Re: Readahead value 128K? (was Re: Drastic Slowdown of 'fseek()' Calls From 2.4 to 2.6 -- VMM Change?)

[Linda Walsh <lkml@tlinx.org>]

Marr wrote:
> On Sunday 05 March 2006 6:02pm, Linda Walsh wrote:
>> Does this happen with a seek call as well, or is this limited
>> to fseek?
>>
>> if you look at "hdparm's" idea of read-ahead, what does it say
>> for the device?.  I.e.:
>>
>> hdparm /dev/hda:
>>
>> There is a line entitled "readahead".  What does it say?
>
> Linda,
>
> I don't know (based on your email addressing) if you were directing this 
> question at me, but since I'm the guy who originally reported this issue, 
> here are my 'hdparm' results on my (standard Slackware 10.2) ReiserFS 
> filesystem:
>
>    2.6.13 (with 'nolargeio=1' for reiserfs mount): 
>       readahead    = 256 (on)
>
>    2.6.13 (without 'nolargeio=1' for reiserfs mount): 
>       readahead    = 256 (on)
>
>    2.4.31 ('nolargeio' option irrelevant/unavailable for 2.4.x): 
>       readahead    = 8 (on)
>
> *** Please CC: me on replies -- I'm not subscribed.
>
> Regards,
> Bill Marr
--------
    Could you retry your test with read-ahead set to a smaller
value?  Say the same as in 2.4 (8) or 16 and see if that changes
anything?

hdparm -a8 /dev/hdx
  or
hdparm -a16 /dev/hdx