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    Subject[PATCH v9 8/8] mm: add vmstat counters for tracking PCP drains
    Date
    This patch introduces two new vmstat counters for testing purposes:
    pcp_global_drain that counts the number of times a per-cpu pages
    global drain was requested and pcp_global_ipi_saved that counts
    the number of times the number of CPUs with per-cpu pages in any
    zone were less then 1/2 of the number of online CPUs.

    The patch purpose is to show the usefulness of only sending an IPI
    asking to drain per-cpu pages to CPUs that actually have them
    instead of a blind global IPI. It is not inteded to be merged.

    Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    CC: Christoph Lameter <cl@linux.com>
    CC: Chris Metcalf <cmetcalf@tilera.com>
    CC: Frederic Weisbecker <fweisbec@gmail.com>
    CC: linux-mm@kvack.org
    CC: Pekka Enberg <penberg@kernel.org>
    CC: Matt Mackall <mpm@selenic.com>
    CC: Sasha Levin <levinsasha928@gmail.com>
    CC: Rik van Riel <riel@redhat.com>
    CC: Andi Kleen <andi@firstfloor.org>
    CC: Mel Gorman <mel@csn.ul.ie>
    CC: Andrew Morton <akpm@linux-foundation.org>
    CC: Alexander Viro <viro@zeniv.linux.org.uk>
    CC: Avi Kivity <avi@redhat.com>
    CC: Michal Nazarewicz <mina86@mina86.com>
    CC: Kosaki Motohiro <kosaki.motohiro@gmail.com>
    CC: Milton Miller <miltonm@bga.com>
    CC: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---
    include/linux/vm_event_item.h | 1 +
    mm/page_alloc.c | 5 +++++
    mm/vmstat.c | 2 ++
    3 files changed, 8 insertions(+), 0 deletions(-)

    diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
    index 03b90cd..3657f6f 100644
    --- a/include/linux/vm_event_item.h
    +++ b/include/linux/vm_event_item.h
    @@ -58,6 +58,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
    THP_COLLAPSE_ALLOC_FAILED,
    THP_SPLIT,
    #endif
    + PCP_GLOBAL_DRAIN, PCP_GLOBAL_IPI_SAVED,
    NR_VM_EVENT_ITEMS
    };

    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index 3a2fc84..cdcaf50 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -1202,6 +1202,11 @@ void drain_all_pages(void)
    cpumask_clear_cpu(cpu, &cpus_with_pcps);
    }
    on_each_cpu_mask(&cpus_with_pcps, drain_local_pages, NULL, 1);
    +
    + count_vm_event(PCP_GLOBAL_DRAIN);
    + if (cpumask_weight(&cpus_with_pcps) <
    + (cpumask_weight(cpu_online_mask) / 2))
    + count_vm_event(PCP_GLOBAL_IPI_SAVED);
    }

    #ifdef CONFIG_HIBERNATION
    diff --git a/mm/vmstat.c b/mm/vmstat.c
    index f600557..3ee5f99 100644
    --- a/mm/vmstat.c
    +++ b/mm/vmstat.c
    @@ -786,6 +786,8 @@ const char * const vmstat_text[] = {
    "thp_collapse_alloc_failed",
    "thp_split",
    #endif
    + "pcp_global_drain",
    + "pcp_global_ipi_saved"

    #endif /* CONFIG_VM_EVENTS_COUNTERS */
    };
    --
    1.7.0.4


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