Messages in this thread | | | Date | Fri, 1 May 2009 13:05:50 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH mmotm] mm: alloc_large_system_hash check order |
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On Fri, 1 May 2009, Eric Dumazet wrote: > Hugh Dickins a écrit : > > On Thu, 30 Apr 2009, Mel Gorman wrote: > >> On Wed, Apr 29, 2009 at 10:09:48PM +0100, Hugh Dickins wrote: > >>> On an x86_64 with 4GB ram, tcp_init()'s call to alloc_large_system_hash(), > >>> to allocate tcp_hashinfo.ehash, is now triggering an mmotm WARN_ON_ONCE on > >>> order >= MAX_ORDER - it's hoping for order 11. alloc_large_system_hash() > >>> had better make its own check on the order. > > Well, I dont know why, since alloc_large_system_hash() already take > care of retries, halving size between each tries.
Sorry, I wasn't clear: I just meant that if we keep that WARN_ON_ONCE(order >= MAX_ORDER) in __alloc_pages_slowpath(), then we need alloc_large_system_hash() to avoid the call to __get_free_pages() in the order >= MAX_ORDER case, precisely because we're happy with the way it halves and falls back, so don't want a noisy warning; and now that we know that it could give that warning, it would be a shame for the _ONCE to suppress more interesting warnings later.
I certainly did not mean for alloc_large_system_hash() to fail in the order >= MAX_ORDER case, nor did the patch do so.
Hugh | |