Date: Thu, 17 May 2018 18:54:18 -0700 From: Matthew Macy <mmacy@freebsd.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r333775 - in head/sys: kern net sys tests/epoch Message-ID: <CAPrugNoLDevBWSfnt==8Mm2exmfapgEzFrrv6QzUkYq4N7JAvQ@mail.gmail.com> In-Reply-To: <201805180152.w4I1qpxs013915@repo.freebsd.org> References: <201805180152.w4I1qpxs013915@repo.freebsd.org>
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> - epoch_enter_critical() - can be called inside a different epoch,
> starts a section that will acquire any MTX_DEF mutexes or do
> anything that might sleep.
Should read will _not_ acquire ...
> - epoch_exit_critical() - corresponding exit call
> - epoch_wait_critical() - wait variant that is guaranteed that any
> threads in a section are running.
> - epoch_global_critical - an epoch_wait_critical safe epoch instance
>
> Requested by: markj
> Approved by: sbruno
>
> Modified:
> head/sys/kern/subr_epoch.c
> head/sys/net/if.c
> head/sys/sys/epoch.h
> head/sys/tests/epoch/epoch_test.c
>
> Modified: head/sys/kern/subr_epoch.c
> ==============================================================================
> --- head/sys/kern/subr_epoch.c Thu May 17 23:59:56 2018 (r333774)
> +++ head/sys/kern/subr_epoch.c Fri May 18 01:52:51 2018 (r333775)
> @@ -83,6 +83,12 @@ SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nconte
> static counter_u64_t switch_count;
> SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
> &switch_count, "# of times a thread voluntarily context switched in epoch_wait");
> +static counter_u64_t epoch_call_count;
> +SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
> + &epoch_call_count, "# of times a callback was deferred");
> +static counter_u64_t epoch_call_task_count;
> +SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
> + &epoch_call_task_count, "# of times a callback task was run");
>
> TAILQ_HEAD(threadlist, thread);
>
> @@ -103,9 +109,8 @@ struct epoch_pcpu_state {
> struct epoch {
> struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
> struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM] __aligned(EPOCH_ALIGN);
> - counter_u64_t e_frees;
> - uint64_t e_free_last;
> int e_idx;
> + int e_flags;
> struct epoch_pcpu_state *e_pcpu[0];
> };
>
> @@ -119,7 +124,7 @@ static __read_mostly int domoffsets[MAXMEMDOM];
> static __read_mostly int inited;
> static __read_mostly int epoch_count;
> __read_mostly epoch_t global_epoch;
> -static __read_mostly epoch_t private_epoch;
> +__read_mostly epoch_t global_epoch_critical;
>
> static void epoch_call_task(void *context __unused);
>
> @@ -161,8 +166,8 @@ epoch_init(void *arg __unused)
> taskqgroup_attach_cpu(qgroup_softirq, DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, -1, "epoch call task");
> }
> inited = 1;
> - global_epoch = epoch_alloc();
> - private_epoch = epoch_alloc();
> + global_epoch = epoch_alloc(0);
> + global_epoch_critical = epoch_alloc(EPOCH_CRITICAL);
> }
> SYSINIT(epoch, SI_SUB_TASKQ + 1, SI_ORDER_FIRST, epoch_init, NULL);
>
> @@ -206,7 +211,7 @@ epoch_init_legacy(epoch_t epoch)
> }
>
> epoch_t
> -epoch_alloc(void)
> +epoch_alloc(int flags)
> {
> epoch_t epoch;
>
> @@ -215,12 +220,12 @@ 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);
> if (usedomains)
> epoch_init_numa(epoch);
> else
> epoch_init_legacy(epoch);
> MPASS(epoch_count < MAX_EPOCHS-2);
> + epoch->e_flags = flags;
> epoch->e_idx = epoch_count;
> allepochs[epoch_count++] = epoch;
> return (epoch);
> @@ -240,11 +245,7 @@ epoch_free(epoch_t epoch)
> }
> #endif
> allepochs[epoch->e_idx] = NULL;
> - epoch_wait(private_epoch);
> - /*
> - * Execute any lingering callbacks
> - */
> - counter_u64_free(epoch->e_frees);
> + epoch_wait_critical(global_epoch_critical);
> if (usedomains)
> for (domain = 0; domain < vm_ndomains; domain++)
> free_domain(epoch->e_pcpu_dom[domain], M_EPOCH);
> @@ -289,14 +290,21 @@ epoch_enter_internal(epoch_t epoch, struct thread *td)
> }
>
>
> -static void
> -epoch_enter_private(ck_epoch_section_t *section)
> +void
> +epoch_enter_critical(epoch_t epoch)
> {
> - struct epoch_pcpu_state *eps;
> + ck_epoch_record_t *record;
> + ck_epoch_section_t *section;
> + struct thread *td;
>
> - MPASS(curthread->td_critnest);
> - eps = private_epoch->e_pcpu[curcpu];
> - ck_epoch_begin(&eps->eps_record.er_record, section);
> + section = NULL;
> + td = curthread;
> + critical_enter();
> + if (__predict_true(td->td_epochnest++ == 0))
> + section = (ck_epoch_section_t*)&td->td_epoch_section;
> +
> + record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
> + ck_epoch_begin(record, section);
> }
>
> void
> @@ -321,14 +329,21 @@ epoch_exit_internal(epoch_t epoch, struct thread *td)
> critical_exit();
> }
>
> -static void
> -epoch_exit_private(ck_epoch_section_t *section)
> +void
> +epoch_exit_critical(epoch_t epoch)
> {
> - struct epoch_pcpu_state *eps;
> + ck_epoch_record_t *record;
> + ck_epoch_section_t *section;
> + struct thread *td;
>
> - MPASS(curthread->td_critnest);
> - eps = private_epoch->e_pcpu[curcpu];
> - ck_epoch_end(&eps->eps_record.er_record, section);
> + section = NULL;
> + td = curthread;
> + MPASS(td->td_critnest);
> + if (__predict_true(td->td_epochnest-- == 1))
> + section = (ck_epoch_section_t*)&td->td_epoch_section;
> + record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
> + ck_epoch_end(record, section);
> + critical_exit();
> }
>
> /*
> @@ -517,7 +532,24 @@ epoch_wait(epoch_t epoch)
> ("%d residual locks held", td->td_locks - locks));
> }
>
> +static void
> +epoch_block_handler_critical(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused,
> + void *arg __unused)
> +{
> + cpu_spinwait();
> +}
> +
> void
> +epoch_wait_critical(epoch_t epoch)
> +{
> +
> + MPASS(epoch->e_flags & EPOCH_CRITICAL);
> + critical_enter();
> + ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_critical, NULL);
> + critical_exit();
> +}
> +
> +void
> epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t))
> {
> struct epoch_pcpu_state *eps;
> @@ -530,8 +562,6 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*
> if (__predict_false(epoch == NULL))
> goto boottime;
>
> - counter_u64_add(epoch->e_frees, 1);
> -
> critical_enter();
> *DPCPU_PTR(epoch_cb_count) += 1;
> eps = epoch->e_pcpu[curcpu];
> @@ -542,20 +572,18 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*
> callback(ctx);
> }
>
> -
> static void
> epoch_call_task(void *arg __unused)
> {
> ck_stack_entry_t *cursor, *head, *next;
> ck_epoch_record_t *record;
> - ck_epoch_section_t section;
> epoch_t epoch;
> ck_stack_t cb_stack;
> int i, npending, total;
>
> ck_stack_init(&cb_stack);
> critical_enter();
> - epoch_enter_private(§ion);
> + epoch_enter_critical(global_epoch_critical);
> for (total = i = 0; i < epoch_count; i++) {
> if (__predict_false((epoch = allepochs[i]) == NULL))
> continue;
> @@ -565,9 +593,12 @@ epoch_call_task(void *arg __unused)
> ck_epoch_poll_deferred(record, &cb_stack);
> total += npending - record->n_pending;
> }
> - epoch_exit_private(§ion);
> + epoch_exit_critical(global_epoch_critical);
> *DPCPU_PTR(epoch_cb_count) -= total;
> critical_exit();
> +
> + counter_u64_add(epoch_call_count, total);
> + counter_u64_add(epoch_call_task_count, 1);
>
> head = ck_stack_batch_pop_npsc(&cb_stack);
> for (cursor = head; cursor != NULL; cursor = next) {
>
> Modified: head/sys/net/if.c
> ==============================================================================
> --- head/sys/net/if.c Thu May 17 23:59:56 2018 (r333774)
> +++ head/sys/net/if.c Fri May 18 01:52:51 2018 (r333775)
> @@ -903,7 +903,7 @@ if_attachdomain(void *dummy)
> {
> struct ifnet *ifp;
>
> - net_epoch = epoch_alloc();
> + net_epoch = epoch_alloc(0);
> TAILQ_FOREACH(ifp, &V_ifnet, if_link)
> if_attachdomain1(ifp);
> }
>
> Modified: head/sys/sys/epoch.h
> ==============================================================================
> --- head/sys/sys/epoch.h Thu May 17 23:59:56 2018 (r333774)
> +++ head/sys/sys/epoch.h Fri May 18 01:52:51 2018 (r333775)
> @@ -35,7 +35,10 @@
> struct epoch;
> typedef struct epoch *epoch_t;
>
> +#define EPOCH_CRITICAL 0x1
> +
> extern epoch_t global_epoch;
> +extern epoch_t global_epoch_critical;
> DPCPU_DECLARE(int, epoch_cb_count);
> DPCPU_DECLARE(struct grouptask, epoch_cb_task);
>
> @@ -45,11 +48,14 @@ struct epoch_context {
>
> typedef struct epoch_context *epoch_context_t;
>
> -epoch_t epoch_alloc(void);
> +epoch_t epoch_alloc(int flags);
> void epoch_free(epoch_t epoch);
> +void epoch_enter_critical(epoch_t epoch);
> void epoch_enter_internal(epoch_t epoch, struct thread *td);
> +void epoch_exit_critical(epoch_t epoch);
> void epoch_exit_internal(epoch_t epoch, struct thread *td);
> void epoch_wait(epoch_t epoch);
> +void epoch_wait_critical(epoch_t epoch);
> void epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t));
> int in_epoch(void);
>
>
> Modified: head/sys/tests/epoch/epoch_test.c
> ==============================================================================
> --- head/sys/tests/epoch/epoch_test.c Thu May 17 23:59:56 2018 (r333774)
> +++ head/sys/tests/epoch/epoch_test.c Fri May 18 01:52:51 2018 (r333775)
> @@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
>
> #include <sys/param.h>
> #include <sys/types.h>
> +#include <sys/proc.h>
> #include <sys/counter.h>
> #include <sys/epoch.h>
> #include <sys/gtaskqueue.h>
> @@ -138,7 +139,7 @@ test_modinit(void)
> int i, error, pri_range, pri_off;
>
> pri_range = PRI_MIN_TIMESHARE - PRI_MIN_REALTIME;
> - test_epoch = epoch_alloc();
> + test_epoch = epoch_alloc(0);
> for (i = 0; i < mp_ncpus*2; i++) {
> etilist[i].threadid = i;
> error = kthread_add(testloop, &etilist[i], NULL, &testthreads[i],
>
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