io read - merged



Hi ,



i have a question regarding to the iostat output:



Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util

sdp 86432.30 0.00 3915.20 2.00 124267.20 2.00 62133.60
1.00 31.72 32.86 8.39 0.26 100.00



According to this output:



rrqm/s : 86432.3 , r/s:3915.2 , rkB/s : 62133.60 .



rrqm/s

The number of read requests merged per sec-

ond that were issued to the device.



The operating system merges multiple io requests into one read call ,
since these io requests are small from the basic io unit.



I have 86432.3 merge per second , with 3915.2 read per second. This
shows that , for 1 read operation , my system does 22 merge
.(86432.3/3915.2) . On the other hand , 62133.60 / 3915.2 = 15kb ,
each read operation issues 15Kb. from the underlying disk subsystem.



15kb/22 merge = 0,6 kb more or less 512b. So each io request in fact is
512byte , but since the minimum io that os can request is 15kb, they
are merged till the 15kb. size is reached.



Are these comments meaningful?



Kind Regards,

tolga

--
redhat-list mailing list
unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/redhat-list

Relevant Pages

  • read merge , read per second
    ... i have a question regarding to the iostat output: ... The operating system merges multiple io requests into one read call, ...
    (linux.redhat)
  • io size , merge and read per second
    ... i have a question regarding to the iostat output: ... The operating system merges multiple io requests into one read call, ...
    (RedHat)
  • RE: What part of z/OS is the OS?
    ... handle all requests from users / other systems... ... intercepts the base error codes and tries its best to send a reasonably ... You don't consider access methods to be part of the operating system? ... We don't have to care, ...
    (bit.listserv.ibm-main)
  • Re: Using Cobol when writing CGIs for the OSU web server.
    ... OSU web server. ... Why do you have that OSU ... This makes requests such as /scr/chocolate.scp to the OAJFOSU decnet ... multiple connections at the same time with threads or ASTs. ...
    (comp.os.vms)
  • Re: Confused about ASP, "sessions", and queuing of multiple requests
    ... cookies (include ASP session state cookie) with the first IE instance. ... and generating multiple HTTP requests from a single IE ... :> running IIS on a multiprocessor server. ...
    (microsoft.public.inetserver.asp.general)