - the directory contains the comm file
> - the comm file contains a comm that matches the tracers'
> workload prefix.
> - then return true; otherwise, return false.
>
> And use it instead of procps-ng.
>
> Changes from V1:
> - Use a single buffer for comm and comm_path
> - Cause an error in case of a too long command prefix
> - Do a close_dir()
> - Improve log messages
>
> Cc: John Kacur <jkacur@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Fixes: b1696371d865 ("rtla: Helper functions for rtla")
> Reported-by: Daniel Wagner <dwagner@xxxxxxx>
> Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> ---
> tools/tracing/rtla/Makefile | 2 +-
> tools/tracing/rtla/README.txt | 1 -
> tools/tracing/rtla/src/utils.c | 102 ++++++++++++++++++++++++++-------
> tools/tracing/rtla/src/utils.h | 3 +-
> 4 files changed, 84 insertions(+), 24 deletions(-)
>
> diff --git a/tools/tracing/rtla/Makefile b/tools/tracing/rtla/Makefile
> index 5a3226e436ef..523f0a8c38c2 100644
> --- a/tools/tracing/rtla/Makefile
> +++ b/tools/tracing/rtla/Makefile
> @@ -32,7 +32,7 @@ TRACEFS_HEADERS := $$($(PKG_CONFIG) --cflags libtracefs)
>
> CFLAGS := -O -g -DVERSION=\"$(VERSION)\" $(FOPTS) $(MOPTS) $(WOPTS) $(TRACEFS_HEADERS)
> LDFLAGS := -ggdb
> -LIBS := $$($(PKG_CONFIG) --libs libtracefs) -lprocps
> +LIBS := $$($(PKG_CONFIG) --libs libtracefs)
>
> SRC := $(wildcard src/*.c)
> HDR := $(wildcard src/*.h)
> diff --git a/tools/tracing/rtla/README.txt b/tools/tracing/rtla/README.txt
> index 0fbad2640b8c..4af3fd40f171 100644
> --- a/tools/tracing/rtla/README.txt
> +++ b/tools/tracing/rtla/README.txt
> @@ -11,7 +11,6 @@ RTLA depends on the following libraries and tools:
>
> - libtracefs
> - libtraceevent
> - - procps
>
> It also depends on python3-docutils to compile man pages.
>
> diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
> index 3bd6f64780cf..f3d562f7f14c 100644
> --- a/tools/tracing/rtla/src/utils.c
> +++ b/tools/tracing/rtla/src/utils.c
> @@ -3,7 +3,7 @@
> * Copyright (C) 2021 Red Hat Inc, Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> */
>
> -#include <proc/readproc.h>
> +#include <dirent.h>
> #include <stdarg.h>
> #include <stdlib.h>
> #include <string.h>
> @@ -262,43 +262,103 @@ int __set_sched_attr(int pid, struct sched_attr *attr)
>
> return 0;
> }
> +
> /*
> - * set_comm_sched_attr - set sched params to threads starting with char *comm
> + * procfs_is_workload_pid - check if a procfs entry contains a comm_prefix* comm
> + *
> + * Check if the procfs entry is a directory of a process, and then check if the
> + * process has a comm with the prefix set in char *comm_prefix. As the
> + * current users of this function only check for kernel threads, there is no
> + * need to check for the threads for the process.
> *
> - * This function uses procps to list the currently running threads and then
> - * set the sched_attr *attr to the threads that start with char *comm. It is
> + * Return: True if the proc_entry contains a comm file with comm_prefix*.
> + * Otherwise returns false.
> + */
> +static int procfs_is_workload_pid(const char *comm_prefix, struct dirent *proc_entry)
> +{
> + char buffer[MAX_PATH];
> + int comm_fd, retval;
> + char*t_name;
Need a blank..
char *t_name;
> +
> + if (proc_entry->d_type != DT_DIR)
> + return 0;
> +
> + if (*proc_entry->d_name == '.')
> + return 0;
> +
> + /* check if the string is a pid */
> + for (t_name = proc_entry->d_name; t_name; t_name++) {
> + if (!isdigit(*t_name))
> + break;
> + }
> +
> + if (*t_name != '\0')
> + return 0;
> +
> + snprintf(buffer, MAX_PATH, "/proc/%s/comm", proc_entry->d_name);
> + comm_fd = open(buffer, O_RDONLY);
> + if (comm_fd < 0)
> + return 0;
> +
> + memset(buffer, 0, MAX_PATH);
> + retval = read(comm_fd, buffer, MAX_PATH);
> +
> + close(comm_fd);
> +
> + if (retval <= 0)
> + return 0;
> +
> + retval = strncmp(comm_prefix, buffer, strlen(comm_prefix));
> + if (retval)
> + return 0;
Confused.
For example:
comm_prefix is "osnoise/", buffer is "osnoise\n"(as said by comment below),
strlen_prefix is 8. The return value of strncmp() is 1 and not set sched attr.
Or use "osnoise" as the comm_prefix. Or am I miss something here.
> + /* comm already have \n */
> + debug_msg("Found workload pid:%s comm:%s", proc_entry->d_name, buffer);
> +
> + return 1;
> +}
> +
> +/*
> + * set_comm_sched_attr - set sched params to threads starting with char *comm_prefix
> + *
> + * This function uses procps to list the currently running threads and then set the
s/procps/procfs/
Thanks,
Tao
> + * sched_attr *attr to the threads that start with char *comm_prefix. It is
> * mainly used to set the priority to the kernel threads created by the
> * tracers.
> */
> -int set_comm_sched_attr(const char *comm, struct sched_attr *attr)
> +int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr)
> {
> - int flags = PROC_FILLCOM | PROC_FILLSTAT;
> - PROCTAB *ptp;
> - proc_t task;
> + struct dirent *proc_entry;
> + DIR *procfs;
> int retval;
>
> - ptp = openproc(flags);
> - if (!ptp) {
> - err_msg("error openproc()\n");
> - return -ENOENT;
> + if (strlen(comm_prefix) >= MAX_PATH) {
> + err_msg("Command prefix is too long: %d < strlen(%s)\n",
> + MAX_PATH, comm_prefix);
> + exit(EINVAL);
> }
>
> - memset(&task, 0, sizeof(task));
> + procfs = opendir("/proc");
> +
> + while ((proc_entry = readdir(procfs))) {
>
> - while (readproc(ptp, &task)) {
> - retval = strncmp(comm, task.cmd, strlen(comm));
> - if (retval)
> + retval = procfs_is_workload_pid(comm_prefix, proc_entry);
> + if (!retval)
> continue;
> - retval = __set_sched_attr(task.tid, attr);
> - if (retval)
> +
> + /* procfs_is_workload_pid confirmed it is a pid */
> + retval = __set_sched_attr(atoi(proc_entry->d_name), attr);
> + if (retval) {
> + err_msg("Error setting sched attributes for pid:%s\n", proc_entry->d_name);
> goto out_err;
> - }
> + }
>
> - closeproc(ptp);
> + debug_msg("Set sched attributes for pid:%s\n", proc_entry->d_name);
> + }
> return 0;
>
> out_err:
> - closeproc(ptp);
> + closedir(procfs);
> return 1;
> }
>
> diff --git a/tools/tracing/rtla/src/utils.h b/tools/tracing/rtla/src/utils.h
> index fa08e374870a..5571afd3b549 100644
> --- a/tools/tracing/rtla/src/utils.h
> +++ b/tools/tracing/rtla/src/utils.h
> @@ -6,6 +6,7 @@
> * '18446744073709551615\0'
> */
> #define BUFF_U64_STR_SIZE 24
> +#define MAX_PATH 1024
>
> #define container_of(ptr, type, member)({ \
> const typeof(((type *)0)->member) *__mptr = (ptr); \
> @@ -53,5 +54,5 @@ struct sched_attr {
> };
>
> int parse_prio(char *arg, struct sched_attr *sched_param);
> -int set_comm_sched_attr(const char *comm, struct sched_attr *attr);
> +int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr);
> int set_cpu_dma_latency(int32_t latency);
> --
> 2.32.0
>
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