Maxim Yegorushkin wrote:
On Thu, 25 Aug 2005 17:34:59 +0400, Peter Dimov <pdimov@mmltd.net> wrote:
Maxim Yegorushkin wrote:
I just skimmed through boost/detail/quick_allocator.hpp and noticed that quick_allocator causes false sharing on SMP. It happens when several counters are allocated within the same cache line and those counters are used by different processors, thus thrashing processors' cache lines when the counter is written, even when the counter is used by a single processor only.
What do you suggest?
IMO, patching it to avoid false sharing may require too much effort.
That, and it would increase the memory footprint.
Not quite constructive, but I would stick to using standard new/delete and replaced libc provided malloc() with hoard's one for my project.
That's always been the recommended course of action. quick_allocator is for (a) benchmarks that use a horribly slow underlying malloc, (b) people that try the #define and their particular project tends to benefit a lot, and (c) people that want to customize the allocations of their local copy of shared_ptr, but need a starting point. It's very much a "toy" compared to industrial grade malloc replacements, especially in MT mode, where you definitely want thread-specific (or at the very least, lock free) free lists. False sharing is rarely at the top of your worries on high contention SMP. :-)