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Subjectsystem stops sending IOs for long time
Hi,
I have a performance issue with my system that runs samba server, once
in a while (6 seconds) I see that the throughput falls almost to to
zero when doing read for large file. I'm running kernel 2.6.22.10. I
don't see this issue when using kernel 2.6.12.

when observing the activity leds on my sata controller, I see that it
get off for about 1 second meaning no commands sent to the HDD for
that long time. I used the blktrace in order to have a look into the
IOs, and found that the system really stops sending commands for long
periods, here is the section of the blkparse that shows this problem:
8,2 0 12747 5.550000000 328 D R 108068834 + 512 [smbd]
8,2 0 12748 5.550000000 328 D R 108069346 + 512 [smbd]
8,2 0 12749 5.550000000 328 D R 108069858 + 512 [smbd]
8,2 0 12750 5.550000000 328 D R 108070370 + 512 [smbd]
8,2 0 12751 5.550000000 328 U N [smbd] 5
8,2 0 12752 5.550000000 0 C R 108068834 + 512 [0]
8,2 0 12753 5.560000000 0 C R 108069346 + 512 [0]
8,2 0 12754 5.570000000 0 C R 108069858 + 512 [0]
8,2 0 12755 5.570000000 0 C R 108070370 + 512 [0]
8,2 0 12756 6.570000000 0 C R 108066786 + 512 [0]
8,2 0 12757 6.590000000 328 Q R 108070882 + 8 [smbd]
8,2 0 12758 6.590000000 328 G R 108070882 + 8 [smbd]
8,2 0 12759 6.590000000 328 P N [smbd]
8,2 0 12760 6.590000000 328 I R 108070882 + 8 [smbd]
8,2 0 12761 6.590000000 328 Q R 108070890 + 8 [smbd]
8,2 0 12762 6.590000000 328 M R 108070890 + 8 [smbd]

any idea how to fix this issue?
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