#10112 NORM Not Tri: GUI freezes on fsync

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#10112: GUI freezes on fsync
---------------------------+------------------------------------------------
 Reporter:  jon.nettleton  |                 Owner:                                   
     Type:  defect         |                Status:  new                              
 Priority:  normal         |             Milestone:  Not Triaged                      
Component:  not assigned   |               Version:  Development build as of this date
 Keywords:                 |           Next_action:  never set                        
 Verified:  0              |   Deployment_affected:                                   
Blockedby:                 |              Blocking:                                   
---------------------------+------------------------------------------------
 Using firefox from the GNOME desktop you find that there are frequent GUI
 freezes, no clicking, no screen refresh etc.  After running

 {{{
 strace -p $(pgrep firefox) -e fsync,fdatasync -tT
 }}}

 it became obvious that we are suffering from long fsync writes to the
 filesystem.  I then installed the same OS v119  to a high speed external
 SDHC card and moved the olpc home directory over to it.  This should give
 the exact same firefox sqlite databases and information.  I found the
 fsync's to be virtually un-noticable.  Here are the two datasets, I tried
 to mimic the testing to be the same in each instance.


 {{{
 Internal SD Card:

 17:51:28 fdatasync(62)                  = 0 <3.099224>
 17:51:31 fdatasync(62)                  = 0 <0.450451>
 17:51:32 fdatasync(31)                  = 0 <0.519231>
 17:51:35 fsync(57)                      = 0 <3.760307>
 17:51:50 fsync(83)                      = 0 <5.421490>
 17:52:05 fsync(54)                      = 0 <0.460336>
 17:52:16 fsync(70)                      = 0 <2.439097>
 17:52:18 fdatasync(62)                  = 0 <0.036100>
 17:52:19 fdatasync(62)                  = 0 <0.006095>
 17:52:19 fdatasync(31)                  = 0 <0.872539>
 17:52:29 fsync(54)                      = 0 <3.460910>
 17:52:42 fsync(54)                      = 0 <0.440038>
 17:53:19 fsync(77)                      = 0 <0.461735>
 17:53:22 fsync(81)                      = 0 <3.364934>
 17:53:35 fsync(63)                      = 0 <3.332061>
 17:53:49 fsync(55)                      = 0 <0.018636>
 17:54:00 fsync(53)                      = 0 <0.014304>
 18:01:37 fsync(18)                      = 0 <1.332728>
 18:01:48 fsync(63)                      = 0 <0.856377>

 }}}


 {{{
 External SDHC

 17:46:54 fsync(46)                      = 0 <0.020497>
 17:47:15 fsync(62)                      = 0 <0.176407>
 17:47:19 fdatasync(60)                  = 0 <0.332567>
 17:47:19 fdatasync(60)                  = 0 <0.163582>
 17:47:20 fdatasync(24)                  = 0 <0.270497>
 17:47:25 fsync(57)                      = 0 <0.166996>
 17:47:32 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:47:34 fdatasync(60)                  = 0 <1.356135>
 17:47:35 fdatasync(60)                  = 0 <0.004512>
 17:47:35 fdatasync(24)                  = 0 <0.209471>
 17:47:39 fsync(82)                      = 0 <0.288864>
 17:47:50 fsync(83)                      = 0 <0.180585>
 17:47:53 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:47:53 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:47:53 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:47:55 fdatasync(60)                  = 0 <0.014631>
 17:47:56 fdatasync(60)                  = 0 <0.002435>
 17:47:56 fdatasync(24)                  = 0 <0.137674>
 17:48:00 fsync(83)                      = 0 <0.442724>
 17:48:11 fsync(67)                      = 0 <0.308368>
 17:48:11 fdatasync(60)                  = 0 <0.176889>
 17:48:11 fdatasync(60)                  = 0 <0.002327>
 17:48:11 fdatasync(24)                  = 0 <0.311335>
 17:48:12 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:48:13 --- SIGCHLD (Child exited) @ 0 (0) ---
 17:48:21 fsync(68)                      = 0 <0.178435>
 17:48:31 fsync(37)                      = 0 <0.170102>
 }}}

 Obviously there are two big differences 1 the speed difference, but
 secondly the SIGCHLD's.  I am not sure what caused them but I am
 disregarding them temporarily.

 My external SDHC card is a class 6 card.  I decided to check performance
 as I don't know what the internal card is.  Running hdparm -Tt ( I know it
 is a horrible benchmark, but I haven't gotten that far into this problem
 yet ) I actually found the buffered and unbuffered read speeds to be quite
 similar.  This doesn't help with the write speed benchmarking needed for
 fsync's but it showed there wasn't a horribly obvious performance
 difference between the cards.

 I will update this bug with more information after write speeds are
 tested.

-- 
Ticket URL: <http://dev.laptop.org/ticket/10112>
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