KAMEZAWA Hiroyuki wrote:
But is it too costly that flushing icache page only if a page is newly installed into the system (PG_arch1) && it is mapped as executable ?
Well it was a bit long time ago, I measured on a Tiger box with CPUs of 1.3 GHz: Flushing a page of 64 Kbytes, with modified data in D-cache (it's slower that not having modified data in the D-cache): 13.1 ... 14.7 usec. You may have quicker machines, but having more CPUs or a NUMA architecture can slow it down considerably: - more CPUs have to agree that that's the moment to carry out a flush - NUMA adds delay We may have, say 1 Gbyte / sec local i/o activity (using some RAIDs). Assume a few % of this 1 Gbyte is the program execution, or program swap in. It gives some hundreds of new exec pages / sec => some msec-s can be lost each sec. I can agree that it should not be a big deal :-)
I don't want to leak this (stupid) corner case to the file system layer. Hmm...can't we do clever flushing (like your idea) in VM layer ?
As the VM layer is designed to be independent of the page read in stuff... Thanks, Zoltan - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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