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I just found out there's no pdflush on my Linux, v2.6.38. But when I do a

ps uax | grep flush

It shows:

root       269  0.1  0.0      0     0 ?        S    13:05   0:04 [flush-8:0]

My kernel is:

Linux yonggang-laptop 2.6.38-11-generic #50-Ubuntu SMP Mon Sep 12 21:18:14 UTC 2011 i686 i686 i386 GNU/Linux

It seems [flush8:0] is a replacement of pdflush. Does anyone have further information about how this [flush-8:0] thread works and what does 8:0 mean? I know in old versions, the number of pdflush threads is 2-8 and it varies upon the system write back workload. I expect the [flush-8:0] thread to do something similar. In addition, why does /proc/sys/vm/nr_pdflush_threads still exist if there's no pdflush thread at all?

Thanks,

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1 Answer 1

up vote 2 down vote accepted

The flush process is responsible for flushing data from temporary disk to permanent. Its a replacement for the old pdflush, like you mentioned, that claims much faster response time. The numbers you see refer to the block device it is monitoring.

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Thank you very much for your answer. 8:0 corresponds to /sys/class/block/sda/dev on my computer, so this flush process should be working for the device /dev/sda. I get one more question: since the write back process is changed, does dirty_ratio and dirty_background_ratio still work in the same way as before? –  yonggang Nov 7 '11 at 20:00
    
I would say with 99% certainty that yes, they are still used and respected. Because these settings exist in the /proc/sys framework, they would likely be removed if they were not used. –  Andrew M. Nov 7 '11 at 21:54
    
It makes sense. Thank you for your reply. –  yonggang Nov 7 '11 at 23:59

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