v 14.6

zen/process_priority.cpp

@@ -0,0 +1,124 @@
+// *****************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under    *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
+// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
+// *****************************************************************************
+
+#include "process_priority.h"
+
+    #include <sys/resource.h> //setpriority
+
+using namespace zen;
+
+
+namespace
+{
+#if 0
+//https://linux.die.net/man/2/getpriority
+//CPU priority from highest to lowest range: [-NZERO, NZERO -1]  usually: [-20, 19]
+enum //with values from CentOS 7
+{
+    CPU_PRIO_VERYHIGH = -NZERO,
+    CPU_PRIO_HIGH     = -5,
+    CPU_PRIO_NORMAL   = 0,
+    CPU_PRIO_LOW      = 5,
+    CPU_PRIO_VERYLOW  = NZERO - 1,
+};
+
+int getCpuPriority() //throw SysError
+{
+    errno = 0;
+    const int prio = getpriority(PRIO_PROCESS, 0 /* = the calling process */);
+    if (prio == -1 && errno != 0) //"can legitimately return the value -1"
+        THROW_LAST_SYS_ERROR("getpriority");
+    return prio;
+}
+
+
+//lowering is allowed, but increasing CPU prio requires admin rights >:(
+void setCpuPriority(int prio) //throw SysError
+{
+    if (setpriority(PRIO_PROCESS, 0 /* = the calling process */, prio) != 0)
+        THROW_LAST_SYS_ERROR("setpriority(" + numberTo<std::string>(prio) + ')');
+}
+#endif
+//---------------------------------------------------------------------------------------------------
+
+//- required functions ioprio_get/ioprio_set are not part of glibc: https://linux.die.net/man/2/ioprio_set
+//- and probably never will: https://sourceware.org/bugzilla/show_bug.cgi?id=4464
+//https://github.com/torvalds/linux/blob/master/include/uapi/linux/ioprio.h
+#define IOPRIO_CLASS_SHIFT  13
+
+#define IOPRIO_PRIO_VALUE(prioclass, priolevel)         \
+    (((prioclass) << IOPRIO_CLASS_SHIFT) | (priolevel))
+
+#define IOPRIO_NORM 4
+
+enum
+{
+    IOPRIO_WHO_PROCESS = 1,
+    IOPRIO_WHO_PGRP,
+    IOPRIO_WHO_USER,
+};
+
+enum
+{
+    IOPRIO_CLASS_NONE = 0,
+    IOPRIO_CLASS_RT   = 1,
+    IOPRIO_CLASS_BE   = 2,
+    IOPRIO_CLASS_IDLE = 3,
+};
+
+
+int getIoPriority() //throw SysError
+{
+    const int rv = ::syscall(SYS_ioprio_get, IOPRIO_WHO_PROCESS, ::getpid());
+    if (rv == -1)
+        THROW_LAST_SYS_ERROR("ioprio_get");
+
+    //fix Linux kernel fuck up: bogus system default value
+    if (rv == IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM))
+        return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
+
+    return rv;
+}
+
+
+void setIoPriority(int ioPrio) //throw SysError
+{
+    if (::syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, ::getpid(), ioPrio) != 0)
+        THROW_LAST_SYS_ERROR("ioprio_set(0x" + printNumber<std::string>("%x", static_cast<unsigned int>(ioPrio)) + ')');
+}
+}
+
+
+struct SetProcessPriority::Impl
+{
+    std::optional<int> oldIoPrio;
+};
+
+
+SetProcessPriority::SetProcessPriority(ProcessPriority prio) : //throw FileError
+    pimpl_(new Impl)
+{
+    if (prio == ProcessPriority::background)
+        try
+        {
+            pimpl_->oldIoPrio = getIoPriority(); //throw SysError
+
+            setIoPriority(IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 6 /*0 (highest) to 7 (lowest)*/)); //throw SysError
+            //maybe even IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)  ? nope: "only served when no one else is using the disk"
+        }
+        catch (const SysError& e) { throw FileError(_("Cannot change process I/O priorities."), e.toString()); }
+}
+
+
+SetProcessPriority::~SetProcessPriority()
+{
+    if (pimpl_->oldIoPrio)
+        try
+        {
+            setIoPriority(*pimpl_->oldIoPrio); //throw SysError
+        }
+        catch (const SysError& e) { logExtraError(_("Cannot change process I/O priorities.") + L"\n\n" + e.toString()); }
+}