#9995 NORM 1.5-sof: optimise kernel write block size

[Zarro Boogs per Child]

#9995: optimise kernel write block size
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           Reporter:  Quozl        |       Owner:  dsaxena                          
               Type:  enhancement  |      Status:  new                              
           Priority:  normal       |   Milestone:  1.5-software-later               
          Component:  kernel       |     Version:  Development build as of this date
         Resolution:               |    Keywords:                                   
        Next_action:  design       |    Verified:  0                                
Deployment_affected:               |   Blockedby:                                   
           Blocking:               |  
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Comment(by dsaxena):

 There are two possible ways to do this that I can think of:

 1) Increase the FS block size to 16K. The disadvantage here is that we are
 adding a lot of overhead to filesystem as all files need a minimum of 16K
 allocated on the disk. An analysis of a fresh install shows that we have
 65914 files that are < 16K in size and we would allocate an extra 176348
 4K blocks (688 MiB) just due to the overhead. Not acceptable. One
 different possibility is to break up the system into further partitions
 and have the install be on a 4K block size and /home/olpc be on 16K so
 that user writes go faster; however, we need some data on average user
 data file sizes to ensure we're not again wasting disk space.

 2) Look at/modify the elevator code or the mmblock code itself to ensure
 that we are grouping writes into 16K chunks when possible.

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Ticket URL: <http://dev.laptop.org/ticket/9995#comment:1>
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