mm: pagemap: avoid unnecessary overhead when tracepoints are deactivated

commit 24b7e5819ad5cbef2b7c7376510862aa8319d240 upstream.

This was formerly the series "Improve sequential read throughput" which
noted some major differences in performance of tiobench since 3.0.
While there are a number of factors, two that dominated were the
introduction of the fair zone allocation policy and changes to CFQ.

The behaviour of fair zone allocation policy makes more sense than
tiobench as a benchmark and CFQ defaults were not changed due to
insufficient benchmarking.

This series is what's left.  It's one functional fix to the fair zone
allocation policy when used on NUMA machines and a reduction of overhead
in general.  tiobench was used for the comparison despite its flaws as
an IO benchmark as in this case we are primarily interested in the
overhead of page allocator and page reclaim activity.

On UMA, it makes little difference to overhead

          3.16.0-rc3   3.16.0-rc3
             vanilla lowercost-v5
User          383.61      386.77
System        403.83      401.74
Elapsed      5411.50     5413.11

On a 4-socket NUMA machine it's a bit more noticable

          3.16.0-rc3   3.16.0-rc3
             vanilla lowercost-v5
User          746.94      802.00
System      65336.22    40852.33
Elapsed     27553.52    27368.46

This patch (of 6):

The LRU insertion and activate tracepoints take PFN as a parameter
forcing the overhead to the caller.  Move the overhead to the tracepoint
fast-assign method to ensure the cost is only incurred when the
tracepoint is active.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/include/trace/events/pagemap.h b/include/trace/events/pagemap.h
index 1c9fabde69e4bb4aa5f13bc23a3b0d374549bbb6..ce0803b8d05f340f42116c1f129d08a645344e23 100644 (file)
--- a/include/trace/events/pagemap.h
+++ b/include/trace/events/pagemap.h
@@ -28,12 +28,10 @@ TRACE_EVENT(mm_lru_insertion,
 
        TP_PROTO(
                struct page *page,
-               unsigned long pfn,
-               int lru,
-               unsigned long flags
+               int lru
        ),
 
-       TP_ARGS(page, pfn, lru, flags),
+       TP_ARGS(page, lru),
 
        TP_STRUCT__entry(
                __field(struct page *,  page    )
@@ -44,9 +42,9 @@ TRACE_EVENT(mm_lru_insertion,
 
        TP_fast_assign(
                __entry->page   = page;
-               __entry->pfn    = pfn;
+               __entry->pfn    = page_to_pfn(page);
                __entry->lru    = lru;
-               __entry->flags  = flags;
+               __entry->flags  = trace_pagemap_flags(page);
        ),
 
        /* Flag format is based on page-types.c formatting for pagemap */
@@ -64,9 +62,9 @@ TRACE_EVENT(mm_lru_insertion,
 
 TRACE_EVENT(mm_lru_activate,
 
-       TP_PROTO(struct page *page, unsigned long pfn),
+       TP_PROTO(struct page *page),
 
-       TP_ARGS(page, pfn),
+       TP_ARGS(page),
 
        TP_STRUCT__entry(
                __field(struct page *,  page    )
@@ -75,7 +73,7 @@ TRACE_EVENT(mm_lru_activate,
 
        TP_fast_assign(
                __entry->page   = page;
-               __entry->pfn    = pfn;
+               __entry->pfn    = page_to_pfn(page);
        ),
 
        /* Flag format is based on page-types.c formatting for pagemap */

diff --git a/mm/swap.c b/mm/swap.c
index 845e91f179c6088f82c06f431ae44de0e947b9de..16e70ce1912ac2140dcbd01f3d2e63e00e031c69 100644 (file)
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -437,7 +437,7 @@ static void __activate_page(struct page *page, struct lruvec *lruvec,
                SetPageActive(page);
                lru += LRU_ACTIVE;
                add_page_to_lru_list(page, lruvec, lru);
-               trace_mm_lru_activate(page, page_to_pfn(page));
+               trace_mm_lru_activate(page);
 
                __count_vm_event(PGACTIVATE);
                update_page_reclaim_stat(lruvec, file, 1);
@@ -930,7 +930,7 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
        SetPageLRU(page);
        add_page_to_lru_list(page, lruvec, lru);
        update_page_reclaim_stat(lruvec, file, active);
-       trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
+       trace_mm_lru_insertion(page, lru);
 }
 
 /*