On 5/31/2017 11:04 AM, Michal Hocko wrote:
Hi Tom,
Hi Michal,
I have stumbled over the following construct in xgbe_map_rx_buffer order = max_t(int, PAGE_ALLOC_COSTLY_ORDER - 1, 0); which looks quite suspicious. Why does it PAGE_ALLOC_COSTLY_ORDER - 1? And why do you depend on PAGE_ALLOC_COSTLY_ORDER at all?
The driver tries to allocate a number of pages to be used as receive buffers. Based on what I could find in documentation, the value of PAGE_ALLOC_COSTLY_ORDER is the point at which order allocations (could) get expensive. So I decrease by one the order requested. The max_t test is just to insure that in case PAGE_ALLOC_COSTLY_ORDER ever gets defined as 0, 0 would be used. I believe there have been some enhancements relative to speed in allocating 0-order pages recently that may make this unnecessary. I haven't run any performance tests yet to determine if I can just go to a 0-order allocation, though. Thanks, Tom
Thanks!
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