> My test results:
>
> The 4xCPU 2.3.11 kernel performs about 6-8% faster than the 2.2.10 kernel at
> the highest loads. The 2.3.11 kernel did almost 3x the number of spinlocks-
> per-second vs. the 2.2.10 kernel, due to the finer granularity of 2.3's
> locking schemes, but 2.3 exhibits lock contention on only 2% of these calls
> vs. 18% in 2.2. When 2.3 does contend, the mean wait-times are almost 2x
> those in 2.2. One possible hypothesis for the longer mean wait-times is
> that 2.3 has eliminated the quick, trivial contentions, leaving the longer
> contentions to raise the mean.
>
> With this workload on this 4xCPU Xeon hardware, spinlock contention in
> 2.2.10 consumed about 8% of theoretically available CPU cycles (340
> millisecs/sec of waiting out of the 4,000 millisecs/sec theoretically
> available) vs. about 2% in 2.3.11 (95 millisecs of waiting out of 4,000
> millisecs).
>
> The kernel_flag usage is still significant in 2.3, but its contention is
> greatly reduced. [...]
have you checked out 2.3.18/19 already? Compared to 2.3.11 it has fully
threaded VFS, buffer-cache and VM, this should further cut down on
kernel_flag usage. I suspect it should be well below 1% already.
-- mingo
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