>>> The Lee-Man <[email protected]> schrieb am 16.04.2018 um 23:57 in
Nachricht <[email protected]>:
> On Monday, April 16, 2018 at 2:38:01 PM UTC-7, The Lee-Man wrote:
>>
>> On Friday, April 13, 2018 at 3:19:11 PM UTC-7, [email protected]
>> wrote:
>>>
>>> From: Cathy Zhou <[email protected]>
>>>
>>> iscsi boot performance can be improved by sleep() with finer
>>> grained interval and exponential backoff.
>>>
>>> Signed-off-by: Cathy Zhou <[email protected]>
>>> ---
>>> usr/iscsistart.c | 35 ++++++++++++++++++++++++-----------
>>> 1 file changed, 24 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/usr/iscsistart.c b/usr/iscsistart.c
>>> index 67ac475..1e77e40 100644
>>> --- a/usr/iscsistart.c
>>> +++ b/usr/iscsistart.c
>>> @@ -27,6 +27,7 @@
>>> #include <unistd.h>
>>> #include <string.h>
>>> #include <signal.h>
>>> +#include <time.h>
>>> #include <sys/mman.h>
>>> #include <sys/utsname.h>
>>> #include <sys/signal.h>
>>> @@ -224,7 +225,8 @@ static int login_session(struct node_rec *rec)
>>> {
>>> iscsiadm_req_t req;
>>> iscsiadm_rsp_t rsp;
>>> - int rc, retries = 0;
>>> + int rc, msec, err;
>>> + struct timespec ts;
>>>
>>> rc = apply_params(rec);
>>> if (rc)
>>> @@ -237,18 +239,29 @@ static int login_session(struct node_rec *rec)
>>> req.command = MGMT_IPC_SESSION_LOGIN;
>>> memcpy(&req.u.session.rec, rec, sizeof(*rec));
>>>
>>> -retry:
>>> - rc = iscsid_exec_req(&req, &rsp, 0, ISCSID_REQ_TIMEOUT);
>>> /*
>>> - * handle race where iscsid proc is starting up while we are
>>> - * trying to connect.
>>> + * Need to handle race where iscsid proc is starting up while we
>>> are
>>> + * trying to connect. Retry with exponential backoff, start from
>>> 50 ms.
>>> */
>>> - if (rc == ISCSI_ERR_ISCSID_NOTCONN && retries < 30) {
>>> - retries++;
>>> - sleep(1);
>>> - goto retry;
>>> - } else if (rc)
>>> - iscsi_err_print_msg(rc);
>>> + for (msec = 50; msec <= 15000; msec <<= 1) {
>>>
>>
>> Why are you using 50 -> 15000? Isn't the sequence then going to be:
>> -> 50
>> -> 100
>> -> 200
>> -> 400
>> -> 800
>> -> 1600 (too large)
>>
>> So why not either go to 800 or to 1600?
>>
>>
> Doh! I am off by a factor of 10!
>
> -> 3200, 6400, 12800
I'm late in the discussion, but I'd vote for three things:
1) Make the limits configurable (first delay, maximum wait duration)
2) Change the algorithm not to specify the last delay being used, but the total
amount of waiting
3) Log if waiting for some longer time
I had implemented something like that years ago in Perl. Maybe to make it
clearer what I'm thinking of, here's a code snipplet:
$self->Log(0, 'D', $logger, "Waiting up to $limit seconds for condition")
if ($verbosity > 1 && !$result);
no integer;
for (my $wait = $min_wait; !$result && $limit > 0;
$limit -= $wait, $wait *= 2) {
$wait = $limit
if ($wait > $limit);
$self->Log(1, 'D', $logger,
"Waiting $wait (of $limit remaining) seconds")
if ($verbosity > 0 && !$result);
# sleep $wait seconds to allow condition to become true
select(undef, undef, undef, $wait);
$result = $condition_r->($self);
}
$self->Log(1, 'D', $logger, "$condition_txt with $limit seconds remaining")
if ($verbosity > 0 && $result);
[...]
Regards,
Ulrich
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