Hi Xose and Christophe,
On 2017/5/11 6:36, Xose Vazquez Perez wrote:
> On 05/08/2017 05:58 AM, Yang Feng wrote:
>
>> Prioritizer for device mapper multipath, where the corresponding priority
>> values of specific paths are provided by a time-delay algorithm. And the
>> time-delay algorithm is dependent on the following arguments(delay_interval,
>> cons_num).
> This new feature should be documented in multipath/multipath.conf.5
>
multipath/multipath.conf.5 has be documented in the following patch.
>> diff --git a/libmultipath/checkers/Makefile b/libmultipath/checkers/Makefile
>> index 4970fc0..7e433ca 100644
>> --- a/libmultipath/checkers/Makefile
>> +++ b/libmultipath/checkers/Makefile
>> @@ -14,19 +14,16 @@ LIBS= \
>> libcheckemc_clariion.so \
>> libcheckhp_sw.so \
>> libcheckrdac.so
>> -ifneq ($(ENABLE_RADOS),0)
>> -LIBS += libcheckrbd.so
>> -endif
>
> Is it right?
>
>
Thanks, fixed as the flollowing patch.
---
Prioritizer for device mapper multipath, where the corresponding priority values of specific paths are provided by a time-delay algorithm. And the time-delay algorithm is dependent on the following arguments(delay_interval, cons_num).
The principle of the algorithm is illustrated as follows:
1. By sending a certain number "cons_num" of read IOs to the current path
continuously, the IOs' average delay can be calculated.
2. According to the average delay of each path and the weight value
"delay_interval", the priority "rc" of each path can be provided.
delay_interval delay_interval delay_interval delay_interval
|---------------|---------------|---------------| |---------------|
|priority rank 1|priority rank 2|priority rank 3|... |priority rank x|
|---------------|---------------|---------------| |---------------|
Priority Rank Partitioning
---
libmultipath/Makefile | 2 +-
libmultipath/checkers/Makefile | 4 +-
libmultipath/checkers/emc_clariion.c | 2 +-
libmultipath/checkers/libsg.c | 94 ------------
libmultipath/checkers/libsg.h | 9 --
libmultipath/checkers/readsector0.c | 2 +-
libmultipath/libsg.c | 94 ++++++++++++
libmultipath/libsg.h | 9 ++
libmultipath/prioritizers/Makefile | 6 +-
libmultipath/prioritizers/delayedpath.c | 246 ++++++++++++++++++++++++++++++++
libmultipath/prioritizers/delayedpath.h | 14 ++
multipath/multipath.conf.5 | 19 +++++++++++++++++++
12 files changed, 392 insertions(+), 109 deletions(-) delete mode 100644 libmultipath/checkers/libsg.c delete mode 100644 libmultipath/checkers/libsg.h create mode 100644 libmultipath/libsg.c create mode 100644 libmultipath/libsg.h create mode 100644 libmultipath/prioritizers/delayedpath.c
create mode 100644 libmultipath/prioritizers/delayedpath.h
diff --git a/libmultipath/Makefile b/libmultipath/Makefile index 1f5ec25..a4d725a 100644
--- a/libmultipath/Makefile
+++ b/libmultipath/Makefile
@@ -41,7 +41,7 @@ OBJS = memory.o parser.o vector.o devmapper.o callout.o \
structs.o discovery.o propsel.o dict.o \
pgpolicies.o debug.o defaults.o uevent.o time-util.o \
switchgroup.o uxsock.o print.o alias.o log_pthread.o \
- log.o configure.o structs_vec.o sysfs.o prio.o checkers.o \
+ log.o configure.o structs_vec.o sysfs.o libsg.o prio.o checkers.o \
lock.o waiter.o file.o wwids.o prioritizers/alua_rtpg.o
all: $(LIBS)
diff --git a/libmultipath/checkers/Makefile b/libmultipath/checkers/Makefile index 4970fc0..7e433ca 100644
--- a/libmultipath/checkers/Makefile
+++ b/libmultipath/checkers/Makefile
@@ -14,19 +14,16 @@ LIBS= \
libcheckemc_clariion.so \
libcheckhp_sw.so \
libcheckrdac.so
ifneq ($(ENABLE_RADOS),0)
LIBS += libcheckrbd.so
endif
all: $(LIBS)
libcheckrbd.so: rbd.o
$(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^ -lrados -ludev
-libcheckdirectio.so: libsg.o directio.o
+libcheckdirectio.so: ../libsg.o directio.o
$(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^ -laio
-libcheck%.so: libsg.o %.o
+libcheck%.so: ../libsg.o %.o
$(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^
install:
diff --git a/libmultipath/checkers/emc_clariion.c b/libmultipath/checkers/emc_clariion.c
index 9c1ffed..e4ba757 100644
--- a/libmultipath/checkers/emc_clariion.c
+++ b/libmultipath/checkers/emc_clariion.c
@@ -12,7 +12,7 @@
#include <errno.h>
#include "../libmultipath/sg_include.h"
-#include "libsg.h"
+#include "../libmultipath/libsg.h"
#include "checkers.h"
#include "debug.h"
#include "memory.h"
diff --git a/libmultipath/checkers/libsg.c b/libmultipath/checkers/libsg.c deleted file mode 100644 index 958ea92..0000000
--- a/libmultipath/checkers/libsg.c
+++ /dev/null
@@ -1,94 +0,0 @@
-/*
- * Copyright (c) 2004, 2005 Christophe Varoqui
- */
-#include <string.h>
-#include <sys/ioctl.h>
-#include <errno.h>
-#include <sys/stat.h>
-
-#include "checkers.h"
-#include "libsg.h"
-#include "../libmultipath/sg_include.h"
-
-int
-sg_read (int sg_fd, unsigned char * buff, int buff_len,
- unsigned char * sense, int sense_len, unsigned int timeout)
-{
- /* defaults */
- int blocks;
- long long start_block = 0;
- int bs = 512;
- int cdbsz = 10;
-
- unsigned char rdCmd[cdbsz];
- unsigned char *sbb = sense;
- struct sg_io_hdr io_hdr;
- int res;
- int rd_opcode[] = {0x8, 0x28, 0xa8, 0x88};
- int sz_ind;
- struct stat filestatus;
- int retry_count = 3;
-
- if (fstat(sg_fd, &filestatus) != 0)
- return PATH_DOWN;
- bs = (filestatus.st_blksize > 4096)? 4096: filestatus.st_blksize;
- blocks = buff_len / bs;
- memset(rdCmd, 0, cdbsz);
- sz_ind = 1;
- rdCmd[0] = rd_opcode[sz_ind];
- rdCmd[2] = (unsigned char)((start_block >> 24) & 0xff);
- rdCmd[3] = (unsigned char)((start_block >> 16) & 0xff);
- rdCmd[4] = (unsigned char)((start_block >> 8) & 0xff);
- rdCmd[5] = (unsigned char)(start_block & 0xff);
- rdCmd[7] = (unsigned char)((blocks >> 8) & 0xff);
- rdCmd[8] = (unsigned char)(blocks & 0xff);
-
- memset(&io_hdr, 0, sizeof(struct sg_io_hdr));
- io_hdr.interface_id = 'S';
- io_hdr.cmd_len = cdbsz;
- io_hdr.cmdp = rdCmd;
- io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
- io_hdr.dxfer_len = bs * blocks;
- io_hdr.dxferp = buff;
- io_hdr.mx_sb_len = sense_len;
- io_hdr.sbp = sense;
- io_hdr.timeout = timeout * 1000;
- io_hdr.pack_id = (int)start_block;
-
-retry:
- memset(sense, 0, sense_len);
- while (((res = ioctl(sg_fd, SG_IO, &io_hdr)) < 0) && (EINTR == errno));
-
- if (res < 0) {
- if (ENOMEM == errno) {
- return PATH_UP;
- }
- return PATH_DOWN;
- }
-
- if ((0 == io_hdr.status) &&
- (0 == io_hdr.host_status) &&
- (0 == io_hdr.driver_status)) {
- return PATH_UP;
- } else {
- int key = 0;
-
- if (io_hdr.sb_len_wr > 3) {
- if (sbb[0] == 0x72 || sbb[0] == 0x73)
- key = sbb[1] & 0x0f;
- else if (io_hdr.sb_len_wr > 13 &&
- ((sbb[0] & 0x7f) == 0x70 ||
- (sbb[0] & 0x7f) == 0x71))
- key = sbb[2] & 0x0f;
- }
-
- /*
- * Retry if UNIT_ATTENTION check condition.
- */
- if (key == 0x6) {
- if (--retry_count)
- goto retry;
- }
- return PATH_DOWN;
- }
-}
diff --git a/libmultipath/checkers/libsg.h b/libmultipath/checkers/libsg.h deleted file mode 100644 index 3994f45..0000000
--- a/libmultipath/checkers/libsg.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#ifndef _LIBSG_H
-#define _LIBSG_H
-
-#define SENSE_BUFF_LEN 32
-
-int sg_read (int sg_fd, unsigned char * buff, int buff_len,
- unsigned char * sense, int sense_len, unsigned int timeout);
-
-#endif /* _LIBSG_H */
diff --git a/libmultipath/checkers/readsector0.c b/libmultipath/checkers/readsector0.c
index 8fccb46..d70c5c5 100644
--- a/libmultipath/checkers/readsector0.c
+++ b/libmultipath/checkers/readsector0.c
@@ -4,7 +4,7 @@
#include <stdio.h>
#include "checkers.h"
-#include "libsg.h"
+#include "../libmultipath/libsg.h"
#define MSG_READSECTOR0_UP "readsector0 checker reports path is up"
#define MSG_READSECTOR0_DOWN "readsector0 checker reports path is down"
diff --git a/libmultipath/libsg.c b/libmultipath/libsg.c new file mode 100644 index 0000000..99c91a4
--- /dev/null
+++ b/libmultipath/libsg.c
@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2004, 2005 Christophe Varoqui */ #include <string.h>
+#include <sys/ioctl.h> #include <errno.h> #include <sys/stat.h>
+
+#include "checkers.h"
+#include "libsg.h"
+#include "sg_include.h"
+
+int
+sg_read (int sg_fd, unsigned char * buff, int buff_len,
+ unsigned char * sense, int sense_len, unsigned int timeout) {
+ /* defaults */
+ int blocks;
+ long long start_block = 0;
+ int bs = 512;
+ int cdbsz = 10;
+
+ unsigned char rdCmd[cdbsz];
+ unsigned char *sbb = sense;
+ struct sg_io_hdr io_hdr;
+ int res;
+ int rd_opcode[] = {0x8, 0x28, 0xa8, 0x88};
+ int sz_ind;
+ struct stat filestatus;
+ int retry_count = 3;
+
+ if (fstat(sg_fd, &filestatus) != 0)
+ return PATH_DOWN;
+ bs = (filestatus.st_blksize > 4096)? 4096: filestatus.st_blksize;
+ blocks = buff_len / bs;
+ memset(rdCmd, 0, cdbsz);
+ sz_ind = 1;
+ rdCmd[0] = rd_opcode[sz_ind];
+ rdCmd[2] = (unsigned char)((start_block >> 24) & 0xff);
+ rdCmd[3] = (unsigned char)((start_block >> 16) & 0xff);
+ rdCmd[4] = (unsigned char)((start_block >> 8) & 0xff);
+ rdCmd[5] = (unsigned char)(start_block & 0xff);
+ rdCmd[7] = (unsigned char)((blocks >> 8) & 0xff);
+ rdCmd[8] = (unsigned char)(blocks & 0xff);
+
+ memset(&io_hdr, 0, sizeof(struct sg_io_hdr));
+ io_hdr.interface_id = 'S';
+ io_hdr.cmd_len = cdbsz;
+ io_hdr.cmdp = rdCmd;
+ io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
+ io_hdr.dxfer_len = bs * blocks;
+ io_hdr.dxferp = buff;
+ io_hdr.mx_sb_len = sense_len;
+ io_hdr.sbp = sense;
+ io_hdr.timeout = timeout * 1000;
+ io_hdr.pack_id = (int)start_block;
+
+retry:
+ memset(sense, 0, sense_len);
+ while (((res = ioctl(sg_fd, SG_IO, &io_hdr)) < 0) && (EINTR ==
+errno));
+
+ if (res < 0) {
+ if (ENOMEM == errno) {
+ return PATH_UP;
+ }
+ return PATH_DOWN;
+ }
+
+ if ((0 == io_hdr.status) &&
+ (0 == io_hdr.host_status) &&
+ (0 == io_hdr.driver_status)) {
+ return PATH_UP;
+ } else {
+ int key = 0;
+
+ if (io_hdr.sb_len_wr > 3) {
+ if (sbb[0] == 0x72 || sbb[0] == 0x73)
+ key = sbb[1] & 0x0f;
+ else if (io_hdr.sb_len_wr > 13 &&
+ ((sbb[0] & 0x7f) == 0x70 ||
+ (sbb[0] & 0x7f) == 0x71))
+ key = sbb[2] & 0x0f;
+ }
+
+ /*
+ * Retry if UNIT_ATTENTION check condition.
+ */
+ if (key == 0x6) {
+ if (--retry_count)
+ goto retry;
+ }
+ return PATH_DOWN;
+ }
+}
diff --git a/libmultipath/libsg.h b/libmultipath/libsg.h new file mode 100644 index 0000000..3994f45
--- /dev/null
+++ b/libmultipath/libsg.h
@@ -0,0 +1,9 @@
+#ifndef _LIBSG_H
+#define _LIBSG_H
+
+#define SENSE_BUFF_LEN 32
+
+int sg_read (int sg_fd, unsigned char * buff, int buff_len,
+ unsigned char * sense, int sense_len, unsigned int timeout);
+
+#endif /* _LIBSG_H */
diff --git a/libmultipath/prioritizers/Makefile b/libmultipath/prioritizers/Makefile
index 36b42e4..7e3da51 100644
--- a/libmultipath/prioritizers/Makefile
+++ b/libmultipath/prioritizers/Makefile
@@ -18,13 +18,17 @@ LIBS = \
libpriorandom.so \
libpriordac.so \
libprioweightedpath.so \
- libpriosysfs.so
+ libpriodelayedpath.so \
+ libpriosysfs.so
all: $(LIBS)
libprioalua.so: alua.o alua_rtpg.o
$(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^
+libpriodelayedpath.so: delayedpath.o ../libsg.o
+ $(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^
+
libprio%.so: %.o
$(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^
diff --git a/libmultipath/prioritizers/delayedpath.c b/libmultipath/prioritizers/delayedpath.c
new file mode 100644
index 0000000..4c1cfea
--- /dev/null
+++ b/libmultipath/prioritizers/delayedpath.c
@@ -0,0 +1,246 @@
+/*
+ * (C) Copyright HUAWEI Technology Corp. 2017, 2021 All Rights Reserved.
+ *
+ * main.c
+ *
+ * Prioritizer for device mapper multipath, where the corresponding
+priority
+ * values of specific paths are provided by a time-delay algorithm. And
+the
+ * time-delay algorithm is dependent on arguments.
+ *
+ * The principle of the algorithm as follows:
+ * 1. By sending a certain number "cons_num" of read IOs to the current path
+ * continuously, the IOs' average delay can be calculated.
+ * 2. According to the average delay of each path and the weight value
+ * "delay_interval", the priority "rc" of each path can be provided.
+ *
+ * Author(s): Yang Feng <philip.yang@xxxxxxxxxx>
+ * Zou Ming <zouming.zouming@xxxxxxxxxx>
+ *
+ * This file is released under the GPL.
+ */
+#include <stdio.h>
+#include <ctype.h>
+#include <sys/time.h>
+
+#include "debug.h"
+#include "prio.h"
+#include "structs.h"
+#include "../libmultipath/libsg.h"
+
+#include "delayedpath.h"
+
+#define THRES_USEC_VALUE 300000000LL /*USEC, 300SEC*/
+#define DEFAULT_DELAY_INTERVAL 10 /*MSEC*/
+#define DEFAULT_CONS_NUM 20
+
+#define MAX_CHAR_SIZE 30
+
+#define CHAR_SEC "SEC"
+#define CHAR_MSEC "MSEC"
+#define CHAR_USEC "USEC"
+
+enum interval_type {
+ INTERVAL_SEC,
+ INTERVAL_MSEC,
+ INTERVAL_USEC,
+ INTERVAL_INVALID
+};
+
+static int conversion_ratio[] = {
+ [INTERVAL_SEC] = USEC_PER_SEC,
+ [INTERVAL_MSEC] = USEC_PER_MSEC,
+ [INTERVAL_USEC] = USEC_PER_USEC,
+ [INTERVAL_INVALID] = 0,
+};
+
+
+static int do_readsector0(int fd, unsigned int timeout) {
+ unsigned char buf[4096];
+ unsigned char sbuf[SENSE_BUFF_LEN];
+ int ret;
+
+ ret = sg_read(fd, &buf[0], 4096, &sbuf[0],
+ SENSE_BUFF_LEN, timeout);
+
+ return ret;
+}
+
+static int get_interval_type(char *source, char *type) {
+ /*is USEC*/
+ if ((strstr(source, CHAR_USEC) != NULL)
+ && (strstr(source, CHAR_USEC)[4] == '|'))
+ {
+ memcpy(type, CHAR_USEC, strlen(CHAR_USEC)+1);
+ return INTERVAL_USEC;
+ }
+
+ /*is MSEC*/
+ if ((strstr(source, CHAR_MSEC) != NULL)
+ && (strstr(source, CHAR_MSEC)[4] == '|'))
+ {
+ memcpy(type, CHAR_MSEC, strlen(CHAR_MSEC)+1);
+ return INTERVAL_MSEC;
+ }
+
+ /*is SEC*/
+ if ((strstr(source, CHAR_SEC) != NULL)
+ && (strstr(source, CHAR_SEC)[4] == '|'))
+ {
+ memcpy(type, CHAR_SEC, strlen(CHAR_SEC)+1);
+ return INTERVAL_SEC;
+ }
+
+ return INTERVAL_INVALID;
+}
+
+static int get_string_from_vertica(char *args,
+ char *beforestring,
+ char *afterstring,
+ int *type) {
+ char source[MAX_CHAR_SIZE];
+ char char_type[MAX_CHAR_SIZE];
+ char vertica[] = "|";
+ char *token = NULL;
+ char *tmp = NULL;
+ char *saveptr = NULL;
+ unsigned int size = strlen(args);
+
+ if ((args == NULL) || (beforestring == NULL)
+ || (afterstring == NULL) || (type == NULL))
+ return 0;
+
+ /* int type */
+ if ((size < 1) || (size > MAX_CHAR_SIZE-1))
+ return 0;
+
+ memcpy(source, args, size+1);
+ if (strstr(source, vertica) == NULL)
+ return 0;
+
+ *type = get_interval_type(source, char_type);
+ if (*type == INTERVAL_INVALID)
+ return 0;
+
+ token = strtok_r(source, vertica, &saveptr);
+ token = strtok(token, char_type);
+ if ((token == NULL) || (saveptr == NULL))
+ return 0;
+
+ tmp = token;
+ while (*tmp != '\0')
+ if (!isdigit(*tmp++))
+ return 0;
+
+ tmp = saveptr;
+ while (*tmp != '\0')
+ if (!isdigit(*tmp++))
+ return 0;
+
+ strncpy(beforestring, token, strlen(token) + 1);
+ strncpy(afterstring, saveptr, strlen(saveptr) + 1);
+ return 1;
+}
+
+int checkargvalid(int delay_interval, int cons_num, int type) {
+ if (type == INTERVAL_SEC)
+ {
+ if ((delay_interval < 1) || (delay_interval > 60))
+ return 0;
+ }
+ else if (type != INTERVAL_INVALID)
+ {
+ if ((delay_interval < 1) || (delay_interval >= 1000))
+ return 0;
+ }
+
+ if ((cons_num < 3) || (cons_num > 1000))
+ return 0;
+
+ return 1;
+}
+
+int get_delay_pref_arg(char *args, int *delay_interval, int *cons_num,
+int *type) {
+ char delayintervalstr[MAX_CHAR_SIZE];
+ char consnumstr[MAX_CHAR_SIZE];
+
+ if (get_string_from_vertica(args, delayintervalstr, consnumstr, type) == 0)
+ return 0;
+
+ *delay_interval = atoi(delayintervalstr);
+ *cons_num = atoi(consnumstr);
+
+ if (checkargvalid(*delay_interval, *cons_num, *type) == 0)
+ return 0;
+
+ return 1;
+}
+
+long long get_conversion_ratio(int type) {
+ return conversion_ratio[type];
+}
+
+int getprio (struct path *pp, char *args, unsigned int timeout) {
+ int rc, delay_interval, cons_num, type, temp;
+ long long delay, avgdelay, ratio;
+ long long min = THRES_USEC_VALUE;
+ long long max = 0;
+ long long toldelay = 0;
+ long long before, after;
+ struct timeval tv;
+
+ if (get_delay_pref_arg(args, &delay_interval, &cons_num, &type) == 0)
+ {
+ condlog(3, "%s: get delay arg fail", pp->dev);
+ delay_interval = DEFAULT_DELAY_INTERVAL;
+ cons_num = DEFAULT_CONS_NUM;
+ type = INTERVAL_MSEC;
+ }
+
+ temp = cons_num;
+ while (temp-- > 0)
+ {
+ (void)gettimeofday(&tv, NULL);
+ before = timeval_to_us(&tv);
+
+ if (do_readsector0(pp->fd, timeout) == 2)
+ {
+ condlog(0, "%s: path down", pp->dev);
+ return 1;
+ }
+
+ (void)gettimeofday(&tv, NULL);
+ after = timeval_to_us(&tv);
+
+ delay = after - before;
+ if (delay < 0)
+ {
+ condlog(0, "%s: delay calc error", pp->dev);
+ return 1;
+ }
+
+ min = (min <= delay) ? min : delay;
+ max = (max >= delay) ? max : delay;
+
+ toldelay += delay;
+ }
+
+ toldelay -= min + max;
+ avgdelay = toldelay/(long long)(cons_num - 2);
+ if (avgdelay > THRES_USEC_VALUE)
+ {
+ condlog(0, "%s: avgdelay is more than thresold", pp->dev);
+ return 1;
+ }
+
+ ratio = get_conversion_ratio(type);
+ rc = (int)(THRES_USEC_VALUE - (avgdelay/(((long long)delay_interval) *
+ratio)));
+
+ return rc;
+}
diff --git a/libmultipath/prioritizers/delayedpath.h b/libmultipath/prioritizers/delayedpath.h
new file mode 100644
index 0000000..ca89702
--- /dev/null
+++ b/libmultipath/prioritizers/delayedpath.h
@@ -0,0 +1,14 @@
+#ifndef _DELAYEDPATH_H
+#define _DELAYEDPATH_H
+
+#define PRIO_DELAYED_PATH "delayedpath"
+#define USEC_PER_SEC 1000000LL
+#define USEC_PER_MSEC 1000LL
+#define USEC_PER_USEC 1LL
+
+static inline long long timeval_to_us(const struct timeval *tv) {
+ return ((long long) tv->tv_sec * USEC_PER_SEC) + tv->tv_usec; }
+
+#endif
diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
index 5939688..b787634 100644
--- a/multipath/multipath.conf.5
+++ b/multipath/multipath.conf.5
@@ -293,6 +293,10 @@ Generate a random priority between 1 and 10.
Generate the path priority based on the regular expression and the
priority provided as argument. Requires prio_args keyword.
.TP
+.I delayedpath
+Generate the path priority based on a time-delay algorithm.
+Requires prio_args keyword.
+.TP
.I datacore
.\" XXX
???. Requires prio_args keyword.
@@ -333,6 +337,21 @@ these values can be looked up through sysfs or by running \fImultipathd show pat
"%N:%R:%n:%r"\fR. For example: 0x200100e08ba0aea0:0x210100e08ba0aea0:.*:.* , .*:.*:iqn.2009-10.com.redhat.msp.lab.ask-06:.*
.RE
.TP 12
+.I delayed
+Needs a value of the form
+\fI"<delay_interval|cons_num>"\fR
+.RS
+.TP 8
+.I delay_interval
+The interval values of average IO-time-delay between two different neighbour ranks of path priority, used to partition different priority ranks.
+Form: XXSEC, or XXXUSEC, or XXXMSEC. Unit: Second, or Microsecond, or Millisecond. Valid Values: Integer, SEC [1, 60], USEC [1, 1000), MSEC [1, 1000),
+For example: 10SEC, or 100USEC, or 100MSEC. The default is: 10MSEC.
+.TP
+.I cons_num
+The number of read IOs sent to the current path continuously, used to calculate the average IO-time-delay. Valid Values: Integer, [3, 1000].
+For example: 30. The default is: 20.
+.RE
+.TP 12
.I alua
If \fIexclusive_pref_bit\fR is set, paths with the \fIpreferred path\fR bit
set will always be in their own path group.
--
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