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fs: Add Kernel-level VFS Performance Profiler
This adds a kernel-level performance profiler for the VFS. By enabling CONFIG_FS_PROFILER, the core VFS system calls (file_read, file_write, file_open, and file_close) are instrumented to track high-resolution execution times using clock_systime_timespec() seamlessly. The collected statistics are exposed dynamically via a new procfs node at /proc/fs/profile, allowing CI regression testing without needing external debugging tools. Signed-off-by: Sumit6307 <sumitkesar6307@gmail.com>
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‎Documentation/components/filesystem/index.rst‎

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@@ -543,6 +543,7 @@ NuttX provides support for a variety of file systems out of the box.
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nxffs.rst
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partition.rst
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procfs.rst
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profiler.rst
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romfs.rst
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rpmsgfs.rst
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smartfs.rst

‎Documentation/components/filesystem/profiler.rst‎

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==============================
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VFS Performance Profiler
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==============================
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The Virtual File System (VFS) Performance Profiler provides a simple, in-kernel
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mechanism to track execution times and invocation counts for core VFS operations
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(read, write, open, close) seamlessly. This is highly suitable for
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CI/CD automated regression testing and performance bottleneck identification.
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Configuration
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=============
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To enable the profiler, select ``CONFIG_FS_PROFILER`` in your Kconfig.
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To expose the metrics dynamically via procfs, ensure ``CONFIG_FS_PROCFS`` is enabled, and
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the profiler node is included via ``CONFIG_FS_PROCFS_PROFILER``.
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Usage
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=====
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When enabled, the profiler automatically intercepts calls to the underlying
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inode operations and records the execution elapsed times using ``perf_gettime()``.
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Since no blocking mutexes are used during updates (fast ``atomic.h`` operations
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are utilized instead), the overhead is extremely minimal and safely scales on SMP.
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To view the current statistics collectively from the NuttShell (NSH), simply
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read the node:
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.. code-block:: bash
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nsh> cat /proc/fs/profile
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VFS Performance Profile:
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Reads: 12 (Total time: 4500120 ns)
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Writes: 3 (Total time: 95050 ns)
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Opens: 15 (Total time: 1005000 ns)
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Closes: 15 (Total time: 45000 ns)
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The reported times are in the raw ticks/units provided by ``perf_gettime()`` on
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your specific architecture.

‎boards/sim/sim/sim/configs/citest/defconfig‎

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@@ -55,6 +55,8 @@ CONFIG_FS_FAT=y
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CONFIG_FS_HOSTFS=y
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CONFIG_FS_NAMED_SEMAPHORES=y
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CONFIG_FS_PROCFS=y
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CONFIG_FS_PROCFS_PROFILER=y
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CONFIG_FS_PROFILER=y
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CONFIG_FS_RAMMAP=y
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CONFIG_FS_ROMFS=y
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CONFIG_FS_SHMFS=y

‎commit_msg.txt‎

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fs: Add Kernel-level VFS Performance Profiler
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This adds a kernel-level performance profiler for the VFS.
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By enabling CONFIG_FS_PROFILER, the core VFS system calls
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(file_read, file_write, file_open, and file_close) are
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instrumented to track high-resolution execution times using
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clock_systime_timespec() seamlessly.
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The collected statistics are exposed dynamically via a new
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procfs node at /proc/fs/profile, allowing CI regression
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testing without needing external debugging tools.

‎fs/Kconfig‎

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comment "File system configuration"
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config FS_PROFILER
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bool "VFS Performance Profiler"
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default n
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---help---
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Enable nanosecond/microsecond-level profiling for the Virtual File
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System (VFS) operations (open, close, read, write). The profile stats
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can be read via /proc/fs/profile if PROCFS is enabled.
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config DISABLE_MOUNTPOINT
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bool "Disable support for mount points"
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default n

‎fs/procfs/CMakeLists.txt‎

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list(APPEND SRCS fs_procfspressure.c)
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endif()
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if(CONFIG_FS_PROCFS_PROFILER)
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list(APPEND SRCS fs_procfsprofile.c)
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endif()
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target_sources(fs PRIVATE ${SRCS})
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endif()

‎fs/procfs/Kconfig‎

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bool "Exclude version"
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default DEFAULT_SMALL
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config FS_PROCFS_PROFILER
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bool "Include fs/profile information"
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depends on FS_PROFILER && !DEFAULT_SMALL
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default n
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---help---
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Enable the VFS performance profiler procfs node at /proc/fs/profile.
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This node provides real-time dynamic statistics (call counts, elapsed
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time) for core VFS operations (read, write, open, close) to help
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identify filesystem performance bottlenecks and regressions.
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config FS_PROCFS_INCLUDE_PRESSURE
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bool "Include memory pressure notification"
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default n

‎fs/procfs/Make.defs‎

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CSRCS += fs_procfspressure.c
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endif
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ifeq ($(CONFIG_FS_PROCFS_PROFILER),y)
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CSRCS += fs_procfsprofile.c
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endif
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# Include procfs build support
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DEPPATH += --dep-path procfs

‎fs/procfs/fs_procfs.c‎

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extern const struct procfs_operations g_uptime_operations;
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extern const struct procfs_operations g_version_operations;
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extern const struct procfs_operations g_pressure_operations;
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#if defined(CONFIG_FS_PROFILER) && defined(CONFIG_FS_PROCFS_PROFILER)
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extern const struct procfs_operations g_fsprofile_operations;
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#endif
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/* This is not good. These are implemented in other sub-systems. Having to
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* deal with them here is not a good coupling. What is really needed is a
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#ifndef CONFIG_FS_PROCFS_EXCLUDE_VERSION
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{ "version", &g_version_operations, PROCFS_FILE_TYPE },
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#endif
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#if defined(CONFIG_FS_PROFILER) && defined(CONFIG_FS_PROCFS_PROFILER)
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{ "profile", &g_fsprofile_operations, PROCFS_FILE_TYPE },
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#endif
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};
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#ifdef CONFIG_FS_PROCFS_REGISTER

‎fs/procfs/fs_procfsprofile.c‎

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/****************************************************************************
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* fs/procfs/fs_procfsprofile.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#if defined(CONFIG_FS_PROCFS) && defined(CONFIG_FS_PROFILER) && \
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defined(CONFIG_FS_PROCFS_PROFILER)
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <stdio.h>
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#include <string.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/fs/procfs.h>
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#include "../vfs/vfs.h"
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static int profile_open(FAR struct file *filep, FAR const char *relpath,
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int oflags, mode_t mode)
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{
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return OK;
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}
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static int profile_close(FAR struct file *filep)
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{
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return OK;
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}
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static ssize_t profile_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen)
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{
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char buf[256];
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size_t linesize;
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procfs_snprintf(buf, sizeof(buf),
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"FS Performance Profile:\n"
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" Reads: %10lu (Total time: %llu ns)\n"
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" Writes: %10lu (Total time: %llu ns)\n"
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" Opens: %10lu (Total time: %llu ns)\n"
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" Closes: %10lu (Total time: %llu ns)\n",
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(unsigned long)atomic_read(&g_fs_profile.reads),
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(unsigned long long)
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atomic64_read(&g_fs_profile.total_read_time),
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(unsigned long)atomic_read(&g_fs_profile.writes),
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(unsigned long long)
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atomic64_read(&g_fs_profile.total_write_time),
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(unsigned long)atomic_read(&g_fs_profile.opens),
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(unsigned long long)
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atomic64_read(&g_fs_profile.total_open_time),
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(unsigned long)atomic_read(&g_fs_profile.closes),
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(unsigned long long)
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atomic64_read(&g_fs_profile.total_close_time));
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linesize = strlen(buf);
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return procfs_memcpy(filep, buffer, buflen, buf, linesize);
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}
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static int profile_dup(FAR const struct file *oldp, FAR struct file *newp)
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{
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return OK;
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}
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static int profile_stat(FAR const char *relpath, FAR struct stat *buf)
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{
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memset(buf, 0, sizeof(struct stat));
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buf->st_mode = S_IFREG | S_IROTH | S_IRGRP | S_IRUSR;
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return OK;
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}
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/****************************************************************************
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* Public Data
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****************************************************************************/
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const struct procfs_operations g_fsprofile_operations =
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{
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profile_open, /* open */
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profile_close, /* close */
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profile_read, /* read */
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NULL, /* write */
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NULL, /* poll */
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profile_dup, /* dup */
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NULL, /* opendir */
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NULL, /* closedir */
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NULL, /* readdir */
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NULL, /* rewinddir */
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profile_stat /* stat */
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};
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#endif
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