Messages in this thread | | | Date | Sun, 29 Aug 2004 13:25:43 -0700 | From | William Lee Irwin III <> | Subject | Re: [BENCHMARK] nproc: netlink access to /proc information |
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On Sun, 29 Aug 2004 12:17:07 -0700, William Lee Irwin III wrote: >> Introducing another whole-tasklist scan, even if feasible, is probably >> not a good idea.
On Sun, Aug 29, 2004 at 09:49:26PM +0200, Roger Luethi wrote: > I'm not sure whether I should participate in that discussion. I'll risk > discrediting nproc with wild speculations on a subject I haven't really > looked into yet. Ah well...
There isn't much to speculate about here; reducing the arrival rate to tasklist_lock is okay, but it can't be held forever or use unbounded allocations or anything like that.
On Sun, Aug 29, 2004 at 09:49:26PM +0200, Roger Luethi wrote: > As far as nproc (and process monitoring) is concerned, we aren't really > interested in walking a complete process list. All we care about is > which pids exist right now. How about a bit field, maintained by the > kernel, to indicate for each pid whether it exists or not? This would > amount to 4 KiB by default and 512 KiB for PID_MAX_LIMIT (4 million > processes). Maintenance cost would be one atomic bit operation per > process creation/deletion. No contested locks. > The list for the nproc user could be prepared based on the bit field > (or simply memcpy'd), no tasklist_lock or walking linked lists required. > What am I missing?
The pid bitmap could be exported to userspace rather easily.
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