From: Shushu Yi <firnyee@xxxxxxxxx> <changelog> Optimized by using fine-grained locks, customized data structures, and scattered address space. Achieves significant improvements in both throughput and latency. This patch attempts to maximize thread-level parallelism and reduce CPU suspension time caused by lock contention. On a system with four PCIe 4.0 SSDs, we achieved increased overall storage throughput by 89.4% and decreases the 99.99th percentile I/O latency by 85.4%. Seeking feedback on the approach and any addition information regarding Required performance testing before submitting a formal patch. Note: this work has been published as a paper, and the URL is (https://www.hotstorage.org/2022/camera-ready/hotstorage22-5/pdf/ hotstorage22-5.pdf) Co-developed-by: Yiming Xu <teddyxym@xxxxxxxxxxx> Signed-off-by: Yiming Xu <teddyxym@xxxxxxxxxxx> Signed-off-by: Shushu Yi <firnyee@xxxxxxxxx> Tested-by: Paul Luse <paul.e.luse@xxxxxxxxx> --- V1 -> V2: Cleaned up coding style and divided into 2 patches (HemiRAID and ScalaRAID corresponding to the paper mentioned above). This part is ScalaRAID, which equipped every counter with a counter lock and employ our D-Block. drivers/md/md-bitmap.c | 197 ++++++++++++++++++++++++++++++----------- drivers/md/md-bitmap.h | 12 ++- 2 files changed, 154 insertions(+), 55 deletions(-) diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c index 059afc24c08b..5ed5fe810b2f 100644 --- a/drivers/md/md-bitmap.c +++ b/drivers/md/md-bitmap.c @@ -47,10 +47,12 @@ static inline char *bmname(struct bitmap *bitmap) * if we find our page, we increment the page's refcount so that it stays * allocated while we're using it */ -static int md_bitmap_checkpage(struct bitmap_counts *bitmap, - unsigned long page, int create, int no_hijack) -__releases(bitmap->lock) -__acquires(bitmap->lock) +static int md_bitmap_checkpage(struct bitmap_counts *bitmap, unsigned long page, + int create, int no_hijack, spinlock_t *bmclock, int locktype) +__releases(bmclock) +__acquires(bmclock) +__releases(bitmap->mlock) +__acquires(bitmap->mlock) { unsigned char *mappage; @@ -65,8 +67,10 @@ __acquires(bitmap->lock) return -ENOENT; /* this page has not been allocated yet */ - - spin_unlock_irq(&bitmap->lock); + if (locktype) + spin_unlock_irq(bmclock); + else + write_unlock_irq(&bitmap->mlock); /* It is possible that this is being called inside a * prepare_to_wait/finish_wait loop from raid5c:make_request(). * In general it is not permitted to sleep in that context as it @@ -81,7 +85,11 @@ __acquires(bitmap->lock) */ sched_annotate_sleep(); mappage = kzalloc(PAGE_SIZE, GFP_NOIO); - spin_lock_irq(&bitmap->lock); + + if (locktype) + spin_lock_irq(bmclock); + else + write_lock_irq(&bitmap->mlock); if (mappage == NULL) { pr_debug("md/bitmap: map page allocation failed, hijacking\n"); @@ -399,7 +407,7 @@ static int read_file_page(struct file *file, unsigned long index, } wait_event(bitmap->write_wait, - atomic_read(&bitmap->pending_writes)==0); + atomic_read(&bitmap->pending_writes) == 0); if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags)) ret = -EIO; out: @@ -458,7 +466,7 @@ static void md_bitmap_wait_writes(struct bitmap *bitmap) { if (bitmap->storage.file) wait_event(bitmap->write_wait, - atomic_read(&bitmap->pending_writes)==0); + atomic_read(&bitmap->pending_writes) == 0); else /* Note that we ignore the return value. The writes * might have failed, but that would just mean that @@ -1248,16 +1256,28 @@ void md_bitmap_write_all(struct bitmap *bitmap) static void md_bitmap_count_page(struct bitmap_counts *bitmap, sector_t offset, int inc) { - sector_t chunk = offset >> bitmap->chunkshift; - unsigned long page = chunk >> PAGE_COUNTER_SHIFT; + sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT); + sector_t totblocks = bitmap->chunks << (bitmap->chunkshift - (PAGE_SHIFT - SECTOR_SHIFT)); + unsigned long bits = totblocks ? fls((totblocks - 1)) : 0; + unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX << + (bits - (bitmap->chunkshift + SECTOR_SHIFT - PAGE_SHIFT))); + unsigned long cntid = blockno & mask; + unsigned long page = cntid >> PAGE_COUNTER_SHIFT; + bitmap->bp[page].count += inc; md_bitmap_checkfree(bitmap, page); } static void md_bitmap_set_pending(struct bitmap_counts *bitmap, sector_t offset) { - sector_t chunk = offset >> bitmap->chunkshift; - unsigned long page = chunk >> PAGE_COUNTER_SHIFT; + sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT); + sector_t totblocks = bitmap->chunks << (bitmap->chunkshift - (PAGE_SHIFT - SECTOR_SHIFT)); + unsigned long bits = totblocks ? fls((totblocks - 1)) : 0; + unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX << + (bits - (bitmap->chunkshift + SECTOR_SHIFT - PAGE_SHIFT))); + unsigned long cntid = blockno & mask; + unsigned long page = cntid >> PAGE_COUNTER_SHIFT; + struct bitmap_page *bp = &bitmap->bp[page]; if (!bp->pending) @@ -1266,7 +1286,7 @@ static void md_bitmap_set_pending(struct bitmap_counts *bitmap, sector_t offset) static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts *bitmap, sector_t offset, sector_t *blocks, - int create); + int create, spinlock_t *bmclock, int locktype); static void mddev_set_timeout(struct mddev *mddev, unsigned long timeout, bool force) @@ -1349,7 +1369,7 @@ void md_bitmap_daemon_work(struct mddev *mddev) * decrement and handle accordingly. */ counts = &bitmap->counts; - spin_lock_irq(&counts->lock); + write_lock_irq(&counts->mlock); nextpage = 0; for (j = 0; j < counts->chunks; j++) { bitmap_counter_t *bmc; @@ -1364,7 +1384,7 @@ void md_bitmap_daemon_work(struct mddev *mddev) counts->bp[j >> PAGE_COUNTER_SHIFT].pending = 0; } - bmc = md_bitmap_get_counter(counts, block, &blocks, 0); + bmc = md_bitmap_get_counter(counts, block, &blocks, 0, 0, 0); if (!bmc) { j |= PAGE_COUNTER_MASK; continue; @@ -1380,7 +1400,7 @@ void md_bitmap_daemon_work(struct mddev *mddev) bitmap->allclean = 0; } } - spin_unlock_irq(&counts->lock); + write_unlock_irq(&counts->mlock); md_bitmap_wait_writes(bitmap); /* Now start writeout on any page in NEEDWRITE that isn't DIRTY. @@ -1413,17 +1433,25 @@ void md_bitmap_daemon_work(struct mddev *mddev) static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts *bitmap, sector_t offset, sector_t *blocks, - int create) -__releases(bitmap->lock) -__acquires(bitmap->lock) + int create, spinlock_t *bmclock, int locktype) +__releases(bmclock) +__acquires(bmclock) +__releases(bitmap->mlock) +__acquires(bitmap->mlock) { /* If 'create', we might release the lock and reclaim it. * The lock must have been taken with interrupts enabled. * If !create, we don't release the lock. */ - sector_t chunk = offset >> bitmap->chunkshift; - unsigned long page = chunk >> PAGE_COUNTER_SHIFT; - unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT; + sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT); + sector_t totblocks = bitmap->chunks << (bitmap->chunkshift - (PAGE_SHIFT - SECTOR_SHIFT)); + unsigned long bits = totblocks ? fls((totblocks - 1)) : 0; + unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX << + (bits - (bitmap->chunkshift + SECTOR_SHIFT - PAGE_SHIFT))); + unsigned long cntid = blockno & mask; + unsigned long page = cntid >> PAGE_COUNTER_SHIFT; + unsigned long pageoff = (cntid & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT; + sector_t csize; int err; @@ -1435,7 +1463,7 @@ __acquires(bitmap->lock) */ return NULL; } - err = md_bitmap_checkpage(bitmap, page, create, 0); + err = md_bitmap_checkpage(bitmap, page, create, 0, bmclock, 1); if (bitmap->bp[page].hijacked || bitmap->bp[page].map == NULL) @@ -1461,6 +1489,28 @@ __acquires(bitmap->lock) &(bitmap->bp[page].map[pageoff]); } +/* set-association */ +static spinlock_t *md_bitmap_get_bmclock(struct bitmap_counts *bitmap, sector_t offset); + +static spinlock_t *md_bitmap_get_bmclock(struct bitmap_counts *bitmap, sector_t offset) +{ + sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT); + sector_t totblocks = bitmap->chunks << (bitmap->chunkshift - (PAGE_SHIFT - SECTOR_SHIFT)); + unsigned long bitscnt = totblocks ? fls((totblocks - 1)) : 0; + unsigned long maskcnt = ULONG_MAX << bitscnt | ~(ULONG_MAX << (bitscnt - + (bitmap->chunkshift + SECTOR_SHIFT - PAGE_SHIFT))); + unsigned long cntid = blockno & maskcnt; + + unsigned long totcnts = bitmap->chunks; + unsigned long bitslock = totcnts ? fls((totcnts - 1)) : 0; + unsigned long masklock = ULONG_MAX << bitslock | ~(ULONG_MAX << + (bitslock - BITMAP_COUNTER_LOCK_RATIO_SHIFT)); + unsigned long lockid = cntid & masklock; + + spinlock_t *bmclock = &(bitmap->bmclocks[lockid]); + return bmclock; +} + int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind) { if (!bitmap) @@ -1480,11 +1530,15 @@ int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long s while (sectors) { sector_t blocks; bitmap_counter_t *bmc; + spinlock_t *bmclock; - spin_lock_irq(&bitmap->counts.lock); - bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 1); + bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset); + read_lock(&bitmap->counts.mlock); + spin_lock_irq(bmclock); + bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 1, bmclock, 1); if (!bmc) { - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); return 0; } @@ -1496,7 +1550,8 @@ int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long s */ prepare_to_wait(&bitmap->overflow_wait, &__wait, TASK_UNINTERRUPTIBLE); - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); schedule(); finish_wait(&bitmap->overflow_wait, &__wait); continue; @@ -1513,7 +1568,8 @@ int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long s (*bmc)++; - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); offset += blocks; if (sectors > blocks) @@ -1542,11 +1598,15 @@ void md_bitmap_endwrite(struct bitmap *bitmap, sector_t offset, sector_t blocks; unsigned long flags; bitmap_counter_t *bmc; + spinlock_t *bmclock; - spin_lock_irqsave(&bitmap->counts.lock, flags); - bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 0); + bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset); + read_lock(&bitmap->counts.mlock); + spin_lock_irqsave(bmclock, flags); + bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 0, bmclock, 1); if (!bmc) { - spin_unlock_irqrestore(&bitmap->counts.lock, flags); + spin_unlock_irqrestore(bmclock, flags); + read_unlock(&bitmap->counts.mlock); return; } @@ -1568,7 +1628,8 @@ void md_bitmap_endwrite(struct bitmap *bitmap, sector_t offset, md_bitmap_set_pending(&bitmap->counts, offset); bitmap->allclean = 0; } - spin_unlock_irqrestore(&bitmap->counts.lock, flags); + spin_unlock_irqrestore(bmclock, flags); + read_unlock(&bitmap->counts.mlock); offset += blocks; if (sectors > blocks) sectors -= blocks; @@ -1582,13 +1643,16 @@ static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t int degraded) { bitmap_counter_t *bmc; + spinlock_t *bmclock; int rv; if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */ *blocks = 1024; return 1; /* always resync if no bitmap */ } - spin_lock_irq(&bitmap->counts.lock); - bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0); + bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset); + read_lock(&bitmap->counts.mlock); + spin_lock_irq(bmclock); + bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0, bmclock, 1); rv = 0; if (bmc) { /* locked */ @@ -1602,7 +1666,8 @@ static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t } } } - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); return rv; } @@ -1634,13 +1699,16 @@ void md_bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks { bitmap_counter_t *bmc; unsigned long flags; + spinlock_t *bmclock; if (bitmap == NULL) { *blocks = 1024; return; } - spin_lock_irqsave(&bitmap->counts.lock, flags); - bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0); + bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset); + read_lock(&bitmap->counts.mlock); + spin_lock_irqsave(bmclock, flags); + bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0, bmclock, 1); if (bmc == NULL) goto unlock; /* locked */ @@ -1657,7 +1725,8 @@ void md_bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks } } unlock: - spin_unlock_irqrestore(&bitmap->counts.lock, flags); + spin_unlock_irqrestore(bmclock, flags); + read_unlock(&bitmap->counts.mlock); } EXPORT_SYMBOL(md_bitmap_end_sync); @@ -1738,10 +1807,15 @@ static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, in sector_t secs; bitmap_counter_t *bmc; - spin_lock_irq(&bitmap->counts.lock); - bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs, 1); + spinlock_t *bmclock; + + bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset); + read_lock(&bitmap->counts.mlock); + spin_lock_irq(bmclock); + bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs, 1, bmclock, 1); if (!bmc) { - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); return; } if (!*bmc) { @@ -1752,7 +1826,8 @@ static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, in } if (needed) *bmc |= NEEDED_MASK; - spin_unlock_irq(&bitmap->counts.lock); + spin_unlock_irq(bmclock); + read_unlock(&bitmap->counts.mlock); } /* dirty the memory and file bits for bitmap chunks "s" to "e" */ @@ -1806,6 +1881,7 @@ void md_bitmap_free(struct bitmap *bitmap) { unsigned long k, pages; struct bitmap_page *bp; + spinlock_t *bmclocks; if (!bitmap) /* there was no bitmap */ return; @@ -1826,6 +1902,7 @@ void md_bitmap_free(struct bitmap *bitmap) bp = bitmap->counts.bp; pages = bitmap->counts.pages; + bmclocks = bitmap->counts.bmclocks; /* free all allocated memory */ @@ -1834,6 +1911,7 @@ void md_bitmap_free(struct bitmap *bitmap) if (bp[k].map && !bp[k].hijacked) kfree(bp[k].map); kfree(bp); + kfree(bmclocks); kfree(bitmap); } EXPORT_SYMBOL(md_bitmap_free); @@ -1900,7 +1978,9 @@ struct bitmap *md_bitmap_create(struct mddev *mddev, int slot) if (!bitmap) return ERR_PTR(-ENOMEM); - spin_lock_init(&bitmap->counts.lock); + /* initialize metadata lock */ + rwlock_init(&bitmap->counts.mlock); + atomic_set(&bitmap->pending_writes, 0); init_waitqueue_head(&bitmap->write_wait); init_waitqueue_head(&bitmap->overflow_wait); @@ -2143,6 +2223,8 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, int ret = 0; long pages; struct bitmap_page *new_bp; + spinlock_t *new_bmclocks; + int num_bmclocks, i; if (bitmap->storage.file && !init) { pr_info("md: cannot resize file-based bitmap\n"); @@ -2211,7 +2293,7 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, memcpy(page_address(store.sb_page), page_address(bitmap->storage.sb_page), sizeof(bitmap_super_t)); - spin_lock_irq(&bitmap->counts.lock); + write_lock_irq(&bitmap->counts.mlock); md_bitmap_file_unmap(&bitmap->storage); bitmap->storage = store; @@ -2227,18 +2309,28 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, blocks = min(old_counts.chunks << old_counts.chunkshift, chunks << chunkshift); + /* initialize bmc locks */ + num_bmclocks = DIV_ROUND_UP(chunks, BITMAP_COUNTER_LOCK_RATIO); + + new_bmclocks = kvcalloc(num_bmclocks, sizeof(*new_bmclocks), GFP_KERNEL); + bitmap->counts.bmclocks = new_bmclocks; + for (i = 0; i < num_bmclocks; ++i) { + spinlock_t *bmclock = &(bitmap->counts.bmclocks)[i]; + + spin_lock_init(bmclock); + } + /* For cluster raid, need to pre-allocate bitmap */ if (mddev_is_clustered(bitmap->mddev)) { unsigned long page; for (page = 0; page < pages; page++) { - ret = md_bitmap_checkpage(&bitmap->counts, page, 1, 1); + ret = md_bitmap_checkpage(&bitmap->counts, page, 1, 1, 0, 0); if (ret) { unsigned long k; /* deallocate the page memory */ - for (k = 0; k < page; k++) { + for (k = 0; k < page; k++) kfree(new_bp[k].map); - } kfree(new_bp); /* restore some fields from old_counts */ @@ -2261,11 +2353,12 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, bitmap_counter_t *bmc_old, *bmc_new; int set; - bmc_old = md_bitmap_get_counter(&old_counts, block, &old_blocks, 0); + bmc_old = md_bitmap_get_counter(&old_counts, block, &old_blocks, 0, 0, 0); set = bmc_old && NEEDED(*bmc_old); if (set) { - bmc_new = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1); + bmc_new = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, + 1, 0, 0); if (bmc_new) { if (*bmc_new == 0) { /* need to set on-disk bits too. */ @@ -2301,7 +2394,7 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, int i; while (block < (chunks << chunkshift)) { bitmap_counter_t *bmc; - bmc = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1); + bmc = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1, 0, 0); if (bmc) { /* new space. It needs to be resynced, so * we set NEEDED_MASK. @@ -2317,7 +2410,7 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks, for (i = 0; i < bitmap->storage.file_pages; i++) set_page_attr(bitmap, i, BITMAP_PAGE_DIRTY); } - spin_unlock_irq(&bitmap->counts.lock); + write_unlock_irq(&bitmap->counts.mlock); if (!init) { md_bitmap_unplug(bitmap); diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h index bb9eb418780a..1b9c36bb73ed 100644 --- a/drivers/md/md-bitmap.h +++ b/drivers/md/md-bitmap.h @@ -2,7 +2,9 @@ /* * bitmap.h: Copyright (C) Peter T. Breuer (ptb@xxxxxxxxxx) 2003 * - * additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc. + * additions: + * Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc. + * Copyright (C) 2022-2023, Shushu Yi (firnyee@xxxxxxxxx) */ #ifndef BITMAP_H #define BITMAP_H 1 @@ -103,6 +105,9 @@ typedef __u16 bitmap_counter_t; #define PAGE_COUNTER_MASK (PAGE_COUNTER_RATIO - 1) #define BITMAP_BLOCK_SHIFT 9 +/* how many counters share the same bmclock? */ +#define BITMAP_COUNTER_LOCK_RATIO_SHIFT 0 +#define BITMAP_COUNTER_LOCK_RATIO (1 << BITMAP_COUNTER_LOCK_RATIO_SHIFT) #endif @@ -116,7 +121,7 @@ typedef __u16 bitmap_counter_t; enum bitmap_state { BITMAP_STALE = 1, /* the bitmap file is out of date or had -EIO */ BITMAP_WRITE_ERROR = 2, /* A write error has occurred */ - BITMAP_HOSTENDIAN =15, + BITMAP_HOSTENDIAN = 15, }; /* the superblock at the front of the bitmap file -- little endian */ @@ -180,7 +185,8 @@ struct bitmap_page { struct bitmap { struct bitmap_counts { - spinlock_t lock; + rwlock_t mlock; /* lock for metadata */ + spinlock_t *bmclocks; /* locks for bmc */ struct bitmap_page *bp; unsigned long pages; /* total number of pages * in the bitmap */ -- 2.34.1
