summaryrefslogtreecommitdiff
path: root/src/dev/arm/flash_device.cc
blob: 297354b650a5136cdbf7dbe3cd77011820b0575f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
/*
 * Copyright (c) 2013-2015 ARM Limited
 * All rights reserved
 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
 * unmodified and in its entirety in all distributions of the software,
 * modified or unmodified, in source code or in binary form.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Authors: Rene de Jong
 */

/** @file
 * This simplistic flash model is designed to model managed SLC NAND flash.
 * This device will need an interface module (such as NVMe or UFS); Note that
 * this model only calculates the delay and does not perform the actual
 * transaction.
 *
 * To access the memory, use either readMemory or writeMemory. This will
 * schedule an event at the tick where the action will finish. If a callback
 * has been given as argument then that function will be called on completion
 * of that event. Note that this does not guarantee that there are no other
 * actions pending in the flash device.
 *
 * IMPORTANT: number of planes should be a power of 2.
 */

#include "dev/arm/flash_device.hh"

#include "debug/Drain.hh"

/**
 * Create this device
 */

FlashDevice*
FlashDeviceParams::create()
{
    return new FlashDevice(this);
}


/**
 * Flash Device constructor and destructor
 */

FlashDevice::FlashDevice(const FlashDeviceParams* p):
    AbstractNVM(p),
    diskSize(0),
    blockSize(p->blk_size),
    pageSize(p->page_size),
    GCActivePercentage(p->GC_active),
    readLatency(p->read_lat),
    writeLatency(p->write_lat),
    eraseLatency(p->erase_lat),
    dataDistribution(p->data_distribution),
    numPlanes(p->num_planes),
    pagesPerBlock(0),
    pagesPerDisk(0),
    blocksPerDisk(0),
    planeMask(numPlanes - 1),
    planeEventQueue(numPlanes),
    planeEvent(this)
{

    /*
     * Let 'a' be a power of two of n bits, written such that a-n is the msb
     * and a-0 is the lsb. Since it is a power of two, only one bit (a-x,
     * with 0 <= x <= n) is set. If we subtract one from this number the bits
     * a-(x-1) to a-0 are set and all the other bits are cleared. Hence a
     * bitwise AND with those two numbers results in an integer with all bits
     * cleared.
     */
    if (numPlanes & planeMask)
        fatal("Number of planes is not a power of 2 in flash device.\n");
}

/**
 * Initiates all the flash functions: initializes the lookup tables, age of
 * the device, etc. This can only be done once the disk image is known.
 * Thats why it can't be done in the constructor.
 */
void
FlashDevice::initializeFlash(uint64_t disk_size, uint32_t sector_size)
{
    diskSize = disk_size * sector_size;
    pagesPerBlock = blockSize / pageSize;
    pagesPerDisk = diskSize / pageSize;
    blocksPerDisk = diskSize / blockSize;

    /** Sanity information: check flash configuration */
    DPRINTF(FlashDevice, "diskSize: %d Bytes; %d pages per block, %d pages "
            "per disk\n", diskSize, pagesPerBlock, pagesPerDisk);

    locationTable.resize(pagesPerDisk);

    /**Garbage collection related*/
    blockValidEntries.resize(blocksPerDisk, 0);
    blockEmptyEntries.resize(blocksPerDisk, pagesPerBlock);

    /**
     * This is a bitmap. Every bit is a page
     * unknownPages is a vector of 32 bit integers. If every page was an
     * integer, the total size would be pagesPerDisk; since we can map one
     * page per bit we need ceil(pagesPerDisk/32) entries. 32 = 1 << 5 hence
     * it will do to just shift pagesPerDisk five positions and add one. This
     * will allocate one integer to many for this data structure in the worst
     * case.
     */
    unknownPages.resize((pagesPerDisk >> 5) + 1, 0xFFFFFFFF);

    for (uint32_t count = 0; count < pagesPerDisk; count++) {
        //setup lookup table + physical aspects

        if (dataDistribution == Enums::stripe) {
            locationTable[count].page = count / blocksPerDisk;
            locationTable[count].block = count % blocksPerDisk;

        } else {
            locationTable[count].page = count % pagesPerBlock;
            locationTable[count].block = count / pagesPerBlock;
        }
    }
}

FlashDevice::~FlashDevice()
{
    DPRINTF(FlashDevice, "Remove FlashDevice\n");
}

/**
 * Handles the accesses to the device.
 * The function determines when certain actions are scheduled and schedules
 * an event that uses the callback function on completion of the action.
 */
void
FlashDevice::accessDevice(uint64_t address, uint32_t amount, Callback *event,
                          Actions action)
{
    DPRINTF(FlashDevice, "Flash calculation for %d bytes in %d pages\n"
            , amount, pageSize);

    std::vector<Tick> time(numPlanes, 0);
    uint64_t logic_page_addr = address / pageSize;
    uint32_t plane_address = 0;

    /**
     * The access will be broken up in a number of page accesses. The number
     * of page accesses depends on the amount that needs to be transfered.
     * The assumption here is that the interface is completely ignorant of
     * the page size and that this model has to figure out all of the
     * transaction characteristics.
     */
    for (uint32_t count = 0; amount > (count * pageSize); count++) {
        uint32_t index = (locationTable[logic_page_addr].block *
                          pagesPerBlock) + (logic_page_addr % pagesPerBlock);

        DPRINTF(FlashDevice, "Index 0x%8x, Block 0x%8x, pages/block %d,"
                " logic address 0x%8x\n", index,
                locationTable[logic_page_addr].block, pagesPerBlock,
                logic_page_addr);
        DPRINTF(FlashDevice, "Page %d; %d bytes up to this point\n", count,
                (count * pageSize));

        plane_address = locationTable[logic_page_addr].block & planeMask;

        if (action == ActionRead) {
            //lookup
            //call accessTimes
            time[plane_address] += accessTimes(locationTable[logic_page_addr]
                                               .block, ActionRead);

            /*stats*/
            stats.readAccess.sample(logic_page_addr);
            stats.readLatency.sample(time[plane_address]);
        } else { //write
            //lookup
            //call accessTimes if appropriate, page may be unknown, so lets
            //give it the benefit of the doubt

            if (getUnknownPages(index))
                time[plane_address] += accessTimes
                    (locationTable[logic_page_addr].block, ActionWrite);

            else //A remap is needed
                time[plane_address] += remap(logic_page_addr);

            /*stats*/
            stats.writeAccess.sample(logic_page_addr);
            stats.writeLatency.sample(time[plane_address]);
        }

        /**
         * Check if the page is known and used. unknownPages is a bitmap of
         * all the pages. It tracks wether we can be sure that the
         * information of this page is taken into acount in the model (is it
         * considered in blockValidEntries and blockEmptyEntries?). If it has
         * been used in the past, then it is known.
         */
        if (getUnknownPages(index)) {
            clearUnknownPages(index);
            --blockEmptyEntries[locationTable[logic_page_addr].block];
            ++blockValidEntries[locationTable[logic_page_addr].block];
        }

        stats.fileSystemAccess.sample(address);
        ++logic_page_addr;
    }

    /**
     * previous part of the function found the times spend in different
     * planes, now lets find the maximum to know when to callback the disk
     */
    for (uint32_t count = 0; count < numPlanes; count++){
        plane_address = (time[plane_address] > time[count]) ? plane_address
            : count;

        DPRINTF(FlashDevice, "Plane %d is busy for %d ticks\n", count,
                time[count]);

        if (time[count] != 0) {

            struct CallBackEntry cbe;
            /**
             * If there are no events for this plane, then add the current
             * time to the occupation time; otherwise, plan it after the
             * last event. If by chance that event is handled in this tick,
             * then we would still end up with the same result.
             */
            if (planeEventQueue[count].empty())
                cbe.time = time[count] + curTick();
            else
                cbe.time = time[count] +
                           planeEventQueue[count].back().time;
            cbe.function = NULL;
            planeEventQueue[count].push_back(cbe);

            DPRINTF(FlashDevice, "scheduled at: %ld\n", cbe.time);

            if (!planeEvent.scheduled())
                schedule(planeEvent, planeEventQueue[count].back().time);
            else if (planeEventQueue[count].back().time < planeEvent.when())
                reschedule(planeEvent,
                    planeEventQueue[plane_address].back().time, true);
        }
    }

    //worst case two plane finish at the same time, each triggers an event
    //and this callback will be called once. Maybe before the other plane
    //could execute its event, but in the same tick.
    planeEventQueue[plane_address].back().function = event;
    DPRINTF(FlashDevice, "Callback queued for plane %d; %d in queue\n",
            plane_address, planeEventQueue[plane_address].size());
    DPRINTF(FlashDevice, "first event @ %d\n", planeEvent.when());
}

/**
 * When a plane completes its action, this event is triggered. When a
 * callback function was associated with that event, it will be called.
 */

void
FlashDevice::actionComplete()
{
    DPRINTF(FlashDevice, "Plane action completed\n");
    uint8_t plane_address = 0;

    uint8_t next_event = 0;

    /**Search for a callback that is supposed to happen in this Tick*/
    for (plane_address = 0; plane_address < numPlanes; plane_address++) {
        if (!planeEventQueue[plane_address].empty()) {
            /**
             * Invariant: All queued events are scheduled in the present
             *  or future.
             */
            assert(planeEventQueue[plane_address].front().time >= curTick());

            if (planeEventQueue[plane_address].front().time == curTick()) {
                /**
                 * To ensure that the follow-up action is executed correctly,
                 * the callback entry first need to be cleared before it can
                 * be called.
                 */
                Callback *temp = planeEventQueue[plane_address].front().
                                 function;
                planeEventQueue[plane_address].pop_front();

                /**Found a callback, lets make it happen*/
                if (temp != NULL) {
                    DPRINTF(FlashDevice, "Callback, %d\n", plane_address);
                    temp->process();
                }
            }
        }
    }

    /** Find when to schedule the planeEvent next */
    for (plane_address = 0; plane_address < numPlanes; plane_address++) {
        if (!planeEventQueue[plane_address].empty())
            if (planeEventQueue[next_event].empty() ||
                    (planeEventQueue[plane_address].front().time <
                     planeEventQueue[next_event].front().time))
                next_event = plane_address;
    }

    /**Schedule the next plane that will be ready (if any)*/
    if (!planeEventQueue[next_event].empty()) {
        DPRINTF(FlashDevice, "Schedule plane: %d\n", plane_address);
        reschedule(planeEvent, planeEventQueue[next_event].front().time, true);
    }

    checkDrain();

    DPRINTF(FlashDevice, "returing from flash event\n");
    DPRINTF(FlashDevice, "first event @ %d\n", planeEvent.when());
}

/**
 * Handles the remapping of the pages. It is a (I hope) sensible statistic
 * approach. asumption: garbage collection happens when a clean is needed
 * (may become stochastic function).
 */
Tick
FlashDevice::remap(uint64_t logic_page_addr)
{
    /**
     * Are there any empty left in this Block, or do we need to do an erase
     */
    if (blockEmptyEntries[locationTable[logic_page_addr].block] > 0) {
        //just a remap
        //update tables
        --blockEmptyEntries[locationTable[logic_page_addr].block];
        //access to this table won't be sequential anymore
        locationTable[logic_page_addr].page = pagesPerBlock + 2;
        //access new block
        Tick time = accessTimes(locationTable[logic_page_addr].block,
                                ActionWrite);

        DPRINTF(FlashDevice, "Remap returns %d ticks\n", time);
        return time;

    } else {
        //calculate how much time GC would have taken
        uint32_t block = locationTable[logic_page_addr].block;
        Tick time = ((GCActivePercentage *
                       (accessTimes(block, ActionCopy) +
                        accessTimes(block, ActionErase)))
                     / 100);

        //use block as the logical start address of the block
        block = locationTable[logic_page_addr].block * pagesPerBlock;

        //assumption: clean will improve locality
        for (uint32_t count = 0; count < pagesPerBlock; count++) {
            assert(block + count < pagesPerDisk);
            locationTable[block + count].page = (block + count) %
                pagesPerBlock;
            ++count;
        }

        blockEmptyEntries[locationTable[logic_page_addr].block] =
            pagesPerBlock;
        /*stats*/
        ++stats.totalGCActivations;

        DPRINTF(FlashDevice, "Remap with erase action returns %d ticks\n",
                time);

        return time;
    }

}

/**
 * Calculates the accesstime per operation needed
 */
Tick
FlashDevice::accessTimes(uint64_t block, Actions action)
{
    Tick time = 0;

    switch(action) {
      case ActionRead: {
          /**Just read the page*/
          time = readLatency;
      } break;

      case ActionWrite: {
          /**Write the page, and read the result*/
          time = writeLatency + readLatency;
      } break;

      case ActionErase: {
          /**Erase and check wether it was successfull*/
          time = eraseLatency + readLatency;
      } break;

      case ActionCopy: {
          /**Copy every valid page*/
          uint32_t validpages = blockValidEntries[block];
          time = validpages * (readLatency + writeLatency);
      } break;

      default: break;
    }

    //Used to determine sequential action.
    DPRINTF(FlashDevice, "Access returns %d ticks\n", time);
    return time;
}

/**
 * clearUnknownPages. defines that a page is known and used
 * unknownPages is a bitmap of all the pages. It tracks wether we can be sure
 * that the information of this page is taken into acount in the model (is it
 * considered in blockValidEntries and blockEmptyEntries?). If it has been
 * used in the past, then it is known. But it needs to be tracked to make
 * decisions about write accesses, and indirectly about copy actions. one
 * unknownPage entry is a 32 bit integer. So if we have a page index, then
 * that means that we need entry floor(index/32) (index >> 5) and we need to
 * select the bit which number is equal to the remainder of index/32
 * (index%32). The bit is cleared to make sure that we see it as considered
 * in the future.
 */

inline
void
FlashDevice::clearUnknownPages(uint32_t index)
{
    unknownPages[index >> 5] &= ~(0x01 << (index % 32));
}

/**
 * getUnknownPages. Verify wether a page is known
 */

inline
bool
FlashDevice::getUnknownPages(uint32_t index)
{
    return unknownPages[index >> 5] & (0x01 << (index % 32));
}

void
FlashDevice::regStats()
{
    AbstractNVM::regStats();

    using namespace Stats;

    std::string fd_name = name() + ".FlashDevice";

    // Register the stats
    /** Amount of GC activations*/
    stats.totalGCActivations
        .name(fd_name + ".totalGCActivations")
        .desc("Number of Garbage collector activations")
        .flags(none);

    /** Histogram of address accesses*/
    stats.writeAccess
        .init(2)
        .name(fd_name + ".writeAccessHist")
        .desc("Histogram of write addresses")
        .flags(pdf);
    stats.readAccess
        .init(2)
        .name(fd_name + ".readAccessHist")
        .desc("Histogram of read addresses")
        .flags(pdf);
    stats.fileSystemAccess
        .init(100)
        .name(fd_name + ".fileSystemAccessHist")
        .desc("Histogram of file system accesses")
        .flags(pdf);

    /** Histogram of access latencies*/
    stats.writeLatency
        .init(100)
        .name(fd_name + ".writeLatencyHist")
        .desc("Histogram of write latency")
        .flags(pdf);
    stats.readLatency
        .init(100)
        .name(fd_name + ".readLatencyHist")
        .desc("Histogram of read latency")
        .flags(pdf);
}

/**
 * Serialize; needed to create checkpoints
 */

void
FlashDevice::serialize(CheckpointOut &cp) const
{
    SERIALIZE_SCALAR(planeMask);

    SERIALIZE_CONTAINER(unknownPages);
    SERIALIZE_CONTAINER(blockValidEntries);
    SERIALIZE_CONTAINER(blockEmptyEntries);

    int location_table_size = locationTable.size();
    SERIALIZE_SCALAR(location_table_size);
    for (uint32_t count = 0; count < location_table_size; count++) {
        paramOut(cp, csprintf("locationTable[%d].page", count),
                 locationTable[count].page);
        paramOut(cp, csprintf("locationTable[%d].block", count),
                 locationTable[count].block);
    }
};

/**
 * Unserialize; needed to restore from checkpoints
 */

void
FlashDevice::unserialize(CheckpointIn &cp)
{
    UNSERIALIZE_SCALAR(planeMask);

    UNSERIALIZE_CONTAINER(unknownPages);
    UNSERIALIZE_CONTAINER(blockValidEntries);
    UNSERIALIZE_CONTAINER(blockEmptyEntries);

    int location_table_size;
    UNSERIALIZE_SCALAR(location_table_size);
    locationTable.resize(location_table_size);
    for (uint32_t count = 0; count < location_table_size; count++) {
        paramIn(cp, csprintf("locationTable[%d].page", count),
                locationTable[count].page);
        paramIn(cp, csprintf("locationTable[%d].block", count),
                locationTable[count].block);
    }
};

/**
 * Drain; needed to enable checkpoints
 */

DrainState
FlashDevice::drain()
{
    if (planeEvent.scheduled()) {
        DPRINTF(Drain, "Flash device is draining...\n");
        return DrainState::Draining;
    } else {
        DPRINTF(Drain, "Flash device in drained state\n");
        return DrainState::Drained;
    }
}

/**
 * Checkdrain; needed to enable checkpoints
 */

void
FlashDevice::checkDrain()
{
    if (drainState() != DrainState::Draining)
        return;

    if (planeEvent.when() > curTick()) {
        DPRINTF(Drain, "Flash device is still draining\n");
    } else {
        DPRINTF(Drain, "Flash device is done draining\n");
        signalDrainDone();
    }
}