Feature: Niceness: Added new options to specify the new process priority

.gitignore

@@ -59,3 +59,11 @@ aclocal.m4
 .deps
 /*.exe
 *.dSYM/
+simdtest
+t_chmod_secure
+t_secure_relpath
+testsuite/__pycache__/
+testsuite/chown-fake_test.py
+testsuite/devices-fake_test.py
+testsuite/exclude-lsh_test.py
+testsuite/xattrs-hlink_test.py

Makefile.in

@@ -46,7 +46,7 @@ zlib_OBJS=zlib/deflate.o zlib/inffast.o zlib/inflate.o zlib/inftrees.o \
 OBJS1=flist.o rsync.o generator.o receiver.o cleanup.o sender.o exclude.o \
 	util1.o util2.o main.o checksum.o match.o syscall.o log.o backup.o delete.o
 OBJS2=options.o io.o compat.o hlink.o token.o uidlist.o socket.o hashtable.o \
-	usage.o fileio.o batch.o clientname.o chmod.o acls.o xattrs.o
+	usage.o fileio.o batch.o clientname.o chmod.o acls.o xattrs.o niceness.o
 OBJS3=progress.o pipe.o @MD5_ASM@ @ROLL_SIMD@ @ROLL_ASM@
 DAEMON_OBJ = params.o loadparm.o clientserver.o access.o connection.o authenticate.o
 popt_OBJS= popt/popt.o  popt/poptconfig.o \

configure.ac

@@ -13,7 +13,7 @@ AC_CHECK_HEADERS(sys/fcntl.h sys/select.h fcntl.h sys/time.h sys/unistd.h \
     sys/acl.h acl/libacl.h attr/xattr.h sys/xattr.h sys/extattr.h dl.h \
     popt.h popt/popt.h linux/falloc.h netinet/in_systm.h netgroup.h \
     zlib.h xxhash.h openssl/md4.h openssl/md5.h zstd.h lz4.h sys/file.h \
-    bsd/string.h)
+    bsd/string.h sys/resource.h linux/ioprio.h sys/syscall.h)
 AC_CHECK_HEADERS([netinet/ip.h], [], [], [[#include <netinet/in.h>]])
 AC_HEADER_MAJOR_FIXED
 
@@ -1465,6 +1465,8 @@ case "$CC" in
     ;;
 esac
 
+AC_DEFINE_UNQUOTED([COMPILE_TARGET], ["$host"], [String describing the compiled target OS and architecture])
+
 AC_CONFIG_FILES([Makefile lib/dummy zlib/dummy popt/dummy shconfig])
 AC_OUTPUT
 

main.c

@@ -107,6 +107,8 @@ extern char backup_dir_buf[MAXPATHLEN];
 extern char *basis_dir[MAX_BASIS_DIRS+1];
 extern struct file_list *first_flist;
 extern filter_rule_list daemon_filter_list, implied_filter_list;
+extern int nice_local;
+extern int ionice_local;
 
 uid_t our_uid;
 gid_t our_gid;
@@ -1835,6 +1837,14 @@ int main(int argc,char *argv[])
 	if (write_batch < 0)
 		dry_run = 1;
 
+	if (nice_local) {
+		renice_me(nice_local);
+	}
+
+	if (ionice_local) {
+		ionice_me();
+	}
+
 	if (am_server) {
 #ifdef ICONV_CONST
 		setup_iconv();

niceness.c

@@ -0,0 +1,70 @@
+/*
+ * Renice or ionice the current process to reduce its impact on the system
+ *
+ * Copyright (C) 2026 Michael Mess
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, visit the http://fsf.org website.
+ */
+
+#include "rsync.h"
+
+extern int am_server;
+
+int get_renice_default_prio()
+{
+	return 19; // lowest CPU Priority
+}
+
+void renice_me(int prio)
+{
+#ifdef SUPPORT_RENICE
+	int which = PRIO_PROCESS; // who specifies a Process ID
+	int who = 0; // 0 means current process
+	int result = setpriority(which, who, prio);
+	if ( result < 0 ) {
+		// Failed to set priority, inform user, but can be ignored (it's just not so nice).
+		rprintf(FWARNING, "renice to %d rejected by OS (%s version %s): %s\n",
+			prio, RSYNC_NAME, rsync_version(), strerror(errno));
+	} else {
+		if (DEBUG_GTE(CMD, 1))
+				rprintf(FINFO, "successfully reniced %s to new priority %d\n", am_server ? "server" : "client", prio);
+	}
+#else
+	rprintf(FWARNING, "renice not supported for %s (%s: %s version %s)\n",
+			COMPILE_TARGET, am_server ? "server" : "client", RSYNC_NAME, rsync_version());
+#endif
+}
+
+void ionice_me() 
+{
+#ifdef SUPPORT_IONICE
+	int which = IOPRIO_WHO_PROCESS; // who specifies a Process ID
+	int who = 0; // 0 means current process
+	int class = IOPRIO_CLASS_IDLE;
+	int data = 0; // Ignored when using the IOPRIO_CLASS_IDLE class
+	int ioprio = IOPRIO_PRIO_VALUE(class, data);
+	int result = syscall(SYS_ioprio_set, which, who, ioprio);
+	if ( result < 0 ) {
+		// Failed to set priority, inform user, but can be ignored (it's just not so ionice).
+		rprintf(FWARNING, "ionice rejected by OS (%s version %s)\n",
+			RSYNC_NAME, rsync_version());
+	} else {
+		if (DEBUG_GTE(CMD, 1))
+			rprintf(FINFO, "successfully ioniced %s\n", am_server ? "server" : "client");
+	}
+#else
+	rprintf(FWARNING, "ionice not supported for %s (%s: %s version %s)\n",
+			COMPILE_TARGET, am_server ? "server" : "client", RSYNC_NAME, rsync_version());
+#endif
+}

options.c

@@ -35,6 +35,19 @@ extern filter_rule_list daemon_filter_list;
 
 int make_backups = 0;
 
+/* If set to other than 0, be nice on the local or remote site
+ * Contains the nice priority to be set on the process, or 0=feature is turned off, no priority will be set.
+ * I have to admit, that it is not possible to set a nice value of 0 with this code,
+ * but in most cases 0 should be the priority of the newly started rsync process already anyway.
+ */
+int nice_local = 0;
+int nice_remote = 0;
+/* If set to other than 0, be ionice on the local or remote site
+ * Currently only idle is supported for ionice when turned on.
+ */
+int ionice_local = 0;
+int ionice_remote = 0;
+
 /**
  * If 1, send the whole file as literal data rather than trying to
  * create an incremental diff.
@@ -594,7 +607,8 @@ enum {OPT_SERVER = 1000, OPT_DAEMON, OPT_SENDER, OPT_EXCLUDE, OPT_EXCLUDE_FROM,
       OPT_NO_D, OPT_APPEND, OPT_NO_ICONV, OPT_INFO, OPT_DEBUG, OPT_BLOCK_SIZE,
       OPT_USERMAP, OPT_GROUPMAP, OPT_CHOWN, OPT_BWLIMIT, OPT_STDERR,
       OPT_OLD_COMPRESS, OPT_NEW_COMPRESS, OPT_NO_COMPRESS, OPT_OLD_ARGS,
-      OPT_STOP_AFTER, OPT_STOP_AT,
+      OPT_STOP_AFTER, OPT_STOP_AT, OPT_NICE, OPT_NO_NICE, OPT_IONICE, OPT_NO_IONICE,
+      OPT_NICE_LOCAL, OPT_NICE_REMOTE, OPT_NICE_VALUE,
       OPT_REFUSED_BASE = 9000};
 
 static struct poptOption long_options[] = {
@@ -845,6 +859,22 @@ static struct poptOption long_options[] = {
   {"remote-option",   'M', POPT_ARG_STRING, 0, 'M', 0, 0 },
   {"protocol",         0,  POPT_ARG_INT,    &protocol_version, 0, 0, 0 },
   {"checksum-seed",    0,  POPT_ARG_INT,    &checksum_seed, 0, 0, 0 },
+  {"nice-local",       0,  POPT_ARG_NONE,   0, OPT_NICE_LOCAL, 0, 0 },
+  {"nice-local-value", 0,  POPT_ARG_INT,    &nice_local, 0, 0, 0 },
+  {"nice-remote",      0,  POPT_ARG_NONE,   0, OPT_NICE_REMOTE, 0, 0 },
+  {"nice-remote-value",0,  POPT_ARG_INT,    &nice_remote, 0, 0, 0 },
+  {"ionice-local",     0,  POPT_ARG_VAL,    &ionice_local, 1, 0, 0 },
+  {"ionice-remote",    0,  POPT_ARG_VAL,    &ionice_remote, 1, 0, 0 },
+  {"no-nice-local",    0,  POPT_ARG_VAL,    &nice_local, 0, 0, 0 },
+  {"no-nice-remote",   0,  POPT_ARG_VAL,    &nice_remote, 0, 0, 0 },
+  {"no-ionice-local",  0,  POPT_ARG_VAL,    &ionice_local, 0, 0, 0 },
+  {"no-ionice-remote", 0,  POPT_ARG_VAL,    &ionice_remote, 0, 0, 0 },
+  {"nice",             0,  POPT_ARG_NONE,   0, OPT_NICE, 0, 0 },
+  {"nice-value",       0,  POPT_ARG_INT,    &nice_local, OPT_NICE_VALUE, 0, 0 },
+  {"ionice",           0,  POPT_ARG_NONE,   0, OPT_IONICE, 0, 0 },
+  {"no-nice",          0,  POPT_ARG_NONE,   0, OPT_NO_NICE, 0, 0 },
+  {"no-ionice",        0,  POPT_ARG_NONE,   0, OPT_NO_IONICE, 0, 0 },
+  {"nice-and-ionice", 'Q', POPT_ARG_NONE,   0, 'Q', 0, 0 },
   {"server",           0,  POPT_ARG_NONE,   0, OPT_SERVER, 0, 0 },
   {"sender",           0,  POPT_ARG_NONE,   0, OPT_SENDER, 0, 0 },
   /* All the following options switch us into daemon-mode option-parsing. */
@@ -1365,6 +1395,7 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 	int argc = *argc_p;
 	int opt, want_dest_type;
 	int orig_protect_args = protect_args;
+	int default_nice_prio = get_renice_default_prio(); // default nice priority to be used, if no explicit priority is given.
 
 	if (argc == 0) {
 		strlcpy(err_buf, "argc is zero!\n", sizeof err_buf);
@@ -1598,6 +1629,60 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 			quiet++;
 			break;
 
+		case 'Q':
+			/*
+			 * Turn nice on with default prio when it was turned off, but do not overwrite any previously set nice value.
+			 */
+			nice_local = nice_local==0 ? default_nice_prio : nice_local;
+			nice_remote = nice_remote==0 ? default_nice_prio : nice_remote;
+			ionice_local = 1;
+			ionice_remote = 1;
+			break;
+
+		case OPT_NICE:
+			/*
+			 * Turn nice on with default prio when it was turned off, but do not overwrite any previously set nice value.
+			 */
+			nice_local = nice_local==0 ? default_nice_prio : nice_local;
+			nice_remote = nice_remote==0 ? default_nice_prio : nice_remote;
+			break;
+
+		case OPT_NICE_VALUE:
+			/*
+			 * POPT writes to nice_local. We have to copy the value from nice-local to nice-remote here.
+			 */
+			nice_remote = nice_local;
+			break;
+
+		case OPT_NICE_LOCAL:
+			/*
+			 * Turn nice on with default prio when it was turned off, but do not overwrite any previously set nice value.
+			 */
+			nice_local = nice_local==0 ? default_nice_prio : nice_local;
+			break;
+
+		case OPT_NICE_REMOTE:
+			/*
+			 * Turn nice on with default prio when it was turned off, but do not overwrite any previously set nice value.
+			 */
+			nice_remote = nice_remote==0 ? default_nice_prio : nice_remote;
+			break;
+
+		case OPT_IONICE:
+			ionice_local = 1;
+			ionice_remote = 1;
+			break;
+
+		case OPT_NO_NICE:
+			nice_local = 0;
+			nice_remote = 0;
+			break;
+
+		case OPT_NO_IONICE:
+			ionice_local = 0;
+			ionice_remote = 0;
+			break;
+
 		case 'x':
 			one_file_system++;
 			break;
@@ -2996,6 +3081,19 @@ void server_options(char **args, int *argc_p)
 	if (mkpath_dest_arg && am_sender)
 		args[ac++] = "--mkpath";
 
+	if (nice_remote) {
+		if (get_renice_default_prio()==nice_remote) {
+			args[ac++] = "--nice-local";
+		} else {
+			if (asprintf(&arg, "--nice-local-value=%d", nice_remote) < 0)
+				goto oom;
+		    args[ac++] = arg;
+		}
+	}
+
+	if (ionice_remote)
+		args[ac++] = "--ionice-local";
+
 	if (ac > MAX_SERVER_ARGS) { /* Not possible... */
 		rprintf(FERROR, "argc overflow in server_options().\n");
 		exit_cleanup(RERR_MALLOC);

rsync.1.md

@@ -559,6 +559,16 @@ has its own detailed description later in this manpage.
 --checksum-seed=NUM      set block/file checksum seed (advanced)
 --ipv4, -4               prefer IPv4
 --ipv6, -6               prefer IPv6
+--nice-local             renice local process to low priority
+--nice-remote            renice remote process to low priority
+--ionice-local           ionice local process to low priority
+--ionice-remote          ionice remote process to low priority
+--nice, --ionice         set local and remote process to low priority
+--nice-local-value=10    renice local process to given priority
+--nice-remote-value=10   renice remote process to given priority
+--nice-value=10          renice local+remote process to given priority
+--no-nice, ...           prepending "no-" turns the given option off
+--nice-and-ionice, -Q    same as --nice --ionice
 --version, -V            print the version + other info and exit
 --help, -h (*)           show this help (* -h is help only on its own)
 ```
@@ -579,6 +589,9 @@ accepted:
 --log-file=FILE          override the "log file" setting
 --log-file-format=FMT    override the "log format" setting
 --sockopts=OPTIONS       specify custom TCP options
+--nice-local             renice local daemon process to low priority
+--ionice-local           ionice local daemon process to low priority
+                         They are given at client site as (io)nice-remote
 --verbose, -v            increase verbosity
 --ipv4, -4               prefer IPv4
 --ipv6, -6               prefer IPv6

rsync.h

@@ -18,6 +18,9 @@
  * with this program; if not, visit the http://fsf.org website.
  */
 
+#ifndef RSYNC_H // Ensure that this header file is never included more than once, thus avoiding errors with duplicate definitions
+#define RSYNC_H 1
+
 #define False 0
 #define True 1
 #define Unset (-1) /* Our BOOL values are always an int. */
@@ -1510,3 +1513,17 @@ const char *get_panic_action(void);
 #elif defined HAVE_MALLINFO
 #define MEM_ALLOC_INFO mallinfo
 #endif
+
+ /* Some header files needed to be nice ;) */
+#ifdef HAVE_SYS_RESOURCE_H
+#define SUPPORT_RENICE
+#include <sys/resource.h>
+#endif
+
+#if defined HAVE_LINUX_IOPRIO_H && defined HAVE_SYS_SYSCALL_H
+#define SUPPORT_IONICE
+#include <linux/ioprio.h>
+#include <sys/syscall.h>
+#endif
+
+#endif // ifndef RSYNC_H