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TOMOYO Linux Cross Reference
Linux/kernel/rcu/Kconfig

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Diff markup

Differences between /kernel/rcu/Kconfig (Version linux-6.11.5) and /kernel/rcu/Kconfig (Version linux-6.3.13)


  1 # SPDX-License-Identifier: GPL-2.0-only             1 # SPDX-License-Identifier: GPL-2.0-only
  2 #                                                   2 #
  3 # RCU-related configuration options                 3 # RCU-related configuration options
  4 #                                                   4 #
  5                                                     5 
  6 menu "RCU Subsystem"                                6 menu "RCU Subsystem"
  7                                                     7 
  8 config TREE_RCU                                     8 config TREE_RCU
  9         bool                                        9         bool
 10         default y if SMP                           10         default y if SMP
 11         # Dynticks-idle tracking                   11         # Dynticks-idle tracking
 12         select CONTEXT_TRACKING_IDLE               12         select CONTEXT_TRACKING_IDLE
 13         help                                       13         help
 14           This option selects the RCU implemen     14           This option selects the RCU implementation that is
 15           designed for very large SMP system w     15           designed for very large SMP system with hundreds or
 16           thousands of CPUs.  It also scales d     16           thousands of CPUs.  It also scales down nicely to
 17           smaller systems.                         17           smaller systems.
 18                                                    18 
 19 config PREEMPT_RCU                                 19 config PREEMPT_RCU
 20         bool                                       20         bool
 21         default y if PREEMPTION                    21         default y if PREEMPTION
 22         select TREE_RCU                            22         select TREE_RCU
 23         help                                       23         help
 24           This option selects the RCU implemen     24           This option selects the RCU implementation that is
 25           designed for very large SMP systems      25           designed for very large SMP systems with hundreds or
 26           thousands of CPUs, but for which rea     26           thousands of CPUs, but for which real-time response
 27           is also required.  It also scales do     27           is also required.  It also scales down nicely to
 28           smaller systems.                         28           smaller systems.
 29                                                    29 
 30           Select this option if you are unsure     30           Select this option if you are unsure.
 31                                                    31 
 32 config TINY_RCU                                    32 config TINY_RCU
 33         bool                                       33         bool
 34         default y if !PREEMPT_RCU && !SMP      !!  34         default y if !PREEMPTION && !SMP
 35         help                                       35         help
 36           This option selects the RCU implemen     36           This option selects the RCU implementation that is
 37           designed for UP systems from which r     37           designed for UP systems from which real-time response
 38           is not required.  This option greatl     38           is not required.  This option greatly reduces the
 39           memory footprint of RCU.                 39           memory footprint of RCU.
 40                                                    40 
 41 config RCU_EXPERT                                  41 config RCU_EXPERT
 42         bool "Make expert-level adjustments to     42         bool "Make expert-level adjustments to RCU configuration"
 43         default n                                  43         default n
 44         help                                       44         help
 45           This option needs to be enabled if y     45           This option needs to be enabled if you wish to make
 46           expert-level adjustments to RCU conf     46           expert-level adjustments to RCU configuration.  By default,
 47           no such adjustments can be made, whi     47           no such adjustments can be made, which has the often-beneficial
 48           side-effect of preventing "make oldc     48           side-effect of preventing "make oldconfig" from asking you all
 49           sorts of detailed questions about ho     49           sorts of detailed questions about how you would like numerous
 50           obscure RCU options to be set up.        50           obscure RCU options to be set up.
 51                                                    51 
 52           Say Y if you need to make expert-lev     52           Say Y if you need to make expert-level adjustments to RCU.
 53                                                    53 
 54           Say N if you are unsure.                 54           Say N if you are unsure.
 55                                                    55 
                                                   >>  56 config SRCU
                                                   >>  57         def_bool y
                                                   >>  58 
 56 config TINY_SRCU                                   59 config TINY_SRCU
 57         bool                                       60         bool
 58         default y if TINY_RCU                      61         default y if TINY_RCU
 59         help                                       62         help
 60           This option selects the single-CPU n     63           This option selects the single-CPU non-preemptible version of SRCU.
 61                                                    64 
 62 config TREE_SRCU                                   65 config TREE_SRCU
 63         bool                                       66         bool
 64         default y if !TINY_RCU                     67         default y if !TINY_RCU
 65         help                                       68         help
 66           This option selects the full-fledged     69           This option selects the full-fledged version of SRCU.
 67                                                    70 
 68 config NEED_SRCU_NMI_SAFE                          71 config NEED_SRCU_NMI_SAFE
 69         def_bool HAVE_NMI && !ARCH_HAS_NMI_SAF     72         def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU
 70                                                    73 
 71 config TASKS_RCU_GENERIC                           74 config TASKS_RCU_GENERIC
 72         def_bool TASKS_RCU || TASKS_RUDE_RCU |     75         def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU
 73         help                                       76         help
 74           This option enables generic infrastr     77           This option enables generic infrastructure code supporting
 75           task-based RCU implementations.  Not     78           task-based RCU implementations.  Not for manual selection.
 76                                                    79 
 77 config FORCE_TASKS_RCU                             80 config FORCE_TASKS_RCU
 78         bool "Force selection of TASKS_RCU"        81         bool "Force selection of TASKS_RCU"
 79         depends on RCU_EXPERT                      82         depends on RCU_EXPERT
 80         select TASKS_RCU                           83         select TASKS_RCU
 81         default n                                  84         default n
 82         help                                       85         help
 83           This option force-enables a task-bas     86           This option force-enables a task-based RCU implementation
 84           that uses only voluntary context swi     87           that uses only voluntary context switch (not preemption!),
 85           idle, and user-mode execution as qui     88           idle, and user-mode execution as quiescent states.  Not for
 86           manual selection in most cases.          89           manual selection in most cases.
 87                                                    90 
 88 config NEED_TASKS_RCU                          << 
 89         bool                                   << 
 90         default n                              << 
 91                                                << 
 92 config TASKS_RCU                                   91 config TASKS_RCU
 93         bool                                       92         bool
 94         default NEED_TASKS_RCU && (PREEMPTION  !!  93         default n
 95         select IRQ_WORK                            94         select IRQ_WORK
 96                                                    95 
 97 config FORCE_TASKS_RUDE_RCU                        96 config FORCE_TASKS_RUDE_RCU
 98         bool "Force selection of Tasks Rude RC     97         bool "Force selection of Tasks Rude RCU"
 99         depends on RCU_EXPERT                      98         depends on RCU_EXPERT
100         select TASKS_RUDE_RCU                      99         select TASKS_RUDE_RCU
101         default n                                 100         default n
102         help                                      101         help
103           This option force-enables a task-bas    102           This option force-enables a task-based RCU implementation
104           that uses only context switch (inclu    103           that uses only context switch (including preemption) and
105           user-mode execution as quiescent sta    104           user-mode execution as quiescent states.  It forces IPIs and
106           context switches on all online CPUs,    105           context switches on all online CPUs, including idle ones,
107           so use with caution.  Not for manual    106           so use with caution.  Not for manual selection in most cases.
108                                                   107 
109 config TASKS_RUDE_RCU                             108 config TASKS_RUDE_RCU
110         bool                                      109         bool
111         default n                                 110         default n
112         select IRQ_WORK                           111         select IRQ_WORK
113                                                   112 
114 config FORCE_TASKS_TRACE_RCU                      113 config FORCE_TASKS_TRACE_RCU
115         bool "Force selection of Tasks Trace R    114         bool "Force selection of Tasks Trace RCU"
116         depends on RCU_EXPERT                     115         depends on RCU_EXPERT
117         select TASKS_TRACE_RCU                    116         select TASKS_TRACE_RCU
118         default n                                 117         default n
119         help                                      118         help
120           This option enables a task-based RCU    119           This option enables a task-based RCU implementation that uses
121           explicit rcu_read_lock_trace() read-    120           explicit rcu_read_lock_trace() read-side markers, and allows
122           these readers to appear in the idle     121           these readers to appear in the idle loop as well as on the
123           CPU hotplug code paths.  It can forc    122           CPU hotplug code paths.  It can force IPIs on online CPUs,
124           including idle ones, so use with cau    123           including idle ones, so use with caution.  Not for manual
125           selection in most cases.                124           selection in most cases.
126                                                   125 
127 config TASKS_TRACE_RCU                            126 config TASKS_TRACE_RCU
128         bool                                      127         bool
129         default n                                 128         default n
130         select IRQ_WORK                           129         select IRQ_WORK
131                                                   130 
132 config RCU_STALL_COMMON                           131 config RCU_STALL_COMMON
133         def_bool TREE_RCU                         132         def_bool TREE_RCU
134         help                                      133         help
135           This option enables RCU CPU stall co    134           This option enables RCU CPU stall code that is common between
136           the TINY and TREE variants of RCU.      135           the TINY and TREE variants of RCU.  The purpose is to allow
137           the tiny variants to disable RCU CPU    136           the tiny variants to disable RCU CPU stall warnings, while
138           making these warnings mandatory for     137           making these warnings mandatory for the tree variants.
139                                                   138 
140 config RCU_NEED_SEGCBLIST                         139 config RCU_NEED_SEGCBLIST
141         def_bool ( TREE_RCU || TREE_SRCU || TA    140         def_bool ( TREE_RCU || TREE_SRCU || TASKS_RCU_GENERIC )
142                                                   141 
143 config RCU_FANOUT                                 142 config RCU_FANOUT
144         int "Tree-based hierarchical RCU fanou    143         int "Tree-based hierarchical RCU fanout value"
145         range 2 64 if 64BIT                       144         range 2 64 if 64BIT
146         range 2 32 if !64BIT                      145         range 2 32 if !64BIT
147         depends on TREE_RCU && RCU_EXPERT         146         depends on TREE_RCU && RCU_EXPERT
148         default 64 if 64BIT                       147         default 64 if 64BIT
149         default 32 if !64BIT                      148         default 32 if !64BIT
150         help                                      149         help
151           This option controls the fanout of h    150           This option controls the fanout of hierarchical implementations
152           of RCU, allowing RCU to work efficie    151           of RCU, allowing RCU to work efficiently on machines with
153           large numbers of CPUs.  This value m    152           large numbers of CPUs.  This value must be at least the fourth
154           root of NR_CPUS, which allows NR_CPU    153           root of NR_CPUS, which allows NR_CPUS to be insanely large.
155           The default value of RCU_FANOUT shou    154           The default value of RCU_FANOUT should be used for production
156           systems, but if you are stress-testi    155           systems, but if you are stress-testing the RCU implementation
157           itself, small RCU_FANOUT values allo    156           itself, small RCU_FANOUT values allow you to test large-system
158           code paths on small(er) systems.        157           code paths on small(er) systems.
159                                                   158 
160           Select a specific number if testing     159           Select a specific number if testing RCU itself.
161           Take the default if unsure.             160           Take the default if unsure.
162                                                   161 
163 config RCU_FANOUT_LEAF                            162 config RCU_FANOUT_LEAF
164         int "Tree-based hierarchical RCU leaf-    163         int "Tree-based hierarchical RCU leaf-level fanout value"
165         range 2 64 if 64BIT && !RCU_STRICT_GRA    164         range 2 64 if 64BIT && !RCU_STRICT_GRACE_PERIOD
166         range 2 32 if !64BIT && !RCU_STRICT_GR    165         range 2 32 if !64BIT && !RCU_STRICT_GRACE_PERIOD
167         range 2 3 if RCU_STRICT_GRACE_PERIOD      166         range 2 3 if RCU_STRICT_GRACE_PERIOD
168         depends on TREE_RCU && RCU_EXPERT         167         depends on TREE_RCU && RCU_EXPERT
169         default 16 if !RCU_STRICT_GRACE_PERIOD    168         default 16 if !RCU_STRICT_GRACE_PERIOD
170         default 2 if RCU_STRICT_GRACE_PERIOD      169         default 2 if RCU_STRICT_GRACE_PERIOD
171         help                                      170         help
172           This option controls the leaf-level     171           This option controls the leaf-level fanout of hierarchical
173           implementations of RCU, and allows t    172           implementations of RCU, and allows trading off cache misses
174           against lock contention.  Systems th    173           against lock contention.  Systems that synchronize their
175           scheduling-clock interrupts for ener    174           scheduling-clock interrupts for energy-efficiency reasons will
176           want the default because the smaller    175           want the default because the smaller leaf-level fanout keeps
177           lock contention levels acceptably lo    176           lock contention levels acceptably low.  Very large systems
178           (hundreds or thousands of CPUs) will    177           (hundreds or thousands of CPUs) will instead want to set this
179           value to the maximum value possible     178           value to the maximum value possible in order to reduce the
180           number of cache misses incurred duri    179           number of cache misses incurred during RCU's grace-period
181           initialization.  These systems tend     180           initialization.  These systems tend to run CPU-bound, and thus
182           are not helped by synchronized inter    181           are not helped by synchronized interrupts, and thus tend to
183           skew them, which reduces lock conten    182           skew them, which reduces lock contention enough that large
184           leaf-level fanouts work well.  That     183           leaf-level fanouts work well.  That said, setting leaf-level
185           fanout to a large number will likely    184           fanout to a large number will likely cause problematic
186           lock contention on the leaf-level rc    185           lock contention on the leaf-level rcu_node structures unless
187           you boot with the skew_tick kernel p    186           you boot with the skew_tick kernel parameter.
188                                                   187 
189           Select a specific number if testing     188           Select a specific number if testing RCU itself.
190                                                   189 
191           Select the maximum permissible value    190           Select the maximum permissible value for large systems, but
192           please understand that you may also     191           please understand that you may also need to set the skew_tick
193           kernel boot parameter to avoid conte    192           kernel boot parameter to avoid contention on the rcu_node
194           structure's locks.                      193           structure's locks.
195                                                   194 
196           Take the default if unsure.             195           Take the default if unsure.
197                                                   196 
198 config RCU_BOOST                                  197 config RCU_BOOST
199         bool "Enable RCU priority boosting"       198         bool "Enable RCU priority boosting"
200         depends on (RT_MUTEXES && PREEMPT_RCU     199         depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT
201         default y if PREEMPT_RT                   200         default y if PREEMPT_RT
202         help                                      201         help
203           This option boosts the priority of p    202           This option boosts the priority of preempted RCU readers that
204           block the current preemptible RCU gr    203           block the current preemptible RCU grace period for too long.
205           This option also prevents heavy load    204           This option also prevents heavy loads from blocking RCU
206           callback invocation.                    205           callback invocation.
207                                                   206 
208           Say Y here if you are working with r    207           Say Y here if you are working with real-time apps or heavy loads
209           Say N here if you are unsure.           208           Say N here if you are unsure.
210                                                   209 
211 config RCU_BOOST_DELAY                            210 config RCU_BOOST_DELAY
212         int "Milliseconds to delay boosting af    211         int "Milliseconds to delay boosting after RCU grace-period start"
213         range 0 3000                              212         range 0 3000
214         depends on RCU_BOOST                      213         depends on RCU_BOOST
215         default 500                               214         default 500
216         help                                      215         help
217           This option specifies the time to wa    216           This option specifies the time to wait after the beginning of
218           a given grace period before priority    217           a given grace period before priority-boosting preempted RCU
219           readers blocking that grace period.     218           readers blocking that grace period.  Note that any RCU reader
220           blocking an expedited RCU grace peri    219           blocking an expedited RCU grace period is boosted immediately.
221                                                   220 
222           Accept the default if unsure.           221           Accept the default if unsure.
223                                                   222 
224 config RCU_EXP_KTHREAD                            223 config RCU_EXP_KTHREAD
225         bool "Perform RCU expedited work in a     224         bool "Perform RCU expedited work in a real-time kthread"
226         depends on RCU_BOOST && RCU_EXPERT        225         depends on RCU_BOOST && RCU_EXPERT
227         default !PREEMPT_RT && NR_CPUS <= 32      226         default !PREEMPT_RT && NR_CPUS <= 32
228         help                                      227         help
229           Use this option to further reduce th    228           Use this option to further reduce the latencies of expedited
230           grace periods at the expense of bein    229           grace periods at the expense of being more disruptive.
231                                                   230 
232           This option is disabled by default o    231           This option is disabled by default on PREEMPT_RT=y kernels which
233           disable expedited grace periods afte    232           disable expedited grace periods after boot by unconditionally
234           setting rcupdate.rcu_normal_after_bo    233           setting rcupdate.rcu_normal_after_boot=1.
235                                                   234 
236           Accept the default if unsure.           235           Accept the default if unsure.
237                                                   236 
238 config RCU_NOCB_CPU                               237 config RCU_NOCB_CPU
239         bool "Offload RCU callback processing     238         bool "Offload RCU callback processing from boot-selected CPUs"
240         depends on TREE_RCU                       239         depends on TREE_RCU
241         depends on RCU_EXPERT || NO_HZ_FULL       240         depends on RCU_EXPERT || NO_HZ_FULL
242         default n                                 241         default n
243         help                                      242         help
244           Use this option to reduce OS jitter     243           Use this option to reduce OS jitter for aggressive HPC or
245           real-time workloads.  It can also be    244           real-time workloads.  It can also be used to offload RCU
246           callback invocation to energy-effici    245           callback invocation to energy-efficient CPUs in battery-powered
247           asymmetric multiprocessors.  The pri    246           asymmetric multiprocessors.  The price of this reduced jitter
248           is that the overhead of call_rcu() i    247           is that the overhead of call_rcu() increases and that some
249           workloads will incur significant inc    248           workloads will incur significant increases in context-switch
250           rates.                                  249           rates.
251                                                   250 
252           This option offloads callback invoca    251           This option offloads callback invocation from the set of CPUs
253           specified at boot time by the rcu_no    252           specified at boot time by the rcu_nocbs parameter.  For each
254           such CPU, a kthread ("rcuox/N") will    253           such CPU, a kthread ("rcuox/N") will be created to invoke
255           callbacks, where the "N" is the CPU     254           callbacks, where the "N" is the CPU being offloaded, and where
256           the "x" is "p" for RCU-preempt (PREE    255           the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for
257           RCU-sched (!PREEMPTION kernels).  No    256           RCU-sched (!PREEMPTION kernels).  Nothing prevents this kthread
258           from running on the specified CPUs,     257           from running on the specified CPUs, but (1) the kthreads may be
259           preempted between each callback, and    258           preempted between each callback, and (2) affinity or cgroups can
260           be used to force the kthreads to run    259           be used to force the kthreads to run on whatever set of CPUs is
261           desired.                                260           desired.
262                                                   261 
263           Say Y here if you need reduced OS ji    262           Say Y here if you need reduced OS jitter, despite added overhead.
264           Say N here if you are unsure.           263           Say N here if you are unsure.
265                                                   264 
266 config RCU_NOCB_CPU_DEFAULT_ALL                   265 config RCU_NOCB_CPU_DEFAULT_ALL
267         bool "Offload RCU callback processing     266         bool "Offload RCU callback processing from all CPUs by default"
268         depends on RCU_NOCB_CPU                   267         depends on RCU_NOCB_CPU
269         default n                                 268         default n
270         help                                      269         help
271           Use this option to offload callback     270           Use this option to offload callback processing from all CPUs
272           by default, in the absence of the rc    271           by default, in the absence of the rcu_nocbs or nohz_full boot
273           parameter. This also avoids the need    272           parameter. This also avoids the need to use any boot parameters
274           to achieve the effect of offloading     273           to achieve the effect of offloading all CPUs on boot.
275                                                   274 
276           Say Y here if you want offload all C    275           Say Y here if you want offload all CPUs by default on boot.
277           Say N here if you are unsure.           276           Say N here if you are unsure.
278                                                   277 
279 config RCU_NOCB_CPU_CB_BOOST                      278 config RCU_NOCB_CPU_CB_BOOST
280         bool "Offload RCU callback from real-t    279         bool "Offload RCU callback from real-time kthread"
281         depends on RCU_NOCB_CPU && RCU_BOOST      280         depends on RCU_NOCB_CPU && RCU_BOOST
282         default y if PREEMPT_RT                   281         default y if PREEMPT_RT
283         help                                      282         help
284           Use this option to invoke offloaded     283           Use this option to invoke offloaded callbacks as SCHED_FIFO
285           to avoid starvation by heavy SCHED_O    284           to avoid starvation by heavy SCHED_OTHER background load.
286           Of course, running as SCHED_FIFO dur    285           Of course, running as SCHED_FIFO during callback floods will
287           cause the rcuo[ps] kthreads to monop    286           cause the rcuo[ps] kthreads to monopolize the CPU for hundreds
288           of milliseconds or more.  Therefore,    287           of milliseconds or more.  Therefore, when enabling this option,
289           it is your responsibility to ensure     288           it is your responsibility to ensure that latency-sensitive
290           tasks either run with higher priorit    289           tasks either run with higher priority or run on some other CPU.
291                                                   290 
292           Say Y here if you want to set RT pri    291           Say Y here if you want to set RT priority for offloading kthreads.
293           Say N here if you are building a !PR    292           Say N here if you are building a !PREEMPT_RT kernel and are unsure.
294                                                   293 
295 config TASKS_TRACE_RCU_READ_MB                    294 config TASKS_TRACE_RCU_READ_MB
296         bool "Tasks Trace RCU readers use memo    295         bool "Tasks Trace RCU readers use memory barriers in user and idle"
297         depends on RCU_EXPERT && TASKS_TRACE_R    296         depends on RCU_EXPERT && TASKS_TRACE_RCU
298         default PREEMPT_RT || NR_CPUS < 8         297         default PREEMPT_RT || NR_CPUS < 8
299         help                                      298         help
300           Use this option to further reduce th    299           Use this option to further reduce the number of IPIs sent
301           to CPUs executing in userspace or id    300           to CPUs executing in userspace or idle during tasks trace
302           RCU grace periods.  Given that a rea    301           RCU grace periods.  Given that a reasonable setting of
303           the rcupdate.rcu_task_ipi_delay kern    302           the rcupdate.rcu_task_ipi_delay kernel boot parameter
304           eliminates such IPIs for many worklo    303           eliminates such IPIs for many workloads, proper setting
305           of this Kconfig option is important     304           of this Kconfig option is important mostly for aggressive
306           real-time installations and for batt    305           real-time installations and for battery-powered devices,
307           hence the default chosen above.         306           hence the default chosen above.
308                                                   307 
309           Say Y here if you hate IPIs.            308           Say Y here if you hate IPIs.
310           Say N here if you hate read-side mem    309           Say N here if you hate read-side memory barriers.
311           Take the default if you are unsure.     310           Take the default if you are unsure.
312                                                   311 
313 config RCU_LAZY                                   312 config RCU_LAZY
314         bool "RCU callback lazy invocation fun    313         bool "RCU callback lazy invocation functionality"
315         depends on RCU_NOCB_CPU                   314         depends on RCU_NOCB_CPU
316         default n                                 315         default n
317         help                                      316         help
318           To save power, batch RCU callbacks a    317           To save power, batch RCU callbacks and flush after delay, memory
319           pressure, or callback list growing t    318           pressure, or callback list growing too big.
320                                                << 
321           Requires rcu_nocbs=all to be set.    << 
322                                                << 
323           Use rcutree.enable_rcu_lazy=0 to tur << 
324                                                << 
325 config RCU_LAZY_DEFAULT_OFF                    << 
326         bool "Turn RCU lazy invocation off by  << 
327         depends on RCU_LAZY                    << 
328         default n                              << 
329         help                                   << 
330           Allows building the kernel with CONF << 
331           off. Boot time param rcutree.enable_ << 
332           it back on.                          << 
333                                                << 
334 config RCU_DOUBLE_CHECK_CB_TIME                << 
335         bool "RCU callback-batch backup time c << 
336         depends on RCU_EXPERT                  << 
337         default n                              << 
338         help                                   << 
339           Use this option to provide more prec << 
340           rcutree.rcu_resched_ns module parame << 
341           a single RCU callback might run for  << 
342           thus defeating the 32-callback batch << 
343           cost of the fine-grained but expensi << 
344                                                << 
345           This option rounds rcutree.rcu_resch << 
346           jiffy, and overrides the 32-callback << 
347           is exceeded.                         << 
348                                                << 
349           Say Y here if you need tighter callb << 
350           Say N here if you are unsure.        << 
351                                                   319 
352 endmenu # "RCU Subsystem"                         320 endmenu # "RCU Subsystem"
                                                      

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