diff --git a/scst/README b/scst/README
index 07fe51637..7e29272ce 100644
--- a/scst/README
+++ b/scst/README
@@ -339,11 +339,11 @@ Module scst supports the following parameters:
default it is approximately TotalMem/4.
-SCST "/proc" commands
+SCST /proc commands
---------------------
For communications with user space programs SCST provides proc-based
-interface in "/proc/scsi_tgt" directory. It contains the following
+interface in /proc/scsi_tgt directory. It contains the following
entries:
- "help" file, which provides online help for SCST commands
@@ -370,14 +370,17 @@ entries:
- "version" file, which shows version of SCST
- "trace_level" file, which allows to read and set trace (logging) level
- for SCST. See "help" file for list of trace levels. If you want to
- enable logging options, which produce a lot of events, like "debug",
- to not loose logged events you should also:
+ for SCST. See /proc/scsi_tgt/help file for list of commands and
+ trace levels. If you want to enable logging options, which produce a
+ lot of events, like "debug", to not loose logged events you should
+ also:
* Increase in .config of your kernel CONFIG_LOG_BUF_SHIFT variable
- to much bigger value, then recompile it. For example, I use 25,
- but to use it I needed to modify the maximum allowed value for
- CONFIG_LOG_BUF_SHIFT in the corresponding Kconfig.
+ to much bigger value, then recompile it. For example, value 25
+ will provide good protection from logging overflow aven under
+ high volume of loggin events, but to use it you will need to
+ modify the maximum allowed value for CONFIG_LOG_BUF_SHIFT in the
+ corresponding Kconfig file.
* Change in your /etc/syslog.conf or other config file of your favorite
logging program to store kernel logs in async manner. For example,
@@ -573,10 +576,10 @@ LUNs in them.
VDISK device handler
--------------------
-After loading VDISK device handler creates in "/proc/scsi_tgt/"
+After loading VDISK device handler creates in /proc/scsi_tgt/
subdirectories "vdisk" and "vcdrom". They have similar layout:
- - "trace_level" and "type" files as described for other dev handlers
+ - "trace_level" and "type" files as described above
- "help" file, which provides online help for VDISK commands
@@ -647,6 +650,22 @@ mode is used.
For example, "echo "open disk1 /vdisks/disk1" >/proc/scsi_tgt/vdisk/vdisk"
will open file /vdisks/disk1 as virtual FILEIO disk with name "disk1".
+Also the VDISK handler has module parameter "num_threads", which
+specifies count of I/O threads for each VDISK's device. If you have a
+workload, which tends to produce rather random accesses (e.g. DB-like),
+you should increase this count to a bigger value, like 32. If you have a
+rather sequential workload, you should decrease it to a lower value,
+like number of CPUs on the target or even 1. Due to some limitations of
+Linux I/O subsystem, increasing number of I/O threads leads to
+performance drop, especially with deadline scheduler, so decreasing it
+can improve sequential performance. The default provides a good
+compromise between random and sequential accesses.
+
+You shouldn't be afraid to have too many VDISK I/O threads if you have
+many VDISK devices. Kernel threads consume very little amount of
+resources (several KBs) and only necessary threads will be used by SCST,
+so the threads will not trash your system.
+
CAUTION: If you partitioned/formatted your device with block size X, *NEVER*
======== ever try to export and then mount it (even accidentally) with another
block size. Otherwise you can *instantly* damage it pretty
diff --git a/scst/README_in-tree b/scst/README_in-tree
index 15f08e821..7029d25cc 100644
--- a/scst/README_in-tree
+++ b/scst/README_in-tree
@@ -257,11 +257,11 @@ Module scst supports the following parameters:
consumed by the SCST commands for data buffers at any given time. By
default it is approximately TotalMem/4.
-SCST "/proc" commands
+SCST /proc commands
---------------------
For communications with user space programs SCST provides proc-based
-interface in "/proc/scsi_tgt" directory. It contains the following
+interface in /proc/scsi_tgt directory. It contains the following
entries:
- "help" file, which provides online help for SCST commands
@@ -288,14 +288,17 @@ entries:
- "version" file, which shows version of SCST
- "trace_level" file, which allows to read and set trace (logging) level
- for SCST. See "help" file for list of trace levels. If you want to
- enable logging options, which produce a lot of events, like "debug",
- to not loose logged events you should also:
+ for SCST. See /proc/scsi_tgt/help file for list of commands and
+ trace levels. If you want to enable logging options, which produce a
+ lot of events, like "debug", to not loose logged events you should
+ also:
* Increase in .config of your kernel CONFIG_LOG_BUF_SHIFT variable
- to much bigger value, then recompile it. For example, I use 25,
- but to use it I needed to modify the maximum allowed value for
- CONFIG_LOG_BUF_SHIFT in the corresponding Kconfig.
+ to much bigger value, then recompile it. For example, value 25
+ will provide good protection from logging overflow aven under
+ high volume of loggin events, but to use it you will need to
+ modify the maximum allowed value for CONFIG_LOG_BUF_SHIFT in the
+ corresponding Kconfig file.
* Change in your /etc/syslog.conf or other config file of your favorite
logging program to store kernel logs in async manner. For example,
@@ -489,10 +492,10 @@ LUNs in them.
VDISK device handler
--------------------
-After loading VDISK device handler creates in "/proc/scsi_tgt/"
+After loading VDISK device handler creates in /proc/scsi_tgt/
subdirectories "vdisk" and "vcdrom". They have similar layout:
- - "trace_level" and "type" files as described for other dev handlers
+ - "trace_level" and "type" files as described above
- "help" file, which provides online help for VDISK commands
@@ -563,6 +566,22 @@ mode is used.
For example, "echo "open disk1 /vdisks/disk1" >/proc/scsi_tgt/vdisk/vdisk"
will open file /vdisks/disk1 as virtual FILEIO disk with name "disk1".
+Also the VDISK handler has module parameter "num_threads", which
+specifies count of I/O threads for each VDISK's device. If you have a
+workload, which tends to produce rather random accesses (e.g. DB-like),
+you should increase this count to a bigger value, like 32. If you have a
+rather sequential workload, you should decrease it to a lower value,
+like number of CPUs on the target or even 1. Due to some limitations of
+Linux I/O subsystem, increasing number of I/O threads leads to
+performance drop, especially with deadline scheduler, so decreasing it
+can improve sequential performance. The default provides a good
+compromise between random and sequential accesses.
+
+You shouldn't be afraid to have too many VDISK I/O threads if you have
+many VDISK devices. Kernel threads consume very little amount of
+resources (several KBs) and only necessary threads will be used by SCST,
+so the threads will not trash your system.
+
CAUTION: If you partitioned/formatted your device with block size X, *NEVER*
======== ever try to export and then mount it (even accidentally) with another
block size. Otherwise you can *instantly* damage it pretty
diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index 10eb2688c..9ed2efdf6 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -232,7 +232,12 @@ struct scst_vdisk_thr {
static struct kmem_cache *vdisk_thr_cachep;
static struct kmem_cache *blockio_work_cachep;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 29)
#define DEF_NUM_THREADS 5
+#else
+/* Context RA patch supposed to be applied on the kernel */
+#define DEF_NUM_THREADS 8
+#endif
static int num_threads = DEF_NUM_THREADS;
module_param_named(num_threads, num_threads, int, S_IRUGO);
diff --git a/scst/src/scst_mem.c b/scst/src/scst_mem.c
index 94fe41970..dcbeaa9c0 100644
--- a/scst/src/scst_mem.c
+++ b/scst/src/scst_mem.c
@@ -1293,7 +1293,6 @@ int sgv_pool_init(struct sgv_pool *pool, const char *name,
{
int res = -ENOMEM;
int i;
- struct sgv_pool_obj *obj;
TRACE_ENTRY();
@@ -1335,8 +1334,8 @@ int sgv_pool_init(struct sgv_pool *pool, const char *name,
TRACE_MEM("name %s, sizeof(*obj)=%zd, clustering_type=%d, "
"single_alloc_pages=%d, max_caches=%d, max_cached_pages=%d",
- name, sizeof(*obj), clustering_type, single_alloc_pages,
- pool->max_caches, pool->max_cached_pages);
+ name, sizeof(struct sgv_pool_obj), clustering_type,
+ single_alloc_pages, pool->max_caches, pool->max_cached_pages);
strncpy(pool->name, name, sizeof(pool->name)-1);
pool->name[sizeof(pool->name)-1] = '\0';
diff --git a/www/comparison.html b/www/comparison.html
index a0a3328f7..188a84f67 100644
--- a/www/comparison.html
+++ b/www/comparison.html
@@ -167,7 +167,7 @@ ORDERED commands | + | + | -,
data
| Persistent Reservations
(Windows 2008 clustering / RHEL5 I/O fencing) | Under development,
patch is
+ "http://sourceforge.net/mailarchive/message.php?msg_name=4A9C21DE.6050700%40open-e.com">
available for
testing | - | - | Under development |