Messages in this thread | | | Date | Sat, 19 Oct 2002 22:52:29 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] ipv4: only produce one record in fib_seq_show |
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"David S. Miller" wrote: > > .. > kernel/timer.c's main data structures desperately want to be per-cpu > or allocated at boot time also. It, as has been noted often on this > list, is actually more bloat than the ipv4 statistics stuff. :-)
I have a bunch of patches under test which do that.
The tricky bit is that at present, the per-cpu data for all 32 CPUs is always allocated. We had to change that to only allocate the secondary CPU's memory when the CPU is coming up.
This means that:
for (i = 0; i < NR_CPUS; i++) play_with(per_cpu(something, i));
becomes a bug. Because the per-cpu memory for not-possible CPUs is not allocated. I created a `for_each_possible_cpu(i)' helper macro for that.
Another issue:
/* this is basically for_each_possible_cpu() */ for (i = 0; i < NR_CPUS; i++) { if (cpu_possible(i)) { play_with(per_cpu(something, i)); } }
the above code will fail if it is run before smp_init(), because smp_init() sets up cpu_callout_map() and the per-cpu memory. We (Dipanker and I) fixed up all the callers.
The code works OK, on ia32. But we think ia64 needs more work.
That's 128k saved. There's another 128k-odd in a huge hashtable in kernel/pid.c (even on uniprocessor) which needs a diet. Also 80k or so in runqueues. The runqueues are set up before smp_init(), but I expect a cpu notifier and some reorg there will work. Haven't done sched.c yet.
I suspect we waste more memory than this in dynamically allocated hashtables and mempools though. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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