Commit-ID: 37355bdc5a129899f6b245900a8eb944a092f7fd Gitweb: https://git.kernel.org/tip/37355bdc5a129899f6b245900a8eb944a092f7fd Author: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> AuthorDate: Mon, 1 Oct 2018 11:05:25 +0100 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 2 Oct 2018 11:31:33 +0200 sched/numa: Migrate pages to local nodes quicker early in the lifetime of a task Automatic NUMA Balancing uses a multi-stage pass to decide whether a page should migrate to a local node. This filter avoids excessive ping-ponging if a page is shared or used by threads that migrate cross-node frequently. Threads inherit both page tables and the preferred node ID from the parent. This means that threads can trigger hinting faults earlier than a new task which delays scanning for a number of seconds. As it can be load balanced very early in its lifetime there can be an unnecessary delay before it starts migrating thread-local data. This patch migrates private pages faster early in the lifetime of a thread using the sequence counter as an identifier of new tasks. With this patch applied, STREAM performance is the same as 4.17 even though processes are not spread cross-node prematurely. Other workloads showed a mix of minor gains and losses. This is somewhat expected most workloads are not very sensitive to the starting conditions of a process. 4.19.0-rc5 4.19.0-rc5 4.17.0 numab-v1r1 fastmigrate-v1r1 vanilla MB/sec copy 43298.52 ( 0.00%) 47335.46 ( 9.32%) 47219.24 ( 9.06%) MB/sec scale 30115.06 ( 0.00%) 32568.12 ( 8.15%) 32527.56 ( 8.01%) MB/sec add 32825.12 ( 0.00%) 36078.94 ( 9.91%) 35928.02 ( 9.45%) MB/sec triad 32549.52 ( 0.00%) 35935.94 ( 10.40%) 35969.88 ( 10.51%) Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Reviewed-by: Rik van Riel <riel@xxxxxxxxxxx> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Jirka Hladky <jhladky@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Linux-MM <linux-mm@xxxxxxxxx> Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/20181001100525.29789-3-mgorman@xxxxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/fair.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 25c7c7e09cbd..7fc4a371bdd2 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1392,6 +1392,17 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, int last_cpupid, this_cpupid; this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); + last_cpupid = page_cpupid_xchg_last(page, this_cpupid); + + /* + * Allow first faults or private faults to migrate immediately early in + * the lifetime of a task. The magic number 4 is based on waiting for + * two full passes of the "multi-stage node selection" test that is + * executed below. + */ + if ((p->numa_preferred_nid == -1 || p->numa_scan_seq <= 4) && + (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid))) + return true; /* * Multi-stage node selection is used in conjunction with a periodic @@ -1410,7 +1421,6 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, * This quadric squishes small probabilities, making it less likely we * act on an unlikely task<->page relation. */ - last_cpupid = page_cpupid_xchg_last(page, this_cpupid); if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != dst_nid) return false;
