[PATCH v5] dm crypt: scale to multiple CPUs

From: Milan Broz
Date: Fri Nov 12 2010 - 13:52:12 EST

Hi,
finally I found some time and tried to fix that Andi's dm-crypt patch
to not break stacking.

Here is what I have:
- it still keeps two per device threads, with WQ_NON_REENTRANT set
- only crypt thread is cpu intensive

There is for sure space for additional optimisations (that reentrant flags
must limit it) but I think it fixes exactly the same problem without breaking
other things.

I got very similar results with this patch compared to original Andi's v3 patch.

All stacking and async crypto problems are gone, even 20 dm-crypt devices
stacked works for me now.

Some numbers - really stupid test, run 4 threads on 2.6.37-rc1+ 2xdualcore CPU
with aes-xts-plain64/256bit encrypted block device like this

fio --rw=$1 --size=1G --bsrange=1k-128k --filename=$2 --name=1 --name=2 --name=3 --name=4

(similar is cbs-ESSIV, but I want to test just per-cpu worker changes)

values below are just aggregated numbers (aggrb) from fio output.

1) device backed by dm-zero (reads/writes -> noop)
(so there no real device, it should measure just dm-crypt performance)

old code new (per cpu)
zero-read 117205KB/s 193866KB/s
zero-write 160572KB/s 324109KB/s
zero-randread 137829KB/s 180477KB/s
zero-randwrite 56088KB/s 206158KB/s
zero-rw READS 39192KB/s 52667KB/s
zero-rw WRITES 39534KB/s 52746KB/s
zero-randrw READS 43220KB/s 103868KB/s
zero-randrw WRITES 43322KB/s 104192KB/s

2) and the same test backed by MD/RAID0
(no tuning here, drives use CFQ, but I have no better
machine for now)

disk-read 100598KB/s 141802KB/s
disk-write 78848KB/s 178102KB/s
disk-randread 51148KB/s 49378KB/s
disk-randwrite 32679KB/s 49560KB/s
disk-rw READS 36812KB/s 40575KB/s
disk-rw WRITES 36506KB/s 40552KB/s
disk-randrw READS 19426KB/s 24603KB/s
disk-randrw WRITES 19402KB/s 24479KB/s


Andi, is this version ok for you?

So we can move forward, and finally include this.
(There should be some other optimisations but I would like
to commit this first and all changes do as following patches.)

Thanks,
Milan

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index d5b0e4c..b4dac68 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -18,6 +18,7 @@
#include <linux/crypto.h>
#include <linux/workqueue.h>
#include <linux/backing-dev.h>
+#include <linux/percpu.h>
#include <asm/atomic.h>
#include <linux/scatterlist.h>
#include <asm/page.h>
@@ -77,7 +78,6 @@ struct crypt_iv_operations {
};

struct iv_essiv_private {
- struct crypto_cipher *tfm;
struct crypto_hash *hash_tfm;
u8 *salt;
};
@@ -91,6 +91,20 @@ struct iv_benbi_private {
* and encrypts / decrypts at the same time.
*/
enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
+
+/* Duplicated per CPU state for cipher */
+struct crypt_cpu {
+ struct ablkcipher_request *req;
+ struct crypto_ablkcipher *tfm;
+
+ /* ESSIV: struct crypto_cipher *essiv_tfm */
+ void *iv_private;
+};
+
+/*
+ * The fields in here must be read only after initialization,
+ * changing state should be in crypt_cpu.
+ */
struct crypt_config {
struct dm_dev *dev;
sector_t start;
@@ -119,6 +133,12 @@ struct crypt_config {
unsigned int iv_size;

/*
+ * Duplicated per cpu state. Access through
+ * per_cpu_ptr() only.
+ */
+ struct crypt_cpu __percpu *cpu;
+
+ /*
* Layout of each crypto request:
*
* struct ablkcipher_request
@@ -132,9 +152,7 @@ struct crypt_config {
* correctly aligned.
*/
unsigned int dmreq_start;
- struct ablkcipher_request *req;

- struct crypto_ablkcipher *tfm;
unsigned long flags;
unsigned int key_size;
u8 key[0];
@@ -149,6 +167,20 @@ static struct kmem_cache *_crypt_io_pool;
static void clone_init(struct dm_crypt_io *, struct bio *);
static void kcryptd_queue_crypt(struct dm_crypt_io *io);

+static struct crypt_cpu *crypt_me(struct crypt_config *cc)
+{
+ return this_cpu_ptr(cc->cpu);
+}
+
+/* Use this for cipher attributes that are the same for all cpus */
+static struct crypto_ablkcipher *any_tfm(struct crypt_config *cc)
+{
+ struct crypto_ablkcipher *tfm;
+ /* cpu doesn't matter, output is always the same */
+ tfm = __this_cpu_ptr(cc->cpu)->tfm;
+ return tfm;
+}
+
/*
* Different IV generation algorithms:
*
@@ -195,7 +227,9 @@ static int crypt_iv_essiv_init(struct crypt_config *cc)
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
struct hash_desc desc;
struct scatterlist sg;
- int err;
+ struct crypt_cpu *cs;
+ struct crypto_cipher *essiv_tfm;
+ int err, n, cpu;

sg_init_one(&sg, cc->key, cc->key_size);
desc.tfm = essiv->hash_tfm;
@@ -205,8 +239,19 @@ static int crypt_iv_essiv_init(struct crypt_config *cc)
if (err)
return err;

- return crypto_cipher_setkey(essiv->tfm, essiv->salt,
+ for_each_possible_cpu (cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ essiv_tfm = cs->iv_private,
+
+ n = crypto_cipher_setkey(essiv_tfm, essiv->salt,
crypto_hash_digestsize(essiv->hash_tfm));
+ if (n) {
+ err = n;
+ break;
+ }
+ }
+
+ return err;
}

/* Wipe salt and reset key derived from volume key */
@@ -214,24 +259,75 @@ static int crypt_iv_essiv_wipe(struct crypt_config *cc)
{
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
unsigned salt_size = crypto_hash_digestsize(essiv->hash_tfm);
+ struct crypt_cpu *cs;
+ struct crypto_cipher *essiv_tfm;
+ int cpu, err, n;

memset(essiv->salt, 0, salt_size);

- return crypto_cipher_setkey(essiv->tfm, essiv->salt, salt_size);
+ err = 0;
+ for_each_possible_cpu (cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ essiv_tfm = cs->iv_private;
+ n = crypto_cipher_setkey(essiv_tfm, essiv->salt, salt_size);
+ if (n)
+ err = n;
+ }
+ return err;
+}
+
+/* Set up per cpu cipher state */
+static struct crypto_cipher *setup_essiv_cpu(struct crypt_config *cc,
+ struct dm_target *ti,
+ u8 *salt, unsigned saltsize)
+{
+ struct crypto_cipher *essiv_tfm;
+ int err;
+
+ /* Setup the essiv_tfm with the given salt */
+ essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(essiv_tfm)) {
+ ti->error = "Error allocating crypto tfm for ESSIV";
+ return essiv_tfm;
+ }
+
+ if (crypto_cipher_blocksize(essiv_tfm) !=
+ crypto_ablkcipher_ivsize(any_tfm(cc))) {
+ ti->error = "Block size of ESSIV cipher does "
+ "not match IV size of block cipher";
+ crypto_free_cipher(essiv_tfm);
+ return ERR_PTR(-EINVAL);
+ }
+ err = crypto_cipher_setkey(essiv_tfm, salt, saltsize);
+ if (err) {
+ ti->error = "Failed to set key for ESSIV cipher";
+ crypto_free_cipher(essiv_tfm);
+ return ERR_PTR(err);
+ }
+
+ return essiv_tfm;
}

static void crypt_iv_essiv_dtr(struct crypt_config *cc)
{
+ int cpu;
+ struct crypt_cpu *cs;
+ struct crypto_cipher *essiv_tfm;
struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;

- crypto_free_cipher(essiv->tfm);
- essiv->tfm = NULL;
-
crypto_free_hash(essiv->hash_tfm);
essiv->hash_tfm = NULL;

kzfree(essiv->salt);
essiv->salt = NULL;
+
+ for_each_possible_cpu (cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ essiv_tfm = cs->iv_private;
+ if (essiv_tfm)
+ crypto_free_cipher(essiv_tfm);
+ cs->iv_private = NULL;
+ }
}

static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
@@ -240,7 +336,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
struct crypto_cipher *essiv_tfm = NULL;
struct crypto_hash *hash_tfm = NULL;
u8 *salt = NULL;
- int err;
+ int err, cpu;

if (!opts) {
ti->error = "Digest algorithm missing for ESSIV mode";
@@ -262,30 +358,21 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
goto bad;
}

- /* Allocate essiv_tfm */
- essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(essiv_tfm)) {
- ti->error = "Error allocating crypto tfm for ESSIV";
- err = PTR_ERR(essiv_tfm);
- goto bad;
- }
- if (crypto_cipher_blocksize(essiv_tfm) !=
- crypto_ablkcipher_ivsize(cc->tfm)) {
- ti->error = "Block size of ESSIV cipher does "
- "not match IV size of block cipher";
- err = -EINVAL;
- goto bad;
- }
-
cc->iv_gen_private.essiv.salt = salt;
- cc->iv_gen_private.essiv.tfm = essiv_tfm;
cc->iv_gen_private.essiv.hash_tfm = hash_tfm;

+ for_each_possible_cpu (cpu) {
+ essiv_tfm = setup_essiv_cpu(cc, ti, salt,
+ crypto_hash_digestsize(hash_tfm));
+ if (IS_ERR(essiv_tfm)) {
+ crypt_iv_essiv_dtr(cc);
+ return PTR_ERR(essiv_tfm);
+ }
+ per_cpu_ptr(cc->cpu, cpu)->iv_private = essiv_tfm;
+ }
return 0;

bad:
- if (essiv_tfm && !IS_ERR(essiv_tfm))
- crypto_free_cipher(essiv_tfm);
if (hash_tfm && !IS_ERR(hash_tfm))
crypto_free_hash(hash_tfm);
kfree(salt);
@@ -294,16 +381,18 @@ bad:

static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
+ struct crypto_cipher *essiv_tfm = crypt_me(cc)->iv_private;
+
memset(iv, 0, cc->iv_size);
*(u64 *)iv = cpu_to_le64(sector);
- crypto_cipher_encrypt_one(cc->iv_gen_private.essiv.tfm, iv, iv);
+ crypto_cipher_encrypt_one(essiv_tfm, iv, iv);
return 0;
}

static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
const char *opts)
{
- unsigned bs = crypto_ablkcipher_blocksize(cc->tfm);
+ unsigned bs = crypto_ablkcipher_blocksize(any_tfm(cc));
int log = ilog2(bs);

/* we need to calculate how far we must shift the sector count
@@ -412,7 +501,7 @@ static int crypt_convert_block(struct crypt_config *cc,

dmreq = dmreq_of_req(cc, req);
iv = (u8 *)ALIGN((unsigned long)(dmreq + 1),
- crypto_ablkcipher_alignmask(cc->tfm) + 1);
+ crypto_ablkcipher_alignmask(any_tfm(cc)) + 1);

dmreq->ctx = ctx;
sg_init_table(&dmreq->sg_in, 1);
@@ -457,13 +546,14 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
static void crypt_alloc_req(struct crypt_config *cc,
struct convert_context *ctx)
{
- if (!cc->req)
- cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);
- ablkcipher_request_set_tfm(cc->req, cc->tfm);
- ablkcipher_request_set_callback(cc->req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ struct crypt_cpu *cs = crypt_me(cc);
+ if (!cs->req)
+ cs->req = mempool_alloc(cc->req_pool, GFP_NOIO);
+ ablkcipher_request_set_tfm(cs->req, cs->tfm);
+ ablkcipher_request_set_callback(cs->req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
kcryptd_async_done,
- dmreq_of_req(cc, cc->req));
+ dmreq_of_req(cc, cs->req));
}

/*
@@ -472,6 +562,7 @@ static void crypt_alloc_req(struct crypt_config *cc,
static int crypt_convert(struct crypt_config *cc,
struct convert_context *ctx)
{
+ struct crypt_cpu *cs = crypt_me(cc);
int r;

atomic_set(&ctx->pending, 1);
@@ -483,7 +574,7 @@ static int crypt_convert(struct crypt_config *cc,

atomic_inc(&ctx->pending);

- r = crypt_convert_block(cc, ctx, cc->req);
+ r = crypt_convert_block(cc, ctx, cs->req);

switch (r) {
/* async */
@@ -492,7 +583,7 @@ static int crypt_convert(struct crypt_config *cc,
INIT_COMPLETION(ctx->restart);
/* fall through*/
case -EINPROGRESS:
- cc->req = NULL;
+ cs->req = NULL;
ctx->sector++;
continue;

@@ -651,6 +742,9 @@ static void crypt_dec_pending(struct dm_crypt_io *io)
* They must be separated as otherwise the final stages could be
* starved by new requests which can block in the first stages due
* to memory allocation.
+ *
+ * The work is done per CPU global for all dmcrypt instances.
+ * They should not depend on each other and do not block.
*/
static void crypt_endio(struct bio *clone, int error)
{
@@ -971,6 +1065,22 @@ static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
}
}

+static int crypt_setkey_allcpus(struct crypt_config *cc)
+{
+ struct crypt_cpu *cs;
+ int cpu, n, err;
+
+ err = 0;
+ for_each_possible_cpu(cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ n = crypto_ablkcipher_setkey(cs->tfm, cc->key, cc->key_size);
+ if (n)
+ err = n;
+ }
+ return err;
+}
+
+
static int crypt_set_key(struct crypt_config *cc, char *key)
{
unsigned key_size = strlen(key) >> 1;
@@ -986,19 +1096,35 @@ static int crypt_set_key(struct crypt_config *cc, char *key)

set_bit(DM_CRYPT_KEY_VALID, &cc->flags);

- return crypto_ablkcipher_setkey(cc->tfm, cc->key, cc->key_size);
+ return crypt_setkey_allcpus(cc);
}

static int crypt_wipe_key(struct crypt_config *cc)
{
clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
memset(&cc->key, 0, cc->key_size * sizeof(u8));
- return crypto_ablkcipher_setkey(cc->tfm, cc->key, cc->key_size);
+ return crypt_setkey_allcpus(cc);
+}
+
+static void crypt_dtr_cpus(struct crypt_config *cc)
+{
+ struct crypt_cpu *cs;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ if (cs->tfm) {
+ crypto_free_ablkcipher(cs->tfm);
+ cs->tfm = NULL;
+ }
+ }
}

static void crypt_dtr(struct dm_target *ti)
{
struct crypt_config *cc = ti->private;
+ struct crypt_cpu *cs;
+ int cpu;

ti->private = NULL;

@@ -1010,6 +1136,12 @@ static void crypt_dtr(struct dm_target *ti)
if (cc->crypt_queue)
destroy_workqueue(cc->crypt_queue);

+ for_each_possible_cpu(cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ if (cs->req)
+ mempool_free(cs->req, cc->req_pool);
+ }
+
if (cc->bs)
bioset_free(cc->bs);

@@ -1023,12 +1155,14 @@ static void crypt_dtr(struct dm_target *ti)
if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
cc->iv_gen_ops->dtr(cc);

- if (cc->tfm && !IS_ERR(cc->tfm))
- crypto_free_ablkcipher(cc->tfm);
-
if (cc->dev)
dm_put_device(ti, cc->dev);

+ crypt_dtr_cpus(cc);
+
+ if (cc->cpu)
+ free_percpu(cc->cpu);
+
kzfree(cc->cipher);
kzfree(cc->cipher_mode);

@@ -1040,9 +1174,10 @@ static int crypt_ctr_cipher(struct dm_target *ti,
char *cipher_in, char *key)
{
struct crypt_config *cc = ti->private;
+ struct crypto_ablkcipher *tfm;
char *tmp, *cipher, *chainmode, *ivmode, *ivopts;
char *cipher_api = NULL;
- int ret = -EINVAL;
+ int cpu, ret = -EINVAL;

/* Convert to crypto api definition? */
if (strchr(cipher_in, '(')) {
@@ -1074,6 +1209,12 @@ static int crypt_ctr_cipher(struct dm_target *ti,
if (tmp)
DMWARN("Ignoring unexpected additional cipher options");

+ cc->cpu = alloc_percpu(struct crypt_cpu);
+ if (!cc->cpu) {
+ ti->error = "Cannot allocate per cpu state";
+ goto bad_mem;
+ }
+
/* Compatibility mode for old dm-crypt mappings */
if (!chainmode || (!strcmp(chainmode, "plain") && !ivmode)) {
kfree(cc->cipher_mode);
@@ -1099,12 +1240,16 @@ static int crypt_ctr_cipher(struct dm_target *ti,
}

/* Allocate cipher */
- cc->tfm = crypto_alloc_ablkcipher(cipher_api, 0, 0);
- if (IS_ERR(cc->tfm)) {
- ret = PTR_ERR(cc->tfm);
- ti->error = "Error allocating crypto tfm";
- goto bad;
- }
+ for_each_possible_cpu (cpu) {
+ tfm = crypto_alloc_ablkcipher(cipher_api, 0, 0);
+ if (IS_ERR(tfm)) {
+ ret = PTR_ERR(tfm);
+ ti->error = "Error allocating crypto tfm";
+ goto bad;
+ }
+ per_cpu_ptr(cc->cpu, cpu)->tfm = tfm;
+ }
+ tfm = any_tfm(cc);

/* Initialize and set key */
ret = crypt_set_key(cc, key);
@@ -1114,7 +1259,7 @@ static int crypt_ctr_cipher(struct dm_target *ti,
}

/* Initialize IV */
- cc->iv_size = crypto_ablkcipher_ivsize(cc->tfm);
+ cc->iv_size = crypto_ablkcipher_ivsize(tfm);
if (cc->iv_size)
/* at least a 64 bit sector number should fit in our buffer */
cc->iv_size = max(cc->iv_size,
@@ -1178,9 +1323,10 @@ bad_mem:
static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct crypt_config *cc;
+ struct crypt_cpu *cs;
unsigned int key_size;
unsigned long long tmpll;
- int ret;
+ int ret, cpu;

if (argc != 5) {
ti->error = "Not enough arguments";
@@ -1208,9 +1354,9 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}

cc->dmreq_start = sizeof(struct ablkcipher_request);
- cc->dmreq_start += crypto_ablkcipher_reqsize(cc->tfm);
+ cc->dmreq_start += crypto_ablkcipher_reqsize(any_tfm(cc));
cc->dmreq_start = ALIGN(cc->dmreq_start, crypto_tfm_ctx_alignment());
- cc->dmreq_start += crypto_ablkcipher_alignmask(cc->tfm) &
+ cc->dmreq_start += crypto_ablkcipher_alignmask(any_tfm(cc)) &
~(crypto_tfm_ctx_alignment() - 1);

cc->req_pool = mempool_create_kmalloc_pool(MIN_IOS, cc->dmreq_start +
@@ -1219,7 +1365,6 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->error = "Cannot allocate crypt request mempool";
goto bad;
}
- cc->req = NULL;

cc->page_pool = mempool_create_page_pool(MIN_POOL_PAGES, 0);
if (!cc->page_pool) {
@@ -1233,6 +1378,14 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad;
}

+ for_each_possible_cpu(cpu) {
+ cs = per_cpu_ptr(cc->cpu, cpu);
+ if (crypto_ablkcipher_setkey(cs->tfm, cc->key, key_size) < 0) {
+ ti->error = "Error setting key";
+ goto bad;
+ }
+ }
+
ret = -EINVAL;
if (sscanf(argv[2], "%llu", &tmpll) != 1) {
ti->error = "Invalid iv_offset sector";
@@ -1252,13 +1405,20 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
cc->start = tmpll;

ret = -ENOMEM;
- cc->io_queue = create_singlethread_workqueue("kcryptd_io");
+ cc->io_queue = alloc_workqueue("kcryptd_io",
+ WQ_NON_REENTRANT|
+ WQ_MEM_RECLAIM,
+ 1);
if (!cc->io_queue) {
ti->error = "Couldn't create kcryptd io queue";
goto bad;
}

- cc->crypt_queue = create_singlethread_workqueue("kcryptd");
+ cc->crypt_queue = alloc_workqueue("kcryptd",
+ WQ_NON_REENTRANT|
+ WQ_CPU_INTENSIVE|
+ WQ_MEM_RECLAIM,
+ 1);
if (!cc->crypt_queue) {
ti->error = "Couldn't create kcryptd queue";
goto bad;


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