This series is in need of Tested-by's and some reviewing before it can be pushed anywhere. The performance of the tests I ran were not sensitive to the premature reclaim of buffer pages although I was able to show the average age of buffer pages is now higher as expected. Also note the comments I make about the average age of file pages versus buffer pages at the end of this mail that I'd like filesystem people to think about. Changelog since V1 o Add tracepoint to model age of page types (mel) Andrew Perepechko reported a problem whereby pages are being prematurely evicted as the mark_page_accessed() hint is ignored for pages that are currently on a pagevec -- http://www.spinics.net/lists/linux-ext4/msg37340.html . Alexey Lyahkov and Robin Dong have also reported problems recently that could be due to hot pages reaching the end of the inactive list too quickly and be reclaimed. Rather than addressing this on a per-filesystem basis, this series aims to fix the mark_page_accessed() interface by deferring what LRU a page is added to pagevec drain time and allowing mark_page_accessed() to call SetPageActive on a pagevec page. Patch 1 adds two tracepoints for LRU page activation and insertion. Using these processes it's possible to build a model of pages in the LRU that can be processed offline. Patch 2 defers making the decision on what LRU to add a page to until when the pagevec is drained. Patch 3 searches the local pagevec for pages to mark PageActive on mark_page_accessed. The changelog explains why only the local pagevec is examined. Patch 4 tidies up the API. postmark, a dd-based test and fs-mark both single and threaded mode were run but none of them showed any performance degradation or gain as a result of the patch. Using patch 1, I built a *very* basic model of the LRU to examine offline what the average age of different page types on the LRU were in milliseconds. Of course, capturing the trace distorts the test as it's written to local disk but it does not matter for the purposes of this test. The average age of pages in milliseconds were vanilla deferdrain Average age mapped anon: 1454 1855 Average age mapped file: 127841 143755 Average age unmapped anon: 85 157 Average age unmapped file: 73633 39368 Average age unmapped buffers: 74054 116636 The LRU activity was mostly files which you'd expect for a dd-based workload. Note that the average age of buffer pages is increased by the series and it is expected this is due to the fact that the buffer pages are now getting added to the active list when drained from the pagevecs. Note that the average age of the unmapped file data is decreased as they are still added to the inactive list and are reclaimed before the buffers. There is no guarantee this is a universal win for all workloads and it would be nice if the filesystem people gave some thought as to whether this decision is generally a win or a loss. fs/cachefiles/rdwr.c | 30 ++++---------- fs/nfs/dir.c | 7 +--- include/linux/pagevec.h | 34 +--------------- include/trace/events/pagemap.h | 89 ++++++++++++++++++++++++++++++++++++++++++ mm/swap.c | 82 +++++++++++++++++++++++++------------- 5 files changed, 154 insertions(+), 88 deletions(-) create mode 100644 include/trace/events/pagemap.h -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
