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path: root/tools/perf/bench/mem-memcpy-x86-64-asm.S

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ver, in most cases, the fadvise happens from the same context that instantiated the pages, and any pre-LRU pages in the specified range are most likely sitting on the local CPU's LRU cache, and so in many cases this results in unnecessary remote calls, which, in a loaded system, can hold up the fadvise() call significantly. [ I didn't record it in the extreme case we observed at Facebook, unfortunately. We had a slow-to-respond system and noticed it lru_add_drain_all() leading the profile during fadvise calls. This patch came out of thinking about the code and how we commonly call FADV_DONTNEED. FWIW, I wrote a silly directory tree walker/searcher that recurses through /usr to read and FADV_DONTNEED each file it finds. On a 2 socket 40 ht machine, over 1% is spent in lru_add_drain_all(). With the patch, that cost is gone; the local drain cost shows at 0.09%. ] Try to avoid the remote call by flushing the local LRU cache before even attempting to invalidate anything. It's a cheap operation, and the local LRU cache is the most likely to hold any pre-LRU pages in the specified fadvise range. Link: http://lkml.kernel.org/r/20161214210017.GA1465@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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