[dm-devel] [PATCH] multipath-tools:Prioritizer based on a time-delay algorithm
Yang Feng
philip.yang at huawei.com
Tue May 16 14:53:17 UTC 2017
Hello Martin,
How about this patch?
Thanks a lot,
Best regards.
On 2017/5/15 18:44, Yang Feng wrote:
> Hello Martin,
>
> Thank you very much for your remarks. I am sorry for late reply, Please find my answer and the updated patch.
>
>> Hello Yang,
>>
>> thank you for your work. Please find my remarks below.
>>
>> On Mon, 2017-05-08 at 11:58 +0800, 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).
>>> 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_inter
>>
>> How does this algorithm behave under load? Can we be sure that
>> priorities don't start to fluctuate wildly because busy paths will
>> usually have longer latencies than idle ones?
> I have a lot of test under load. When the appropriate value of argument "delay_interval" is set,
> this algorithm behave well and can separate the paths who's average delay is more than others.
> When add a new path or the path's state change from down to up, getprio() of the prioritizer is triggered, and
> the current path is not under IOs.
>
>>> libmultipath/Makefile | 2 +-
>>> libmultipath/checkers/Makefile | 7 +-
>>> 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
>>
>> Why do you have to move libsg for this? It's already used by various
>> checkers, why can't your checker do the same? If you really need to do
>> it, you should at least separate that part of the patch from the added
>> code.
> OK, this time, libsg will not be moved.
>
>>> +
>>> +#define CHAR_SEC "SEC"
>>> +#define CHAR_MSEC "MSEC"
>>> +#define CHAR_USEC "USEC"
>>
>> I suggest to use "s", "ms", and "us" here instead.
> OK, as the following patch.
>
>> If you create an array of "const char*" instead like you did for
>> conversion_ratio below, you could implement get_interval_type() more
>> elegantly using a loop over that array.
> OK, as the following patch.
>
>>> +static int get_interval_type(char *source, char *type)
>>> +{
>>> + /*is USEC*/
>>> + if ((strstr(source, CHAR_USEC) != NULL)
>>> + && (strstr(source, CHAR_USEC)[4] == '_'))
>>
>> Please avoid these double strstr() invocation. The compiler may
>> optimize it away, but it just looks strange. The following would
>> look better to me, and I find it actually more readable:
>>
>> if (((p = strstr(source, CHAR_USEC)) != NULL) && p[4] == '_')
> OK, as the following patch.
>
>>> +static int get_string_from_under(char *args,
>>> + char *beforestring,
>>> + char *afterstring,
>>> + int *type)
>>
>> Maybe you could figure out a more descriptive name for this function?
>>
>> A comment in the code showing how the string to be parsed typically
>> looks like would be helpful for the reader.
> OK, as the following patch.
>
>>> + token = strtok_r(source, under, &saveptr);
>>> + token = strtok(token, char_type);
>>
>> I'm pretty sure this is is not what you intended to write. If char_type
>> is "usec", this would split the string at the possible delimiters 'u',
>> 's', 'e', and 'c' (the 2nd argument of strtok(3) is not a sequence, but
>> a 'set' of bytes). It might accidentally work with the input strings
>> you are using (in particular because you only look at the first token),
>> but nevertheless it's wrong.
> OK, as the following patch.
>
>>> + 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;
>>> +}
>>
>> I don't think it's safe to use saveptr the way you do it. The strtok_r
>> man page says this parameter is for "internal use". While it makes
>> sense to assume that it points to the next token, I'm not sure if
>> that's guaranteed. You would be safe by calling
>>
>> somevar = strtok_r(NULL, under, &saveptr)
>>
>> and use "somevar".
> OK, as the following patch.
>
>>
>> In general, this whole parsing code is odd. IIUC this parses input
>> looking like ([0-9]+)(SEC|MSEC|USEC)_([0-9]+) and sets beforestring,
>> type, and afterstring to the regex matches \1, \2, and \3,
>> respectively.
>>
>> Why don't you start parsing from the beginning of the input, e.g. with
>> strtoul(), and look at the rest later?
> OK, as the following patch.
>
>>> +
>>> +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;
>>> + }
>>
>> You could be more forgiving here. 15000MSEC could be a legal value.
> Because this value is more than 1 second, you can use the unit second.
>
>>
>>> +
>>> + 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_under(args, delayintervalstr, consnumstr,
>>> type) == 0)
>>> + return 0;
>>
>> It might be good to write the parser so that the consnum part can be
>> left out by the user, and assume a reasonable default in that case.
> OK, as the following patch.
>
>>> + 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);
>>
>> It's better to use clock_gettime(CLOCK_MONOTONIC, ...) here. Then you
>> can throw away the delay < 0 check below.
> OK, as the following patch.
>
>>> + 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;
>>> +}
>>
>> Is it reasonable to do these interval calculations synchronously in
>> getprio()? cons_num is limited to 1000, so this routine could issue
>> 1000 reads on the device before returning. In particular if the device
>> is under IO load and the delay is high, execution if this routine could
>> be really slow.
>>
>> It would make more sense to me to have a separate thread that
>> calculates some sort of "running average" for the delay of the
>> different paths, and have getprio() just fetch the current value of
>> that variable.
>>
>> Regards
>> Martin
>>
> When add a new path or the path's state change from down to up, getprio() of the prioritizer is triggered, and
> the current path is not under IOs.
> Usually, the 1000 reads will be finish fastly.
> And have getprio() need to get the up-to-date average delay of the current path, these interval calculations synchronously
> is essential because of unreasonable asynchronously process's executing time D-value, particulayly when add a new path or
> the path's state change down to up.
>
> Please find the up-to-date patch below:
>
> ---
>>From 1a9426dfbad00b5dbefc7020603e40e8896e4869 Mon Sep 17 00:00:00 2001
> From: Yang Feng <philip.yang at huawei.com>
> Date: Mon, 15 May 2017 18:33:29 +0800
> Subject: [PATCH] [dm-devel] [PATCH] multipath-tools:Prioritizer based on a time-delay algorithm
> 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/prioritizers/Makefile | 6 +-
> libmultipath/prioritizers/delayedpath.c | 261 ++++++++++++++++++++++++++++++++
> libmultipath/prioritizers/delayedpath.h | 17 +++
> multipath/multipath.conf.5 | 19 +++
> 4 files changed, 302 insertions(+), 1 deletion(-)
> create mode 100644 libmultipath/prioritizers/delayedpath.c
> create mode 100644 libmultipath/prioritizers/delayedpath.h
>
> diff --git a/libmultipath/prioritizers/Makefile b/libmultipath/prioritizers/Makefile
> index 36b42e4..8df5234 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 ../checkers/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..0490e8d
> --- /dev/null
> +++ b/libmultipath/prioritizers/delayedpath.c
> @@ -0,0 +1,261 @@
> +/*
> + * (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 at huawei.com>
> + * Zou Ming <zouming.zouming at huawei.com>
> + *
> + * This file is released under the GPL.
> + */
> +#include <stdio.h>
> +#include <ctype.h>
> +#include <time.h>
> +
> +#include "debug.h"
> +#include "prio.h"
> +#include "structs.h"
> +#include "../checkers/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 "s"
> +#define CHAR_MSEC "ms"
> +#define CHAR_USEC "us"
> +
> +enum interval_type {
> + INTERVAL_SEC,
> + INTERVAL_MSEC,
> + INTERVAL_USEC,
> + INTERVAL_INVALID
> +};
> +
> +/* interval_unit_str and interval_unit_type keep the same assignment sequence */
> +static const char interval_unit_str[][MAX_CHAR_SIZE] = {
> + CHAR_USEC, CHAR_MSEC, CHAR_SEC
> +};
> +static const int interval_unit_type[] = {
> + INTERVAL_USEC, INTERVAL_MSEC, INTERVAL_SEC
> +};
> +
> +static const 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)
> +{
> + char *p;
> + int size;
> + int i;
> +
> + for (i = 0; i < sizeof(interval_unit_str)/MAX_CHAR_SIZE; i++)
> + {
> + size = strlen(interval_unit_str[i]);
> + p = strstr(source, interval_unit_str[i]);
> + if (p != NULL && p[size] == '|')
> + {
> + memcpy(type, interval_unit_str[i], size+1);
> + return interval_unit_type[i];
> + }
> + }
> +
> + return INTERVAL_INVALID;
> +}
> +
> +/* In multipath.conf, args form: delay_interval|cons_num. For example,
> +* args is "10ms|20", this function can get 10, ms, and 20.
> +*/
> +static int get_digit_and_type(char *args,
> + int *interval,
> + int *consnum,
> + int *type)
> +{
> + char typestr[MAX_CHAR_SIZE];
> + char source[MAX_CHAR_SIZE];
> + char vertica[] = "|";
> + char *tokenbefore = NULL;
> + char *tokenafter = NULL;
> + char *tmp = NULL;
> + unsigned int size = strlen(args);
> +
> + if ((args == NULL) || (interval == NULL)
> + || (consnum == 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, typestr);
> + if (*type == INTERVAL_INVALID)
> + {
> + condlog(0, "delay_interval type is invalid");
> + return 0;
> + }
> +
> + tokenbefore = strtok(source, vertica);
> + tokenafter = strtok(NULL, vertica);
> + typestr[1] = '\0';
> + tokenbefore = strtok(tokenbefore, typestr);
> + if ((tokenbefore == NULL) || (tokenafter == NULL))
> + return 0;
> +
> + tmp = tokenbefore;
> + while (*tmp != '\0')
> + if (!isdigit(*tmp++))
> + {
> + condlog(0, "delay_interval string include invalid char");
> + return 0;
> + }
> +
> + tmp = tokenafter;
> + while (*tmp != '\0')
> + if (!isdigit(*tmp++))
> + {
> + condlog(0, "cons_num string include invalid char");
> + return 0;
> + }
> +
> + *interval = atoi(tokenbefore);
> + *consnum = atoi(tokenafter);
> +
> + return 1;
> +}
> +
> +int check_args_valid(int delay_interval, int cons_num, int type)
> +{
> + if (type == INTERVAL_SEC)
> + {
> + if ((delay_interval < 1) || (delay_interval > 60))
> + {
> + condlog(0, "delay_interval values is invalid");
> + return 0;
> + }
> + }
> + else if (type != INTERVAL_INVALID)
> + {
> + if ((delay_interval < 1) || (delay_interval >= 1000))
> + {
> + condlog(0, "delay_interval values is invalid");
> + return 0;
> + }
> + }
> +
> + if ((cons_num < 3) || (cons_num > 1000))
> + {
> + condlog(0, "cons_num values is invalid");
> + return 0;
> + }
> +
> + return 1;
> +}
> +
> +int get_delay_pref_arg(char *args, int *delay_interval, int *cons_num, int *interval_type)
> +{
> + if (get_digit_and_type(args, delay_interval, cons_num, interval_type) == 0)
> + return 0;
> +
> + if (check_args_valid(*delay_interval, *cons_num, *interval_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 timespec tv;
> +
> + if (pp->fd < 0)
> + return -PRIO_NO_INFORMATION;
> +
> + 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)clock_gettime(CLOCK_MONOTONIC, &tv);
> + before = timeval_to_us(&tv);
> +
> + if (do_readsector0(pp->fd, timeout) == 2)
> + {
> + condlog(0, "%s: path down", pp->dev);
> + return -1;
> + }
> +
> + (void)clock_gettime(CLOCK_MONOTONIC, &tv);
> + after = timeval_to_us(&tv);
> +
> + delay = after - before;
> +
> + 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..d8213e9
> --- /dev/null
> +++ b/libmultipath/prioritizers/delayedpath.h
> @@ -0,0 +1,17 @@
> +#ifndef _DELAYEDPATH_H
> +#define _DELAYEDPATH_H
> +
> +#define PRIO_DELAYED_PATH "delayedpath"
> +
> +#define PRIO_NO_INFORMATION 5
> +
> +#define USEC_PER_SEC 1000000LL
> +#define USEC_PER_MSEC 1000LL
> +#define USEC_PER_USEC 1LL
> +
> +static inline long long timeval_to_us(const struct timespec *tv)
> +{
> + return ((long long) tv->tv_sec * USEC_PER_SEC) + (tv->tv_nsec >> 10);
> +}
> +
> +#endif
> diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
> index 5939688..f1e126e 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: XXs, or XXXus, or XXXms. Unit: Second, or Microsecond, or Millisecond. Valid Values: Integer, s [1, 60], ms [1, 1000), us [1, 1000),
> +For example: 10s, or 100us, or 100ms. The default is: 10ms.
> +.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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