Messages in this thread | | | Subject | Re: [RFC PATCH] mm: page_alloc: High-order per-cpu page allocator | From | Vlastimil Babka <> | Date | Thu, 24 Nov 2016 08:26:39 +0100 |
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On 11/23/2016 05:33 PM, Mel Gorman wrote: >>> + >>> +static inline unsigned int pindex_to_order(unsigned int pindex) >>> +{ >>> + return pindex < MIGRATE_PCPTYPES ? 0 : pindex - MIGRATE_PCPTYPES + 1; >>> +} >>> + >>> +static inline unsigned int order_to_pindex(int migratetype, unsigned int order) >>> +{ >>> + return (order == 0) ? migratetype : MIGRATE_PCPTYPES - 1 + order; >> >> Here I think that "MIGRATE_PCPTYPES + order - 1" would be easier to >> understand as the array is for all migratetypes, but the order is shifted? >> > > As in migratetypes * costly_order ? That would be excessively large.
No, I just meant that instead of "MIGRATE_PCPTYPES - 1 + order" it could be "MIGRATE_PCPTYPES + order - 1" as we are subtracting from order, not migratetypes. Just made me confused a bit when seeing the code for the first time.
>>> @@ -1083,10 +1083,12 @@ static bool bulkfree_pcp_prepare(struct page *page) >>> * pinned" detection logic. >>> */ >>> static void free_pcppages_bulk(struct zone *zone, int count, >>> - struct per_cpu_pages *pcp) >>> + struct per_cpu_pages *pcp, >>> + int migratetype) >>> { >>> - int migratetype = 0; >>> - int batch_free = 0; >>> + unsigned int pindex = 0; >> >> Should pindex be initialized to migratetype to match the list below? >> > > Functionally it doesn't matter. It affects which list is tried first if > the preferred list is empty. Arguably it would make more sense to init > it to NR_PCP_LISTS - 1 so all order-0 lists are always drained before the > high-order pages but there is not much justification for that.
OK
> I'll take your suggestion until there is data supporting that high-order > caches should be preserved. > > Thanks. >
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