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SubjectRe: [patch] voluntary-preempt-2.6.9-rc3-mm3-T3
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On Thu, 2004-10-07 at 06:52, Ingo Molnar wrote:
> i've released the -T3 VP patch:
>
> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.9-rc3-mm3-T3
>

[adding Andrew Morton to the cc: list as these issues are increasingly
relevant to -mm and not VP specific]

I am seeing the same prune_icache latency that Mark reported. I have
never seen this one at all before T3. This one seem very frequent,
enough so to overtake the netif_skb single-packet processing latency
that seems to be our lower bound.

preemption latency trace v1.0.7 on 2.6.9-rc3-mm3-VP-T3
-------------------------------------------------------
latency: 242 us, entries: 178 (178) | [VP:1 KP:1 SP:1 HP:1 #CPUS:1]
-----------------
| task: kswapd0/54, uid:0 nice:0 policy:0 rt_prio:0
-----------------
=> started at: prune_icache+0x52/0x460
=> ended at: prune_icache+0x162/0x460
=======>
00000001 0.000ms (+0.001ms): prune_icache (shrink_icache_memory)
00000001 0.001ms (+0.002ms): inode_has_buffers (prune_icache)
00000001 0.004ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.005ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.007ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.008ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.010ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.011ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.012ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.014ms (+0.001ms): inode_has_buffers (prune_icache)
00000001 0.015ms (+0.001ms): inode_has_buffers (prune_icache)
[more of same interrupted by the timer a few times]

Workload is just a kernel compile and an RT task (jackd).
Interestingly, kswapd seems to have triggered the above, but I should
not be hitting swap! I have swappiness set to 0, and here is what
vmstat showed:

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 4 30608 54476 221680 0 0 9 12 310 600 36 8 56 0
1 0 4 41424 54476 221796 0 0 0 0 1109 2577 88 12 0 0
1 0 4 41168 54484 221808 0 0 24 0 1005 2158 83 17 0 0
1 0 4 34704 54496 221808 0 0 0 192 1015 2063 92 8 0 0
1 0 4 32208 54496 221808 0 0 0 0 1003 2045 96 4 0 0
1 0 4 30928 54496 221808 0 0 0 0 1004 2090 98 2 0 0
Lee

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