When using dm-crypt for full disk encryption, dm-crypt would allocate
an out bio and allocate the same amount of pages as in bio for
encryption. It currently allocates one page at a time in a loop. This
is not efficient. So using mempool page bulk allocator instead of
allocating one page at a time.
The mempool page bulk allocator would improve the IOPS with 1M I/O
by approxiamately 6%. The test is done on a VM with 80 vCPU and
64GB memory with an encrypted ram device (the impact from storage
hardware could be minimized so that we could benchmark the dm-crypt
layer more accurately).
Before the patch:
Jobs: 1 (f=1): [w(1)][100.0%][r=0KiB/s,w=402MiB/s][r=0,w=402 IOPS][eta 00m:00s]
crypt: (groupid=0, jobs=1): err= 0: pid=233950: Thu Sep 15 16:23:10 2022
write: IOPS=402, BW=403MiB/s (423MB/s)(23.6GiB/60002msec)
slat (usec): min=2425, max=3819, avg=2480.84, stdev=34.00
clat (usec): min=7, max=165751, avg=156398.72, stdev=4691.03
lat (msec): min=2, max=168, avg=158.88, stdev= 4.69
clat percentiles (msec):
| 1.00th=[ 157], 5.00th=[ 157], 10.00th=[ 157], 20.00th=[ 157],
| 30.00th=[ 157], 40.00th=[ 157], 50.00th=[ 157], 60.00th=[ 157],
| 70.00th=[ 157], 80.00th=[ 157], 90.00th=[ 157], 95.00th=[ 157],
| 99.00th=[ 159], 99.50th=[ 159], 99.90th=[ 165], 99.95th=[ 165],
| 99.99th=[ 167]
bw ( KiB/s): min=405504, max=413696, per=99.71%, avg=411845.53,
stdev=1155.04, samples=120
iops : min= 396, max= 404, avg=402.17, stdev= 1.15, samples=120
lat (usec) : 10=0.01%
lat (msec) : 4=0.01%, 10=0.01%, 20=0.02%, 50=0.05%, 100=0.08%
lat (msec) : 250=100.09%
cpu : usr=3.74%, sys=95.66%, ctx=27, majf=0, minf=4
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=103.1%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
issued rwts: total=0,24138,0,0 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=64
Run status group 0 (all jobs):
WRITE: bw=403MiB/s (423MB/s), 403MiB/s-403MiB/s (423MB/s-423MB/s), io=23.6GiB
(25.4GB), run=60002-60002msec
After the patch:
Jobs: 1 (f=1): [w(1)][100.0%][r=0KiB/s,w=430MiB/s][r=0,w=430 IOPS][eta 00m:00s]
crypt: (groupid=0, jobs=1): err= 0: pid=288730: Thu Sep 15 16:25:39 2022
write: IOPS=430, BW=431MiB/s (452MB/s)(25.3GiB/60002msec)
slat (usec): min=2253, max=3213, avg=2319.49, stdev=34.29
clat (usec): min=6, max=149337, avg=146257.68, stdev=4239.52
lat (msec): min=2, max=151, avg=148.58, stdev= 4.24
clat percentiles (msec):
| 1.00th=[ 146], 5.00th=[ 146], 10.00th=[ 146], 20.00th=[ 146],
| 30.00th=[ 146], 40.00th=[ 146], 50.00th=[ 146], 60.00th=[ 146],
| 70.00th=[ 146], 80.00th=[ 146], 90.00th=[ 148], 95.00th=[ 148],
| 99.00th=[ 148], 99.50th=[ 148], 99.90th=[ 150], 99.95th=[ 150],
| 99.99th=[ 150]
bw ( KiB/s): min=438272, max=442368, per=99.73%, avg=440463.57,
stdev=1305.60, samples=120
iops : min= 428, max= 432, avg=430.12, stdev= 1.28, samples=120
lat (usec) : 10=0.01%
lat (msec) : 4=0.01%, 10=0.01%, 20=0.02%, 50=0.05%, 100=0.09%
lat (msec) : 250=100.07%
cpu : usr=3.78%, sys=95.37%, ctx=12778, majf=0, minf=4
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=103.1%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
issued rwts: total=0,25814,0,0 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=64
Run status group 0 (all jobs):
WRITE: bw=431MiB/s (452MB/s), 431MiB/s-431MiB/s (452MB/s-452MB/s), io=25.3GiB
(27.1GB), run=60002-60002msec
The function tracing also shows the time consumed by page allocations is
reduced significantly. The test allocated 1M (256 pages) bio in the same
environment.
Before the patch:
It took approximately 600us by excluding the bio_add_page() calls.
2720.630754 | 56) xfs_io-38859 | 2.571 us | mempool_alloc();
2720.630757 | 56) xfs_io-38859 | 0.937 us | bio_add_page();
2720.630758 | 56) xfs_io-38859 | 1.772 us | mempool_alloc();
2720.630760 | 56) xfs_io-38859 | 0.852 us | bio_add_page();
….
2720.631559 | 56) xfs_io-38859 | 2.058 us | mempool_alloc();
2720.631561 | 56) xfs_io-38859 | 0.717 us | bio_add_page();
2720.631562 | 56) xfs_io-38859 | 2.014 us | mempool_alloc();
2720.631564 | 56) xfs_io-38859 | 0.620 us | bio_add_page();
After the patch:
It took approxiamately 30us.
11564.266385 | 22) xfs_io-136183 | + 30.551 us | __alloc_pages_bulk();
Page allocations overhead is around 6% (600us/9853us) in dm-crypt layer shown by
function trace. The data also matches the IOPS data shown by fio.
And the benchmark with 4K size I/O doesn't show measurable regression.
Signed-off-by: Yang Shi <[email protected]>
---
drivers/md/dm-crypt.c | 70 +++++++++++++++++++++++++------------------
1 file changed, 41 insertions(+), 29 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 85ac1f9b37ae..c86bd4af4d75 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1673,34 +1673,37 @@ static struct bio *crypt_alloc_buffer(struct
dm_crypt_io *io, unsigned size)
struct bio *clone;
unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
gfp_t gfp_mask = GFP_NOWAIT | __GFP_HIGHMEM;
- unsigned i, len, remaining_size;
+ unsigned len;
struct page *page;
-
-retry:
- if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
- mutex_lock(&cc->bio_alloc_lock);
+ LIST_HEAD(page_list);
clone = bio_alloc_bioset(cc->dev->bdev, nr_iovecs, io->base_bio->bi_opf,
GFP_NOIO, &cc->bs);
clone->bi_private = io;
clone->bi_end_io = crypt_endio;
- remaining_size = size;
+retry:
+ if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
+ mutex_lock(&cc->bio_alloc_lock);
- for (i = 0; i < nr_iovecs; i++) {
- page = mempool_alloc(&cc->page_pool, gfp_mask);
- if (!page) {
- crypt_free_buffer_pages(cc, clone);
- bio_put(clone);
- gfp_mask |= __GFP_DIRECT_RECLAIM;
- goto retry;
+ if (mempool_alloc_pages_bulk_list(&cc->page_pool, gfp_mask, nr_iovecs,
+ &page_list)) {
+ while (!list_empty(&page_list)) {
+ page = lru_to_page(&page_list);
+ list_del_init(&page->lru);
+ len = (size > PAGE_SIZE) ? PAGE_SIZE : size;
+ bio_add_page(clone, page, len, 0);
+ size -= len;
+ }
+ } else {
+ while (!list_empty(&page_list)) {
+ page = lru_to_page(&page_list);
+ list_del_init(&page->lru);
+ mempool_free(page, &cc->page_pool);
}
- len = (remaining_size > PAGE_SIZE) ? PAGE_SIZE : remaining_size;
-
- bio_add_page(clone, page, len, 0);
-
- remaining_size -= len;
+ gfp_mask |= __GFP_DIRECT_RECLAIM;
+ goto retry;
}
/* Allocate space for integrity tags */
@@ -2654,10 +2657,13 @@ static void crypt_calculate_pages_per_client(void)
dm_crypt_pages_per_client = pages;
}
-static void *crypt_page_alloc(gfp_t gfp_mask, void *pool_data)
+static unsigned int crypt_alloc_pages_bulk(gfp_t gfp_mask, unsigned int nr,
+ void *pool_data,
+ struct list_head *page_list,
+ struct page **page_array)
{
struct crypt_config *cc = pool_data;
- struct page *page;
+ unsigned int ret;
/*
* Note, percpu_counter_read_positive() may over (and under) estimate
@@ -2666,13 +2672,13 @@ static void *crypt_page_alloc(gfp_t gfp_mask, void
*pool_data)
*/
if (unlikely(percpu_counter_read_positive(&cc->n_allocated_pages) >=
dm_crypt_pages_per_client) &&
likely(gfp_mask & __GFP_NORETRY))
- return NULL;
+ return 0;
+
+ ret = alloc_pages_bulk_list(gfp_mask, nr, page_list);
- page = alloc_page(gfp_mask);
- if (likely(page != NULL))
- percpu_counter_add(&cc->n_allocated_pages, 1);
+ percpu_counter_add(&cc->n_allocated_pages, ret);
- return page;
+ return ret;
}
static void crypt_page_free(void *page, void *pool_data)
@@ -2704,13 +2710,17 @@ static void crypt_dtr(struct dm_target *ti)
bioset_exit(&cc->bs);
+ /*
+ * With mempool bulk allocator the pages in the pool are not
+ * counted in n_allocated_pages.
+ */
+ WARN_ON(percpu_counter_sum(&cc->n_allocated_pages) != 0);
+ percpu_counter_destroy(&cc->n_allocated_pages);
+
mempool_exit(&cc->page_pool);
mempool_exit(&cc->req_pool);
mempool_exit(&cc->tag_pool);
- WARN_ON(percpu_counter_sum(&cc->n_allocated_pages) != 0);
- percpu_counter_destroy(&cc->n_allocated_pages);
-
if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
cc->iv_gen_ops->dtr(cc);
@@ -3250,7 +3260,9 @@ static int crypt_ctr(struct dm_target *ti, unsigned int
argc, char **argv)
ALIGN(sizeof(struct dm_crypt_io) + cc->dmreq_start +
additional_req_size,
ARCH_KMALLOC_MINALIGN);
- ret = mempool_init(&cc->page_pool, BIO_MAX_VECS, crypt_page_alloc,
crypt_page_free, cc);
+ ret = mempool_init_pages_bulk(&cc->page_pool, BIO_MAX_VECS,
+ crypt_alloc_pages_bulk, crypt_page_free,
+ cc);
if (ret) {
ti->error = "Cannot allocate page mempool";
goto bad;
--
2.26.3
--
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