[PATCHv8 4/6] zram: add multi stream functionality
From: Sergey Senozhatsky
Date: Wed Feb 26 2014 - 07:32:01 EST
This patch implements multi stream compression support.
Introduce struct zcomp_strm_multi and a set of functions to manage
zcomp_strm stream access. zcomp_strm_multi has a list of idle zcomp_strm
structs, spinlock to protect idle list and wait queue, making it possible
to perform parallel compressions.
The following set of functions added:
- zcomp_strm_multi_get()/zcomp_strm_multi_put()
get and put compression stream, implement required locking
- zcomp_strm_multi_create()/zcomp_strm_multi_destroy()
create and destroy zcomp_strm_multi
zcomp ->strm_get() and ->strm_put() callbacks are set during initialisation
to zcomp_strm_multi_get()/zcomp_strm_multi_put() correspondingly.
Each time zcomp issues a zcomp_strm_multi_get() call, the following set of
operations performed:
- spin lock strm_lock
- if idle list is not empty, remove zcomp_strm from idle list, spin
unlock and return zcomp stream pointer to caller
- if idle list is empty, current adds itself to wait queue. it will be
awaken by zcomp_strm_multi_put() caller.
zcomp_strm_multi_put():
- spin lock strm_lock
- add zcomp stream to idle list
- spin unlock, wake up sleeper
Minchan Kim reported that spinlock-based locking scheme has demonstrated a
severe perfomance regression for single compression stream case, comparing
to mutex-based (see https://lkml.org/lkml/2014/2/18/16)
base spinlock mutex
==Initial write ==Initial write ==Initial write
records: 5 records: 5 records: 5
avg: 1642424.35 avg: 699610.40 avg: 1655583.71
std: 39890.95(2.43%) std: 232014.19(33.16%) std: 52293.96
max: 1690170.94 max: 1163473.45 max: 1697164.75
min: 1568669.52 min: 573429.88 min: 1553410.23
==Rewrite ==Rewrite ==Rewrite
records: 5 records: 5 records: 5
avg: 1611775.39 avg: 501406.64 avg: 1684419.11
std: 17144.58(1.06%) std: 15354.41(3.06%) std: 18367.42
max: 1641800.95 max: 531356.78 max: 1706445.84
min: 1593515.27 min: 488817.78 min: 1655335.73
When only one compression stream available, mutex with spin on owner tends
to perform much better than frequent wait_event()/wake_up(). This is why
single stream implemented as a special case with mutex locking.
Introduce zram device attribute max_comp_streams to show and store current
zcomp's max number of zcomp streams (max_strm) and extend zcomp's
zcomp_create() with `max_strm' parameter. `max_strm' limits the number of
zcomp_strm structs in compression backend's idle list (max_comp_streams).
max_comp_streams used during initialisation as follows:
-- passing to zcomp_create() max_strm equals to 1 will initialise zcomp
using single compression stream zcomp_strm_single (mutex-based locking).
-- passing to zcomp_create() max_strm greater than 1 will initialise zcomp
using multi compression stream zcomp_strm_multi (spinlock-based locking).
default max_comp_streams value is 1, meaning that zram with single stream
will be initialised.
Later patch will introduce configuration knob to change max_comp_streams
on already initialised and used zcomp.
iozone -t 3 -R -r 16K -s 60M -I +Z
test base 1 strm (mutex) 3 strm (spinlock)
-----------------------------------------------------------------------
Initial write 589286.78 583518.39 718011.05
Rewrite 604837.97 596776.38 1515125.72
Random write 584120.11 595714.58 1388850.25
Pwrite 535731.17 541117.38 739295.27
Fwrite 1418083.88 1478612.72 1484927.06
Usage example:
set max_comp_streams to 4
echo 4 > /sys/block/zram0/max_comp_streams
show current max_comp_streams (default value is 1).
cat /sys/block/zram0/max_comp_streams
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
drivers/block/zram/zcomp.c | 126 +++++++++++++++++++++++++++++++++++++++++-
drivers/block/zram/zcomp.h | 2 +-
drivers/block/zram/zram_drv.c | 42 +++++++++++++-
drivers/block/zram/zram_drv.h | 2 +-
4 files changed, 166 insertions(+), 6 deletions(-)
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 210cc28..0b790ac 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -15,6 +15,8 @@
#include "zcomp.h"
+extern struct zcomp_backend zcomp_lzo;
+
/*
* single zcomp_strm backend
*/
@@ -23,7 +25,20 @@ struct zcomp_strm_single {
struct zcomp_strm *zstrm;
};
-extern struct zcomp_backend zcomp_lzo;
+/*
+ * multi zcomp_strm backend
+ */
+struct zcomp_strm_multi {
+ /* protect strm list */
+ spinlock_t strm_lock;
+ /* max possible number of zstrm streams */
+ int max_strm;
+ /* number of available zstrm streams */
+ int avail_strm;
+ /* list of available strms */
+ struct list_head idle_strm;
+ wait_queue_head_t strm_wait;
+};
static struct zcomp_backend *find_backend(const char *compress)
{
@@ -63,6 +78,107 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
return zstrm;
}
+/*
+ * get idle zcomp_strm or wait until other process release
+ * (zcomp_strm_put()) one for us
+ */
+static struct zcomp_strm *zcomp_strm_multi_get(struct zcomp *comp)
+{
+ struct zcomp_strm_multi *zs = comp->stream;
+ struct zcomp_strm *zstrm;
+
+ while (1) {
+ spin_lock(&zs->strm_lock);
+ if (!list_empty(&zs->idle_strm)) {
+ zstrm = list_entry(zs->idle_strm.next,
+ struct zcomp_strm, list);
+ list_del(&zstrm->list);
+ spin_unlock(&zs->strm_lock);
+ return zstrm;
+ }
+ /* zstrm streams limit reached, wait for idle stream */
+ if (zs->avail_strm >= zs->max_strm) {
+ spin_unlock(&zs->strm_lock);
+ wait_event(zs->strm_wait, !list_empty(&zs->idle_strm));
+ continue;
+ }
+ /* allocate new zstrm stream */
+ zs->avail_strm++;
+ spin_unlock(&zs->strm_lock);
+
+ zstrm = zcomp_strm_alloc(comp);
+ if (!zstrm) {
+ spin_lock(&zs->strm_lock);
+ zs->avail_strm--;
+ spin_unlock(&zs->strm_lock);
+ wait_event(zs->strm_wait, !list_empty(&zs->idle_strm));
+ continue;
+ }
+ break;
+ }
+ return zstrm;
+}
+
+/* add stream back to idle list and wake up waiter or free the stream */
+static void zcomp_strm_multi_put(struct zcomp *comp, struct zcomp_strm *zstrm)
+{
+ struct zcomp_strm_multi *zs = comp->stream;
+
+ spin_lock(&zs->strm_lock);
+ if (zs->avail_strm <= zs->max_strm) {
+ list_add(&zstrm->list, &zs->idle_strm);
+ spin_unlock(&zs->strm_lock);
+ wake_up(&zs->strm_wait);
+ return;
+ }
+
+ zs->avail_strm--;
+ spin_unlock(&zs->strm_lock);
+ zcomp_strm_free(comp, zstrm);
+}
+
+static void zcomp_strm_multi_destroy(struct zcomp *comp)
+{
+ struct zcomp_strm_multi *zs = comp->stream;
+ struct zcomp_strm *zstrm;
+
+ while (!list_empty(&zs->idle_strm)) {
+ zstrm = list_entry(zs->idle_strm.next,
+ struct zcomp_strm, list);
+ list_del(&zstrm->list);
+ zcomp_strm_free(comp, zstrm);
+ }
+ kfree(zs);
+}
+
+static int zcomp_strm_multi_create(struct zcomp *comp, int max_strm)
+{
+ struct zcomp_strm *zstrm;
+ struct zcomp_strm_multi *zs;
+
+ comp->destroy = zcomp_strm_multi_destroy;
+ comp->strm_get = zcomp_strm_multi_get;
+ comp->strm_put = zcomp_strm_multi_put;
+ zs = kmalloc(sizeof(struct zcomp_strm_multi), GFP_KERNEL);
+ if (!zs)
+ return -ENOMEM;
+
+ comp->stream = zs;
+ spin_lock_init(&zs->strm_lock);
+ INIT_LIST_HEAD(&zs->idle_strm);
+ init_waitqueue_head(&zs->strm_wait);
+ zs->max_strm = max_strm;
+ zs->avail_strm = 1;
+
+ zstrm = zcomp_strm_alloc(comp);
+ if (!zstrm) {
+ kfree(zs);
+ return -ENOMEM;
+ }
+ list_add(&zstrm->list, &zs->idle_strm);
+ return 0;
+}
+
static struct zcomp_strm *zcomp_strm_single_get(struct zcomp *comp)
{
struct zcomp_strm_single *zs = comp->stream;
@@ -139,7 +255,7 @@ void zcomp_destroy(struct zcomp *comp)
* if requested algorithm is not supported or in case
* of init error
*/
-struct zcomp *zcomp_create(const char *compress)
+struct zcomp *zcomp_create(const char *compress, int max_strm)
{
struct zcomp *comp;
struct zcomp_backend *backend;
@@ -153,7 +269,11 @@ struct zcomp *zcomp_create(const char *compress)
return NULL;
comp->backend = backend;
- if (zcomp_strm_single_create(comp) != 0) {
+ if (max_strm > 1)
+ zcomp_strm_multi_create(comp, max_strm);
+ else
+ zcomp_strm_single_create(comp);
+ if (!comp->stream) {
kfree(comp);
return NULL;
}
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 861e04d..9d77cbf 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -42,7 +42,7 @@ struct zcomp {
void (*destroy)(struct zcomp *comp);
};
-struct zcomp *zcomp_create(const char *comp);
+struct zcomp *zcomp_create(const char *comp, int max_strm);
void zcomp_destroy(struct zcomp *comp);
struct zcomp_strm *zcomp_strm_get(struct zcomp *comp);
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 569ff58..42b9c7f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -108,6 +108,40 @@ static ssize_t mem_used_total_show(struct device *dev,
return sprintf(buf, "%llu\n", val);
}
+static ssize_t max_comp_streams_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ int val;
+ struct zram *zram = dev_to_zram(dev);
+
+ down_read(&zram->init_lock);
+ val = zram->max_comp_streams;
+ up_read(&zram->init_lock);
+
+ return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t max_comp_streams_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ int num;
+ struct zram *zram = dev_to_zram(dev);
+
+ if (kstrtoint(buf, 0, &num))
+ return -EINVAL;
+ if (num < 1)
+ return -EINVAL;
+ down_write(&zram->init_lock);
+ if (init_done(zram)) {
+ up_write(&zram->init_lock);
+ pr_info("Can't set max_comp_streams for initialized device\n");
+ return -EBUSY;
+ }
+ zram->max_comp_streams = num;
+ up_write(&zram->init_lock);
+ return len;
+}
+
/* flag operations needs meta->tb_lock */
static int zram_test_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
@@ -502,6 +536,8 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
}
zcomp_destroy(zram->comp);
+ zram->max_comp_streams = 1;
+
zram_meta_free(zram->meta);
zram->meta = NULL;
/* Reset stats */
@@ -530,7 +566,7 @@ static ssize_t disksize_store(struct device *dev,
return -EBUSY;
}
- zram->comp = zcomp_create(default_compressor);
+ zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
if (!zram->comp) {
up_write(&zram->init_lock);
pr_info("Cannot initialise %s compressing backend\n",
@@ -693,6 +729,8 @@ static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL);
static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
+static DEVICE_ATTR(max_comp_streams, S_IRUGO | S_IWUSR,
+ max_comp_streams_show, max_comp_streams_store);
ZRAM_ATTR_RO(num_reads);
ZRAM_ATTR_RO(num_writes);
@@ -717,6 +755,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_orig_data_size.attr,
&dev_attr_compr_data_size.attr,
&dev_attr_mem_used_total.attr,
+ &dev_attr_max_comp_streams.attr,
NULL,
};
@@ -779,6 +818,7 @@ static int create_device(struct zram *zram, int device_id)
}
zram->meta = NULL;
+ zram->max_comp_streams = 1;
return 0;
out_free_disk:
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 45e04f7..ccf36d1 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -99,7 +99,7 @@ struct zram {
* we can store in a disk.
*/
u64 disksize; /* bytes */
-
+ int max_comp_streams;
struct zram_stats stats;
};
#endif
--
1.9.0.291.g027825b
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