svn commit: r333485 - head/sys/kern

[Matt Macy]

Author: mmacy
Date: Fri May 11 08:16:56 2018
New Revision: 333485
URL: https://svnweb.freebsd.org/changeset/base/333485

Log:
  epoch(9): callback task fixes
  
  - initialize the pcpu STAILQ in the NUMA case
  - don't enqueue the callback task if there isn't sufficient work to be done
  
  Reported by:  pho@
  Approved by:  sbruno@

Modified:
  head/sys/kern/subr_epoch.c

Modified: head/sys/kern/subr_epoch.c
==============================================================================
--- head/sys/kern/subr_epoch.c  Fri May 11 07:04:57 2018        (r333484)
+++ head/sys/kern/subr_epoch.c  Fri May 11 08:16:56 2018        (r333485)
@@ -108,6 +108,8 @@ struct epoch {
        int e_flags;
        /* make sure that immutable data doesn't overlap with the gtask, 
callout, and mutex*/
        struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM] __aligned(EPOCH_ALIGN);
+       counter_u64_t e_frees;
+       uint64_t e_free_last;
        struct epoch_pcpu_state *e_pcpu[0];
 };
 
@@ -172,6 +174,7 @@ epoch_init_numa(epoch_t epoch)
                for (int i = 0; i < domcount[domain]; i++, eps++) {
                        epoch->e_pcpu[cpu_offset + i] = eps;
                        er = &eps->eps_record;
+                       STAILQ_INIT(&eps->eps_cblist);
                        ck_epoch_register(&epoch->e_epoch, &er->er_record, 
NULL);
                        TAILQ_INIT((struct threadlist 
*)(uintptr_t)&er->er_tdlist);
                        er->er_cpuid = cpu_offset + i;
@@ -201,9 +204,15 @@ static void
 epoch_callout(void *arg)
 {
        epoch_t epoch;
+       uint64_t frees;
 
        epoch = arg;
-       GROUPTASK_ENQUEUE(&epoch->e_gtask);
+       frees = counter_u64_fetch(epoch->e_frees);
+       /* pick some better value */
+       if (frees - epoch->e_free_last > 10) {
+               GROUPTASK_ENQUEUE(&epoch->e_gtask);
+               epoch->e_free_last = frees;
+       }
        if ((epoch->e_flags & EPOCH_EXITING) == 0)
                callout_reset(&epoch->e_timer, poll_intvl, epoch_callout, 
epoch);
 }
@@ -218,6 +227,7 @@ epoch_alloc(void)
        epoch = malloc(sizeof(struct epoch) + mp_ncpus*sizeof(void*),
                                   M_EPOCH, M_ZERO|M_WAITOK);
        ck_epoch_init(&epoch->e_epoch);
+       epoch->e_frees = counter_u64_alloc(M_WAITOK);
        mtx_init(&epoch->e_lock, "epoch callout", NULL, MTX_DEF);
        callout_init_mtx(&epoch->e_timer, &epoch->e_lock, 0);
        taskqgroup_config_gtask_init(epoch, &epoch->e_gtask, epoch_call_task, 
"epoch call task");
@@ -252,6 +262,7 @@ epoch_free(epoch_t epoch)
        gtaskqueue_drain(epoch->e_gtask.gt_taskqueue, &epoch->e_gtask.gt_task);
        callout_drain(&epoch->e_timer);
        mtx_destroy(&epoch->e_lock);
+       counter_u64_free(epoch->e_frees);
        taskqgroup_config_gtask_deinit(&epoch->e_gtask);
        if (usedomains)
                for (domain = 0; domain < vm_ndomains; domain++)
@@ -534,6 +545,7 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*
        MPASS(epoch);
        MPASS(callback);
        cb->ec_callback = callback;
+       counter_u64_add(epoch->e_frees, 1);
        critical_enter();
        eps = epoch->e_pcpu[curcpu];
        STAILQ_INSERT_HEAD(&eps->eps_cblist, cb, ec_link);
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