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[184.147.143.93]) by smtp.gmail.com with ESMTPSA id i16-20020a05620a075000b0069fc13ce1e7sm978292qki.24.2022.05.05.09.16.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 May 2022 09:16:55 -0700 (PDT) Date: Thu, 5 May 2022 12:16:54 -0400 (EDT) From: John Kacur To: Daniel Bristot de Oliveira cc: Steven Rostedt , linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Wagner Subject: Re: [PATCH v2] rtla: Remove procps-ng dependency In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Apr 2022, 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. I am for removing this dependency, but I feel I have to correct your description. procps-ng is available on RHEL. The development library however is just available at boot-time, but only because no other packages depend on it. If we were to add a package that depended on it, it would then be available at runtime. I would remove any references to RHEL in your description, and just say you are reducing the dependency on this to simply building rtla. > > 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 > Cc: Steven Rostedt > Fixes: b1696371d865 ("rtla: Helper functions for rtla") > Reported-by: Daniel Wagner > Signed-off-by: Daniel Bristot de Oliveira > --- > 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 > */ > > -#include > +#include > #include > #include > #include > @@ -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; > + > + 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; > + > + /* 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 > + * 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 > >