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Re: What on Earth is JFFS2 GC doing?





Vipin.Malik@xxxxxxx.com said:
>  22909.981000 ms   22809.981000 ms!<Profile saved in
> file:JitterTest.profilesnap-5>

> [root@xxxxxxx.profilesnap-5 -m
> /boot/linux-2.4.1-JFFS2.System.map
>      4 startup_32                                 0.0127
>      1 printk                                     0.0024
>      1 get_unused_buffer_head                     0.0069
>      2 write_profile                              0.0417
>      3 cfi_amdstd_erase_onesize                   0.0031
>      3 physmap_read32                             0.0938
>      2 __generic_copy_to_user                     0.0312
>      1 __generic_copy_from_user                   0.0156
>     17 total                                      0.0000

Am I interpreting the above correctly? During the 22.9-second period it 
took to perform that write, there were a total of 17 timer ticks?


> After the suggested patch. Not much diffrence. I even got a 22seconds
> jitter! However the # of ticks for the suspect routine has gone *way*
> down. 

I didn't expect the jitter to go away.

You're still garbage-collecting a whole 256KiB block in the timeslice of 
the unlucky write, rather than doing a little bit each time. That's a 
separate problem.

I did expect the worst case times to get a lot better though - 22 seconds is
better than 60. If the numbers still look like that after enough
iterations to reasonably draw a conclusion, I'll commit that patch.

--
dwmw2



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