#10935 LOW Not Tri: XO-1.75 A2 over XO-1.5 external SD via cache performance regression

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#10935: XO-1.75 A2 over XO-1.5 external SD via cache performance regression
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 Reporter:  Quozl         |                 Owner:               
     Type:  defect        |                Status:  new          
 Priority:  low           |             Milestone:  Not Triaged  
Component:  not assigned  |               Version:  not specified
 Keywords:                |           Next_action:  never set    
 Verified:  0             |   Deployment_affected:               
Blockedby:                |              Blocking:               
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 Comparing filesystem I/O rates to external SD between XO-1.75 A2 os6 and
 XO-1.5 os20.

  * XO-1.75 A2 is almost twice as fast as XO-1.5 for read of /dev/urandom.
  * XO-1.75 is slightly faster than XO-1.5 for read of external SD
 bypassing cache (using O_DIRECT).
  * XO-1.75 is almost half as fast as XO-1.5 for read of external SD via
 cache.

 A test program derived from runin-sdwrite reads 4MB from /dev/urandom,
 writes bypassing cache to a file, copies the file bypassing cache, then
 reads the file eight times bypassing cache, then reads the file another
 eight times through cache.  The program was run on the same external SD
 card, an ADATA microSDHC class 2 size 4GB.

 || '''XO-1.5 os20''' || '''XO-1.75 os6''' ||
 || ur 5.8 (5.49 Mbps) || ur 3.1 (10.49 Mbps) ||
 || wr 9.8 (3.26 Mbps) || wr 7.7 (4.17 Mbps) ||
 || cp 7.7 (4.14 Mbps) || cp 6.7 (4.76 Mbps) ||
 || cmp 3.3 (19.67 Mbps) O_DIRECT || cmp 2.8 (23.25 Mbps) O_DIRECT ||
 || cmp 3.3 (19.31 Mbps) O_DIRECT || cmp 2.7 (23.54 Mbps) O_DIRECT ||
 || cmp 3.3 (19.58 Mbps) O_DIRECT || cmp 2.8 (23.14 Mbps) O_DIRECT ||
 || cmp 3.3 (19.49 Mbps) O_DIRECT || cmp 2.8 (23.22 Mbps) O_DIRECT ||
 || cmp 3.3 (19.58 Mbps) O_DIRECT || cmp 2.8 (22.93 Mbps) O_DIRECT ||
 || cmp 3.3 (19.56 Mbps) O_DIRECT || cmp 2.8 (23.05 Mbps) O_DIRECT ||
 || cmp 3.3 (19.64 Mbps) O_DIRECT || cmp 2.8 (22.98 Mbps) O_DIRECT ||
 || cmp 3.3 (19.43 Mbps) O_DIRECT || cmp 2.8 (22.77 Mbps) O_DIRECT ||
 || cmp 0.7 (91.21 Mbps)  || cmp 0.8 (76.14 Mbps)  ||
 || cmp 0.1 (1078.39 Mbps)  || cmp 0.1 (578.81 Mbps)  ||
 || cmp 0.1 (1101.70 Mbps)  || cmp 0.1 (630.35 Mbps)  ||
 || cmp 0.1 (1105.52 Mbps)  || cmp 0.1 (585.45 Mbps)  ||
 || cmp 0.1 (1109.13 Mbps)  || cmp 0.1 (585.03 Mbps)  ||
 || cmp 0.1 (1107.00 Mbps)  || cmp 0.1 (587.57 Mbps)  ||
 || cmp 0.1 (1099.66 Mbps)  || cmp 0.1 (615.77 Mbps)  ||
 || cmp 0.1 (1108.05 Mbps)  || cmp 0.1 (616.08 Mbps)  ||

 Test program to be attached.

-- 
Ticket URL: <http://dev.laptop.org/ticket/10935>
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