On Fri, Nov 4, 2016 at 12:29 AM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote:
> Oh, okay, the zone lookup. Well I am of the impression that most of the
> cache misses are coming from the waitqueue hash table itself.
No.
Nick, stop this idiocy.
NUMBERS, Nick. NUMBERS.
I posted numbers in "page_waitqueue() considered harmful" on linux-mm.
And quite frankly, before _you_ start posting numbers, that zone crap
IS NEVER COMING BACK.
What's so hard about this concept? We don't add crazy complexity
without numbers. Numbers that I bet you will not be able to provide,
because quiet frankly, even in your handwavy "what about lots of
concurrent IO from hundreds of threads" situation, that wait-queue
will NOT BE NOTICEABLE.
So no "impressions". No "what abouts". No "threaded IO" excuses. The
_only_ thing that matters is numbers. If you don't have them, don't
bother talking about that zone patch.
Linus
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