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SubjectRe: [PATCH 38/40] perf session: Handle index files generally
On 5/17/15 6:30 PM, Namhyung Kim wrote:
> The current code assumes that the number of index item and cpu are
> matched so it creates that number of threads. But it's not the case
> of non-system-wide session or data came from different machine.
>
> Just creates threads at most number of online cpus and process data.

-----8<-----

> @@ -1717,6 +1742,7 @@ int perf_session__process_events_mt(struct perf_session *session, void *arg)
> int err, i, k;
> int nr_index = session->header.nr_index;
> u64 size = perf_data_file__size(file);
> + int nr_thread = sysconf(_SC_NPROCESSORS_ONLN);

It's not clear to me how this multi-threaded perf is going to work on
large systems especially this patch if a system has holes in the active
cpus. e.g,

# lscpu
Architecture: sparc64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Big Endian
CPU(s): 704
On-line CPU(s) list:
32-63,128-223,256-351,384-479,576-831,864-927,960-1023
Thread(s) per core: 12
Core(s) per socket: 18
Socket(s): 3
NUMA node(s): 4
NUMA node0 CPU(s): 32-63,128-223
NUMA node1 CPU(s): 256-351,384-479
NUMA node2 CPU(s): 576-767
NUMA node3 CPU(s): 768-831,864-927,960-1023

So you are going to spawn 704 threads? Each thread handles a per-cpu buffer?

yes, I still need to find time to take if for a test drive; maybe by the
end of the week.

David

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