From patchwork Thu Dec 28 20:35:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13506203 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A814F10945 for ; Thu, 28 Dec 2023 20:36:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C58DC433B8; Thu, 28 Dec 2023 20:36:26 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rIx7z-00000000Dtg-49nz; Thu, 28 Dec 2023 15:37:15 -0500 From: Steven Rostedt To: linux-trace-devel@vger.kernel.org Cc: "Steven Rostedt (Google)" Subject: [PATCH 18/23] libtracefs: Add tracefs_instance_set/get_subbuf_size() Date: Thu, 28 Dec 2023 15:35:40 -0500 Message-ID: <20231228203714.53294-19-rostedt@goodmis.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231228203714.53294-1-rostedt@goodmis.org> References: <20231228203714.53294-1-rostedt@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" Add API to retrieve and modify the current sub-buffer size. tracefs_instance_set_subbuf_size() tracefs_instance_get_subbuf_size() Signed-off-by: Steven Rostedt (Google) --- Documentation/libtracefs-instances-subbuf.txt | 152 ++++++++++++++++++ Documentation/libtracefs.txt | 4 + include/tracefs.h | 2 + samples/Makefile | 1 + src/tracefs-instance.c | 37 +++++ 5 files changed, 196 insertions(+) create mode 100644 Documentation/libtracefs-instances-subbuf.txt diff --git a/Documentation/libtracefs-instances-subbuf.txt b/Documentation/libtracefs-instances-subbuf.txt new file mode 100644 index 000000000000..8d5c3e0ed3bd --- /dev/null +++ b/Documentation/libtracefs-instances-subbuf.txt @@ -0,0 +1,152 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_instance_get_subbuf_size, tracefs_instance_set_subbuf_size - Helper functions for working with ring buffer sub buffers. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +size_t *tracefs_instance_get_subbuf_size*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_instance_set_subbuf_size*(struct tracefs_instance pass:[*]_instance_, size_t _size_); +-- + +DESCRIPTION +----------- +Helper functions for working with the sub-buffers of the tracing ring buffer. +The tracing ring buffer is broken up into *sub-buffers*. An event can not be +bigger than the data section of the sub-buffer (see *tep_get_sub_buffer_data_size*(3)). +By default, the ring buffer uses the architectures *page_size* as the default +size of the sub-buffer, but this can be limiting if there is a need for large +events, for example, the application wants to write large strings into +the trace_marker file. + +The *tracefs_instance_get_subbuf_size()* returns the current size in kilobytes +fo the ring buffer sub-buffers. + +The *tracefs_instance_set_subbuf_size()* will write the size in kilobytes of +what the new sub-buffer size should be. Note, that this is only a hint to what +the minimum sub-buffer size should be. It also does not take into account the +meta-data that is used by the sub-buffer, so the size written should be no less +than 16 bytes more than the maximum event size that will be used. The kernel +will likely make the sub-buffer size larger than specified, as it may need to +align the size for implementation purposes. + +RETURN VALUE +------------ +The *tracefs_instance_get_subbuf_size()* returns the size of the current +sub-buffer for the given _instance_ ring buffer or -1 on error. + +The *tracefs_instance_set_subbuf_size()* will return 0 if it successfully set +the _instance_ ring buffer sub-buffer size in kilobytes, or -1 on error. + +EXAMPLE +------- +[source,c] +-- +#include +#include +#include + +int main(int argc, char **argv) +{ + struct tep_handle *tep; + ssize_t save_subsize; + ssize_t subsize; + char *trace; + char buf[3000]; + int meta_size; + int ret; + int i; + + tep = tep_alloc(); + ret = tracefs_load_headers(NULL, tep); + tep_free(tep); + + if (ret < 0) { + perror("reading headers"); + exit(-1); + } + + meta_size = tep_get_sub_buffer_size(tep) - tep_get_sub_buffer_data_size(tep); + + save_subsize = tracefs_instance_get_subbuf_size(NULL); + if (save_subsize < 0) { + printf("Changing sub-buffer size not available\n"); + exit(-1); + } + + subsize = save_subsize * 1024; + + /* Have at least 4 writes fit on a sub-buffer */ + if (subsize - meta_size < sizeof(buf) *4 ) { + subsize = ((sizeof(buf) * 4 + meta_size) + 1023) / 1024; + tracefs_instance_set_subbuf_size(NULL, subsize); + } + + for (i = 0; i < sizeof(buf) - 1; i++) { + buf[i] = '0' + i % 10; + } + buf[i] = '\0'; + + tracefs_instance_clear(NULL); + + for (i = 0; i < 4; i++) { + ret = tracefs_printf(NULL, "%s\n", buf); + if (ret < 0) + perror("write"); + } + + trace = tracefs_instance_file_read(NULL, "trace", NULL); + printf("%s\n", trace); + free(trace); + + printf("Buffer size was: %zd * 1024\n", + tracefs_instance_get_subbuf_size(NULL)); + + tracefs_instance_set_subbuf_size(NULL, save_subsize); +} +-- +FILES +----- +[verse] +-- +*tracefs.h* + Header file to include in order to have access to the library APIs. +*-ltracefs* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +*libtracefs*(3), +*libtraceevent*(3), +*trace-cmd*(1) + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +LICENSE +------- +libtracefs is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ + +COPYING +------- +Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt index 6752ed3c9b98..1962b3b34622 100644 --- a/Documentation/libtracefs.txt +++ b/Documentation/libtracefs.txt @@ -324,6 +324,10 @@ Recording of trace_pipe_raw files: struct kbuffer pass:[*]*tracefs_cpu_buffered_read_buf*(struct tracefs_cpu pass:[*]_tcpu_, bool _nonblock_); struct kbuffer pass:[*]*tracefs_cpu_flush_buf*(struct tracefs_cpu pass:[*]_tcpu_); +Helper functions for modifying the ring buffer sub-buffers: + size_t *tracefs_instance_get_subbuf_size*(struct tracefs_instance pass:[*]_instance_); + int *tracefs_instance_set_subbuf_size*(struct tracefs_instance pass:[*]_instance_, size_t _size_); + Helper functions for guest tracing: char pass:[*]*tracefs_find_cid_pid*(int _cid_); char pass:[*]*tracefs_instance_find_cid_pid*(struct tracefs_instance pass:[*]_instance_, int _cid_); diff --git a/include/tracefs.h b/include/tracefs.h index 3ae78d4f3af7..c66bfd2edf0b 100644 --- a/include/tracefs.h +++ b/include/tracefs.h @@ -63,6 +63,8 @@ int tracefs_instance_get_affinity_set(struct tracefs_instance *instance, cpu_set_t *set, size_t set_size); ssize_t tracefs_instance_get_buffer_size(struct tracefs_instance *instance, int cpu); int tracefs_instance_set_buffer_size(struct tracefs_instance *instance, size_t size, int cpu); +ssize_t tracefs_instance_get_subbuf_size(struct tracefs_instance *instance); +int tracefs_instance_set_subbuf_size(struct tracefs_instance *instance, size_t size); char **tracefs_instances(const char *regex); int tracefs_instance_get_buffer_percent(struct tracefs_instance *instance); diff --git a/samples/Makefile b/samples/Makefile index 787d28769051..77739c8b0aa7 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -25,6 +25,7 @@ EXAMPLES += cpu EXAMPLES += guest EXAMPLES += cpu-buf EXAMPLES += instances-stat +EXAMPLES += instances-subbuf TARGETS := TARGETS += sqlhist diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c index 2162424ad3a7..8d9dd0e21498 100644 --- a/src/tracefs-instance.c +++ b/src/tracefs-instance.c @@ -441,6 +441,43 @@ int tracefs_instance_set_buffer_size(struct tracefs_instance *instance, size_t s return ret < 0 ? -1 : 0; } +/** + * tracefs_instance_get_subbuf_size - return the sub-buffer size of the ring buffer + * @instance: The instance to get the buffer size from + * + * Returns the sub-buffer size in kilobytes. + * Returns -1 on error. + */ +ssize_t tracefs_instance_get_subbuf_size(struct tracefs_instance *instance) +{ + long long size; + int ret; + + ret = tracefs_instance_file_read_number(instance, "buffer_subbuf_size_kb", &size); + if (ret < 0) + return ret; + + return size; +} + +/** + * tracefs_instance_set_buffer_size - modify the ring buffer sub-buffer size + * @instance: The instance to modify (NULL for the top level) + * @size: The size in kilobytes to to set the sub-buffer size to + * + * Sets the sub-buffer size in kilobytes for the given ring buffer. + * + * Returns 0 on success and -1 on error. + */ +int tracefs_instance_set_subbuf_size(struct tracefs_instance *instance, size_t size) +{ + int ret; + + ret = tracefs_instance_file_write_number(instance, "buffer_subbuf_size_kb", size); + + return ret < 0 ? -1 : 0; +} + /** * tracefs_instance_get_trace_dir - return the top trace directory, where the instance is confuigred * @instance: ftrace instance