diff options
Diffstat (limited to 'src/backend/storage/aio/aio.c')
| -rw-r--r-- | src/backend/storage/aio/aio.c | 1130 |
1 files changed, 1130 insertions, 0 deletions
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c index 828a94efdc3..4d5439c73fd 100644 --- a/src/backend/storage/aio/aio.c +++ b/src/backend/storage/aio/aio.c @@ -3,6 +3,28 @@ * aio.c * AIO - Core Logic * + * For documentation about how AIO works on a higher level, including a + * schematic example, see README.md. + * + * + * AIO is a complicated subsystem. To keep things navigable, it is split + * across a number of files: + * + * - method_*.c - different ways of executing AIO (e.g. worker process) + * + * - aio_target.c - IO on different kinds of targets + * + * - aio_io.c - method-independent code for specific IO ops (e.g. readv) + * + * - aio_callback.c - callbacks at IO operation lifecycle events + * + * - aio_init.c - per-server and per-backend initialization + * + * - aio.c - all other topics + * + * - read_stream.c - helper for reading buffered relation data + * + * * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * @@ -15,10 +37,28 @@ #include "postgres.h" #include "lib/ilist.h" +#include "miscadmin.h" +#include "port/atomics.h" #include "storage/aio.h" +#include "storage/aio_internal.h" #include "storage/aio_subsys.h" #include "utils/guc.h" #include "utils/guc_hooks.h" +#include "utils/resowner.h" +#include "utils/wait_event_types.h" + +#ifdef USE_INJECTION_POINTS +#include "utils/injection_point.h" +#endif + + +static inline void pgaio_io_update_state(PgAioHandle *ioh, PgAioHandleState new_state); +static void pgaio_io_reclaim(PgAioHandle *ioh); +static void pgaio_io_resowner_register(PgAioHandle *ioh); +static void pgaio_io_wait_for_free(void); +static PgAioHandle *pgaio_io_from_wref(PgAioWaitRef *iow, uint64 *ref_generation); +static const char *pgaio_io_state_get_name(PgAioHandleState s); +static void pgaio_io_wait(PgAioHandle *ioh, uint64 ref_generation); /* Options for io_method. */ @@ -31,17 +71,976 @@ const struct config_enum_entry io_method_options[] = { int io_method = DEFAULT_IO_METHOD; int io_max_concurrency = -1; +/* global control for AIO */ +PgAioCtl *pgaio_ctl; + +/* current backend's per-backend state */ +PgAioBackend *pgaio_my_backend; + + +static const IoMethodOps *const pgaio_method_ops_table[] = { + [IOMETHOD_SYNC] = &pgaio_sync_ops, +}; + +/* callbacks for the configured io_method, set by assign_io_method */ +const IoMethodOps *pgaio_method_ops; /* + * Currently there's no infrastructure to pass arguments to injection points, + * so we instead set this up for the duration of the injection point + * invocation. See pgaio_io_call_inj(). + */ +#ifdef USE_INJECTION_POINTS +static PgAioHandle *pgaio_inj_cur_handle; +#endif + + + +/* -------------------------------------------------------------------------------- + * Public Functions related to PgAioHandle + * -------------------------------------------------------------------------------- + */ + +/* + * Acquire an AioHandle, waiting for IO completion if necessary. + * + * Each backend can only have one AIO handle that has been "handed out" to + * code, but not yet submitted or released. This restriction is necessary to + * ensure that it is possible for code to wait for an unused handle by waiting + * for in-flight IO to complete. There is a limited number of handles in each + * backend, if multiple handles could be handed out without being submitted, + * waiting for all in-flight IO to complete would not guarantee that handles + * free up. + * + * It is cheap to acquire an IO handle, unless all handles are in use. In that + * case this function waits for the oldest IO to complete. If that is not + * desirable, use pgaio_io_acquire_nb(). + * + * If a handle was acquired but then does not turn out to be needed, + * e.g. because pgaio_io_acquire() is called before starting an IO in a + * critical section, the handle needs to be released with pgaio_io_release(). + * + * + * To react to the completion of the IO as soon as it is known to have + * completed, callbacks can be registered with pgaio_io_register_callbacks(). + * + * To actually execute IO using the returned handle, the pgaio_io_prep_*() + * family of functions is used. In many cases the pgaio_io_prep_*() call will + * not be done directly by code that acquired the handle, but by lower level + * code that gets passed the handle. E.g. if code in bufmgr.c wants to perform + * AIO, it typically will pass the handle to smgr.c, which will pass it on to + * md.c, on to fd.c, which then finally calls pgaio_io_prep_*(). This + * forwarding allows the various layers to react to the IO's completion by + * registering callbacks. These callbacks in turn can translate a lower + * layer's result into a result understandable by a higher layer. + * + * During pgaio_io_prep_*() the IO is staged (i.e. prepared for execution but + * not submitted to the kernel). Unless in batchmode + * (c.f. pgaio_enter_batchmode()), the IO will also get submitted for + * execution. Note that, whether in batchmode or not, the IO might even + * complete before the functions return. + * + * After pgaio_io_prep_*() the AioHandle is "consumed" and may not be + * referenced by the IO issuing code. To e.g. wait for IO, references to the + * IO can be established with pgaio_io_get_wref() *before* pgaio_io_prep_*() + * is called. pgaio_wref_wait() can be used to wait for the IO to complete. + * + * + * To know if the IO [partially] succeeded or failed, a PgAioReturn * can be + * passed to pgaio_io_acquire(). Once the issuing backend has called + * pgaio_wref_wait(), the PgAioReturn contains information about whether the + * operation succeeded and details about the first failure, if any. The error + * can be raised / logged with pgaio_result_report(). + * + * The lifetime of the memory pointed to be *ret needs to be at least as long + * as the passed in resowner. If the resowner releases resources before the IO + * completes (typically due to an error), the reference to *ret will be + * cleared. In case of resowner cleanup *ret will not be updated with the + * results of the IO operation. + */ +PgAioHandle * +pgaio_io_acquire(struct ResourceOwnerData *resowner, PgAioReturn *ret) +{ + PgAioHandle *h; + + while (true) + { + h = pgaio_io_acquire_nb(resowner, ret); + + if (h != NULL) + return h; + + /* + * Evidently all handles by this backend are in use. Just wait for + * some to complete. + */ + pgaio_io_wait_for_free(); + } +} + +/* + * Acquire an AioHandle, returning NULL if no handles are free. + * + * See pgaio_io_acquire(). The only difference is that this function will return + * NULL if there are no idle handles, instead of blocking. + */ +PgAioHandle * +pgaio_io_acquire_nb(struct ResourceOwnerData *resowner, PgAioReturn *ret) +{ + if (pgaio_my_backend->num_staged_ios >= PGAIO_SUBMIT_BATCH_SIZE) + { + Assert(pgaio_my_backend->num_staged_ios == PGAIO_SUBMIT_BATCH_SIZE); + pgaio_submit_staged(); + } + + if (pgaio_my_backend->handed_out_io) + elog(ERROR, "API violation: Only one IO can be handed out"); + + if (!dclist_is_empty(&pgaio_my_backend->idle_ios)) + { + dlist_node *ion = dclist_pop_head_node(&pgaio_my_backend->idle_ios); + PgAioHandle *ioh = dclist_container(PgAioHandle, node, ion); + + Assert(ioh->state == PGAIO_HS_IDLE); + Assert(ioh->owner_procno == MyProcNumber); + + pgaio_io_update_state(ioh, PGAIO_HS_HANDED_OUT); + pgaio_my_backend->handed_out_io = ioh; + + if (resowner) + pgaio_io_resowner_register(ioh); + + if (ret) + { + ioh->report_return = ret; + ret->result.status = ARS_UNKNOWN; + } + + return ioh; + } + + return NULL; +} + +/* + * Release IO handle that turned out to not be required. + * + * See pgaio_io_acquire() for more details. + */ +void +pgaio_io_release(PgAioHandle *ioh) +{ + if (ioh == pgaio_my_backend->handed_out_io) + { + Assert(ioh->state == PGAIO_HS_HANDED_OUT); + Assert(ioh->resowner); + + pgaio_my_backend->handed_out_io = NULL; + pgaio_io_reclaim(ioh); + } + else + { + elog(ERROR, "release in unexpected state"); + } +} + +/* * Release IO handle during resource owner cleanup. */ void pgaio_io_release_resowner(dlist_node *ioh_node, bool on_error) { + PgAioHandle *ioh = dlist_container(PgAioHandle, resowner_node, ioh_node); + + Assert(ioh->resowner); + + ResourceOwnerForgetAioHandle(ioh->resowner, &ioh->resowner_node); + ioh->resowner = NULL; + + switch (ioh->state) + { + case PGAIO_HS_IDLE: + elog(ERROR, "unexpected"); + break; + case PGAIO_HS_HANDED_OUT: + Assert(ioh == pgaio_my_backend->handed_out_io || pgaio_my_backend->handed_out_io == NULL); + + if (ioh == pgaio_my_backend->handed_out_io) + { + pgaio_my_backend->handed_out_io = NULL; + if (!on_error) + elog(WARNING, "leaked AIO handle"); + } + + pgaio_io_reclaim(ioh); + break; + case PGAIO_HS_DEFINED: + case PGAIO_HS_STAGED: + if (!on_error) + elog(WARNING, "AIO handle was not submitted"); + pgaio_submit_staged(); + break; + case PGAIO_HS_SUBMITTED: + case PGAIO_HS_COMPLETED_IO: + case PGAIO_HS_COMPLETED_SHARED: + case PGAIO_HS_COMPLETED_LOCAL: + /* this is expected to happen */ + break; + } + + /* + * Need to unregister the reporting of the IO's result, the memory it's + * referencing likely has gone away. + */ + if (ioh->report_return) + ioh->report_return = NULL; +} + +/* + * Add a [set of] flags to the IO. + * + * Note that this combines flags with already set flags, rather than set flags + * to explicitly the passed in parameters. This is to allow multiple callsites + * to set flags. + */ +void +pgaio_io_set_flag(PgAioHandle *ioh, PgAioHandleFlags flag) +{ + Assert(ioh->state == PGAIO_HS_HANDED_OUT); + + ioh->flags |= flag; +} + +/* + * Returns an ID uniquely identifying the IO handle. This is only really + * useful for logging, as handles are reused across multiple IOs. + */ +int +pgaio_io_get_id(PgAioHandle *ioh) +{ + Assert(ioh >= pgaio_ctl->io_handles && + ioh < (pgaio_ctl->io_handles + pgaio_ctl->io_handle_count)); + return ioh - pgaio_ctl->io_handles; +} + +/* + * Return the ProcNumber for the process that can use an IO handle. The + * mapping from IO handles to PGPROCs is static, therefore this even works + * when the corresponding PGPROC is not in use. + */ +ProcNumber +pgaio_io_get_owner(PgAioHandle *ioh) +{ + return ioh->owner_procno; +} + +/* + * Return a wait reference for the IO. Only wait references can be used to + * wait for an IOs completion, as handles themselves can be reused after + * completion. See also the comment above pgaio_io_acquire(). + */ +void +pgaio_io_get_wref(PgAioHandle *ioh, PgAioWaitRef *iow) +{ + Assert(ioh->state == PGAIO_HS_HANDED_OUT || + ioh->state == PGAIO_HS_DEFINED || + ioh->state == PGAIO_HS_STAGED); + Assert(ioh->generation != 0); + + iow->aio_index = ioh - pgaio_ctl->io_handles; + iow->generation_upper = (uint32) (ioh->generation >> 32); + iow->generation_lower = (uint32) ioh->generation; +} + + + +/* -------------------------------------------------------------------------------- + * Internal Functions related to PgAioHandle + * -------------------------------------------------------------------------------- + */ + +static inline void +pgaio_io_update_state(PgAioHandle *ioh, PgAioHandleState new_state) +{ + pgaio_debug_io(DEBUG5, ioh, + "updating state to %s", + pgaio_io_state_get_name(new_state)); + + /* + * Ensure the changes signified by the new state are visible before the + * new state becomes visible. + */ + pg_write_barrier(); + + ioh->state = new_state; +} + +static void +pgaio_io_resowner_register(PgAioHandle *ioh) +{ + Assert(!ioh->resowner); + Assert(CurrentResourceOwner); + + ResourceOwnerRememberAioHandle(CurrentResourceOwner, &ioh->resowner_node); + ioh->resowner = CurrentResourceOwner; +} + +/* + * Stage IO for execution and, if appropriate, submit it immediately. + * + * Should only be called from pgaio_io_prep_*(). + */ +void +pgaio_io_stage(PgAioHandle *ioh, PgAioOp op) +{ + bool needs_synchronous; + + Assert(ioh->state == PGAIO_HS_HANDED_OUT); + Assert(pgaio_my_backend->handed_out_io == ioh); + Assert(pgaio_io_has_target(ioh)); + + ioh->op = op; + ioh->result = 0; + + pgaio_io_update_state(ioh, PGAIO_HS_DEFINED); + + /* allow a new IO to be staged */ + pgaio_my_backend->handed_out_io = NULL; + + pgaio_io_call_stage(ioh); + + pgaio_io_update_state(ioh, PGAIO_HS_STAGED); + + /* + * Synchronous execution has to be executed, well, synchronously, so check + * that first. + */ + needs_synchronous = pgaio_io_needs_synchronous_execution(ioh); + + pgaio_debug_io(DEBUG3, ioh, + "prepared (synchronous: %d, in_batch: %d)", + needs_synchronous, pgaio_my_backend->in_batchmode); + + if (!needs_synchronous) + { + pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh; + Assert(pgaio_my_backend->num_staged_ios <= PGAIO_SUBMIT_BATCH_SIZE); + + /* + * Unless code explicitly opted into batching IOs, submit the IO + * immediately. + */ + if (!pgaio_my_backend->in_batchmode) + pgaio_submit_staged(); + } + else + { + pgaio_io_prepare_submit(ioh); + pgaio_io_perform_synchronously(ioh); + } +} + +bool +pgaio_io_needs_synchronous_execution(PgAioHandle *ioh) +{ + /* + * If the caller said to execute the IO synchronously, do so. + * + * XXX: We could optimize the logic when to execute synchronously by first + * checking if there are other IOs in flight and only synchronously + * executing if not. Unclear whether that'll be sufficiently common to be + * worth worrying about. + */ + if (ioh->flags & PGAIO_HF_SYNCHRONOUS) + return true; + + /* Check if the IO method requires synchronous execution of IO */ + if (pgaio_method_ops->needs_synchronous_execution) + return pgaio_method_ops->needs_synchronous_execution(ioh); + + return false; +} + +/* + * Handle IO being processed by IO method. + * + * Should be called by IO methods / synchronous IO execution, just before the + * IO is performed. + */ +void +pgaio_io_prepare_submit(PgAioHandle *ioh) +{ + pgaio_io_update_state(ioh, PGAIO_HS_SUBMITTED); + + dclist_push_tail(&pgaio_my_backend->in_flight_ios, &ioh->node); +} + +/* + * Handle IO getting completed by a method. + * + * Should be called by IO methods / synchronous IO execution, just after the + * IO has been performed. + * + * Expects to be called in a critical section. We expect IOs to be usable for + * WAL etc, which requires being able to execute completion callbacks in a + * critical section. + */ +void +pgaio_io_process_completion(PgAioHandle *ioh, int result) +{ + Assert(ioh->state == PGAIO_HS_SUBMITTED); + + Assert(CritSectionCount > 0); + + ioh->result = result; + + pgaio_io_update_state(ioh, PGAIO_HS_COMPLETED_IO); + + pgaio_io_call_inj(ioh, "AIO_PROCESS_COMPLETION_BEFORE_SHARED"); + + pgaio_io_call_complete_shared(ioh); + + pgaio_io_update_state(ioh, PGAIO_HS_COMPLETED_SHARED); + + /* condition variable broadcast ensures state is visible before wakeup */ + ConditionVariableBroadcast(&ioh->cv); + + /* contains call to pgaio_io_call_complete_local() */ + if (ioh->owner_procno == MyProcNumber) + pgaio_io_reclaim(ioh); +} + +/* + * Has the IO completed and thus the IO handle been reused? + * + * This is useful when waiting for IO completion at a low level (e.g. in an IO + * method's ->wait_one() callback). + */ +bool +pgaio_io_was_recycled(PgAioHandle *ioh, uint64 ref_generation, PgAioHandleState *state) +{ + *state = ioh->state; + pg_read_barrier(); + + return ioh->generation != ref_generation; +} + +/* + * Wait for IO to complete. External code should never use this, outside of + * the AIO subsystem waits are only allowed via pgaio_wref_wait(). + */ +static void +pgaio_io_wait(PgAioHandle *ioh, uint64 ref_generation) +{ + PgAioHandleState state; + bool am_owner; + + am_owner = ioh->owner_procno == MyProcNumber; + + if (pgaio_io_was_recycled(ioh, ref_generation, &state)) + return; + + if (am_owner) + { + if (state != PGAIO_HS_SUBMITTED + && state != PGAIO_HS_COMPLETED_IO + && state != PGAIO_HS_COMPLETED_SHARED + && state != PGAIO_HS_COMPLETED_LOCAL) + { + elog(PANIC, "waiting for own IO in wrong state: %d", + state); + } + } + + while (true) + { + if (pgaio_io_was_recycled(ioh, ref_generation, &state)) + return; + + switch (state) + { + case PGAIO_HS_IDLE: + case PGAIO_HS_HANDED_OUT: + elog(ERROR, "IO in wrong state: %d", state); + break; + + case PGAIO_HS_SUBMITTED: + + /* + * If we need to wait via the IO method, do so now. Don't + * check via the IO method if the issuing backend is executing + * the IO synchronously. + */ + if (pgaio_method_ops->wait_one && !(ioh->flags & PGAIO_HF_SYNCHRONOUS)) + { + pgaio_method_ops->wait_one(ioh, ref_generation); + continue; + } + /* fallthrough */ + + /* waiting for owner to submit */ + case PGAIO_HS_DEFINED: + case PGAIO_HS_STAGED: + /* waiting for reaper to complete */ + /* fallthrough */ + case PGAIO_HS_COMPLETED_IO: + /* shouldn't be able to hit this otherwise */ + Assert(IsUnderPostmaster); + /* ensure we're going to get woken up */ + ConditionVariablePrepareToSleep(&ioh->cv); + + while (!pgaio_io_was_recycled(ioh, ref_generation, &state)) + { + if (state == PGAIO_HS_COMPLETED_SHARED || + state == PGAIO_HS_COMPLETED_LOCAL) + break; + ConditionVariableSleep(&ioh->cv, WAIT_EVENT_AIO_IO_COMPLETION); + } + + ConditionVariableCancelSleep(); + break; + + case PGAIO_HS_COMPLETED_SHARED: + case PGAIO_HS_COMPLETED_LOCAL: + /* see above */ + if (am_owner) + pgaio_io_reclaim(ioh); + return; + } + } +} + +/* + * Make IO handle ready to be reused after IO has completed or after the + * handle has been released without being used. + */ +static void +pgaio_io_reclaim(PgAioHandle *ioh) +{ + /* This is only ok if it's our IO */ + Assert(ioh->owner_procno == MyProcNumber); + Assert(ioh->state != PGAIO_HS_IDLE); + + /* + * It's a bit ugly, but right now the easiest place to put the execution + * of shared completion callbacks is this function, as we need to execute + * local callbacks just before reclaiming at multiple callsites. + */ + if (ioh->state == PGAIO_HS_COMPLETED_SHARED) + { + pgaio_io_call_complete_local(ioh); + pgaio_io_update_state(ioh, PGAIO_HS_COMPLETED_LOCAL); + } + + pgaio_debug_io(DEBUG4, ioh, + "reclaiming: distilled_result: (status %s, id %u, error_data %d), raw_result: %d", + pgaio_result_status_string(ioh->distilled_result.status), + ioh->distilled_result.id, + ioh->distilled_result.error_data, + ioh->result); + + /* if the IO has been defined, we might need to do more work */ + if (ioh->state != PGAIO_HS_HANDED_OUT) + { + dclist_delete_from(&pgaio_my_backend->in_flight_ios, &ioh->node); + + if (ioh->report_return) + { + ioh->report_return->result = ioh->distilled_result; + ioh->report_return->target_data = ioh->target_data; + } + } + + if (ioh->resowner) + { + ResourceOwnerForgetAioHandle(ioh->resowner, &ioh->resowner_node); + ioh->resowner = NULL; + } + + Assert(!ioh->resowner); + + ioh->op = PGAIO_OP_INVALID; + ioh->target = PGAIO_TID_INVALID; + ioh->flags = 0; + ioh->num_callbacks = 0; + ioh->handle_data_len = 0; + ioh->report_return = NULL; + ioh->result = 0; + ioh->distilled_result.status = ARS_UNKNOWN; + + /* XXX: the barrier is probably superfluous */ + pg_write_barrier(); + ioh->generation++; + + pgaio_io_update_state(ioh, PGAIO_HS_IDLE); + + /* + * We push the IO to the head of the idle IO list, that seems more cache + * efficient in cases where only a few IOs are used. + */ + dclist_push_head(&pgaio_my_backend->idle_ios, &ioh->node); +} + +/* + * Wait for an IO handle to become usable. + * + * This only really is useful for pgaio_io_acquire(). + */ +static void +pgaio_io_wait_for_free(void) +{ + int reclaimed = 0; + + pgaio_debug(DEBUG2, "waiting for self with %d pending", + pgaio_my_backend->num_staged_ios); + + /* + * First check if any of our IOs actually have completed - when using + * worker, that'll often be the case. We could do so as part of the loop + * below, but that'd potentially lead us to wait for some IO submitted + * before. + */ + for (int i = 0; i < io_max_concurrency; i++) + { + PgAioHandle *ioh = &pgaio_ctl->io_handles[pgaio_my_backend->io_handle_off + i]; + + if (ioh->state == PGAIO_HS_COMPLETED_SHARED) + { + pgaio_io_reclaim(ioh); + reclaimed++; + } + } + + if (reclaimed > 0) + return; + + /* + * If we have any unsubmitted IOs, submit them now. We'll start waiting in + * a second, so it's better they're in flight. This also addresses the + * edge-case that all IOs are unsubmitted. + */ + if (pgaio_my_backend->num_staged_ios > 0) + pgaio_submit_staged(); + + if (dclist_count(&pgaio_my_backend->in_flight_ios) == 0) + elog(ERROR, "no free IOs despite no in-flight IOs"); + + /* + * Wait for the oldest in-flight IO to complete. + * + * XXX: Reusing the general IO wait is suboptimal, we don't need to wait + * for that specific IO to complete, we just need *any* IO to complete. + */ + { + PgAioHandle *ioh = dclist_head_element(PgAioHandle, node, + &pgaio_my_backend->in_flight_ios); + + switch (ioh->state) + { + /* should not be in in-flight list */ + case PGAIO_HS_IDLE: + case PGAIO_HS_DEFINED: + case PGAIO_HS_HANDED_OUT: + case PGAIO_HS_STAGED: + case PGAIO_HS_COMPLETED_LOCAL: + elog(ERROR, "shouldn't get here with io:%d in state %d", + pgaio_io_get_id(ioh), ioh->state); + break; + + case PGAIO_HS_COMPLETED_IO: + case PGAIO_HS_SUBMITTED: + pgaio_debug_io(DEBUG2, ioh, + "waiting for free io with %d in flight", + dclist_count(&pgaio_my_backend->in_flight_ios)); + + /* + * In a more general case this would be racy, because the + * generation could increase after we read ioh->state above. + * But we are only looking at IOs by the current backend and + * the IO can only be recycled by this backend. + */ + pgaio_io_wait(ioh, ioh->generation); + break; + + case PGAIO_HS_COMPLETED_SHARED: + /* it's possible that another backend just finished this IO */ + pgaio_io_reclaim(ioh); + break; + } + + if (dclist_count(&pgaio_my_backend->idle_ios) == 0) + elog(PANIC, "no idle IO after waiting for IO to terminate"); + return; + } +} + +/* + * Internal - code outside of AIO should never need this and it'd be hard for + * such code to be safe. + */ +static PgAioHandle * +pgaio_io_from_wref(PgAioWaitRef *iow, uint64 *ref_generation) +{ + PgAioHandle *ioh; + + Assert(iow->aio_index < pgaio_ctl->io_handle_count); + + ioh = &pgaio_ctl->io_handles[iow->aio_index]; + + *ref_generation = ((uint64) iow->generation_upper) << 32 | + iow->generation_lower; + + Assert(*ref_generation != 0); + + return ioh; +} + +static const char * +pgaio_io_state_get_name(PgAioHandleState s) +{ +#define PGAIO_HS_TOSTR_CASE(sym) case PGAIO_HS_##sym: return #sym + switch (s) + { + PGAIO_HS_TOSTR_CASE(IDLE); + PGAIO_HS_TOSTR_CASE(HANDED_OUT); + PGAIO_HS_TOSTR_CASE(DEFINED); + PGAIO_HS_TOSTR_CASE(STAGED); + PGAIO_HS_TOSTR_CASE(SUBMITTED); + PGAIO_HS_TOSTR_CASE(COMPLETED_IO); + PGAIO_HS_TOSTR_CASE(COMPLETED_SHARED); + PGAIO_HS_TOSTR_CASE(COMPLETED_LOCAL); + } +#undef PGAIO_HS_TOSTR_CASE + + return NULL; /* silence compiler */ +} + +const char * +pgaio_io_get_state_name(PgAioHandle *ioh) +{ + return pgaio_io_state_get_name(ioh->state); +} + +const char * +pgaio_result_status_string(PgAioResultStatus rs) +{ + switch (rs) + { + case ARS_UNKNOWN: + return "UNKNOWN"; + case ARS_OK: + return "OK"; + case ARS_PARTIAL: + return "PARTIAL"; + case ARS_ERROR: + return "ERROR"; + } + + return NULL; /* silence compiler */ +} + + + +/* -------------------------------------------------------------------------------- + * Functions primarily related to IO Wait References + * -------------------------------------------------------------------------------- + */ + +/* + * Mark a wait reference as invalid + */ +void +pgaio_wref_clear(PgAioWaitRef *iow) +{ + iow->aio_index = PG_UINT32_MAX; +} + +/* Is the wait reference valid? */ +bool +pgaio_wref_valid(PgAioWaitRef *iow) +{ + return iow->aio_index != PG_UINT32_MAX; +} + +/* + * Similar to pgaio_io_get_id(), just for wait references. + */ +int +pgaio_wref_get_id(PgAioWaitRef *iow) +{ + Assert(pgaio_wref_valid(iow)); + return iow->aio_index; +} + +/* + * Wait for the IO to have completed. Can be called in any process, not just + * in the issuing backend. + */ +void +pgaio_wref_wait(PgAioWaitRef *iow) +{ + uint64 ref_generation; + PgAioHandle *ioh; + + ioh = pgaio_io_from_wref(iow, &ref_generation); + + pgaio_io_wait(ioh, ref_generation); +} + +/* + * Check if the referenced IO completed, without blocking. + */ +bool +pgaio_wref_check_done(PgAioWaitRef *iow) +{ + uint64 ref_generation; + PgAioHandleState state; + bool am_owner; + PgAioHandle *ioh; + + ioh = pgaio_io_from_wref(iow, &ref_generation); + + if (pgaio_io_was_recycled(ioh, ref_generation, &state)) + return true; + + if (state == PGAIO_HS_IDLE) + return true; + + am_owner = ioh->owner_procno == MyProcNumber; + + if (state == PGAIO_HS_COMPLETED_SHARED || + state == PGAIO_HS_COMPLETED_LOCAL) + { + if (am_owner) + pgaio_io_reclaim(ioh); + return true; + } + + /* + * XXX: It likely would be worth checking in with the io method, to give + * the IO method a chance to check if there are completion events queued. + */ + + return false; +} + + + +/* -------------------------------------------------------------------------------- + * Actions on multiple IOs. + * -------------------------------------------------------------------------------- + */ + +/* + * Submit IOs in batches going forward. + * + * Submitting multiple IOs at once can be substantially faster than doing so + * one-by-one. At the same time, submitting multiple IOs at once requires more + * care to avoid deadlocks. + * + * Consider backend A staging an IO for buffer 1 and then trying to start IO + * on buffer 2, while backend B does the inverse. If A submitted the IO before + * moving on to buffer 2, this works just fine, B will wait for the IO to + * complete. But if batching were used, each backend will wait for IO that has + * not yet been submitted to complete, i.e. forever. + * + * End batch submission mode with pgaio_exit_batchmode(). (Throwing errors is + * allowed; error recovery will end the batch.) + * + * To avoid deadlocks, code needs to ensure that it will not wait for another + * backend while there is unsubmitted IO. E.g. by using conditional lock + * acquisition when acquiring buffer locks. To check if there currently are + * staged IOs, call pgaio_have_staged() and to submit all staged IOs call + * pgaio_submit_staged(). + * + * It is not allowed to enter batchmode while already in batchmode, it's + * unlikely to ever be needed, as code needs to be explicitly aware of being + * called in batchmode, to avoid the deadlock risks explained above. + * + * Note that IOs may get submitted before pgaio_exit_batchmode() is called, + * e.g. because too many IOs have been staged or because pgaio_submit_staged() + * was called. + */ +void +pgaio_enter_batchmode(void) +{ + if (pgaio_my_backend->in_batchmode) + elog(ERROR, "starting batch while batch already in progress"); + pgaio_my_backend->in_batchmode = true; } /* + * Stop submitting IOs in batches. + */ +void +pgaio_exit_batchmode(void) +{ + Assert(pgaio_my_backend->in_batchmode); + + pgaio_submit_staged(); + pgaio_my_backend->in_batchmode = false; +} + +/* + * Are there staged but unsubmitted IOs? + * + * See comment above pgaio_enter_batchmode() for why code may need to check if + * there is IO in that state. + */ +bool +pgaio_have_staged(void) +{ + Assert(pgaio_my_backend->in_batchmode || + pgaio_my_backend->num_staged_ios == 0); + return pgaio_my_backend->num_staged_ios > 0; +} + +/* + * Submit all staged but not yet submitted IOs. + * + * Unless in batch mode, this never needs to be called, as IOs get submitted + * as soon as possible. While in batchmode pgaio_submit_staged() can be called + * before waiting on another backend, to avoid the risk of deadlocks. See + * pgaio_enter_batchmode(). + */ +void +pgaio_submit_staged(void) +{ + int total_submitted = 0; + int did_submit; + + if (pgaio_my_backend->num_staged_ios == 0) + return; + + + START_CRIT_SECTION(); + + did_submit = pgaio_method_ops->submit(pgaio_my_backend->num_staged_ios, + pgaio_my_backend->staged_ios); + + END_CRIT_SECTION(); + + total_submitted += did_submit; + + Assert(total_submitted == did_submit); + + pgaio_my_backend->num_staged_ios = 0; + + pgaio_debug(DEBUG4, + "aio: submitted %d IOs", + total_submitted); +} + + + +/* -------------------------------------------------------------------------------- + * Other + * -------------------------------------------------------------------------------- + */ + + +/* * Perform AIO related cleanup after an error. * * This should be called early in the error recovery paths, as later steps may @@ -50,6 +1049,22 @@ pgaio_io_release_resowner(dlist_node *ioh_node, bool on_error) void pgaio_error_cleanup(void) { + /* + * It is possible that code errored out after pgaio_enter_batchmode() but + * before pgaio_exit_batchmode() was called. In that case we need to + * submit the IO now. + */ + if (pgaio_my_backend->in_batchmode) + { + pgaio_my_backend->in_batchmode = false; + + pgaio_submit_staged(); + } + + /* + * As we aren't in batchmode, there shouldn't be any unsubmitted IOs. + */ + Assert(pgaio_my_backend->num_staged_ios == 0); } /* @@ -62,11 +1077,86 @@ pgaio_error_cleanup(void) void AtEOXact_Aio(bool is_commit) { + /* + * We should never be in batch mode at transactional boundaries. In case + * an error was thrown while in batch mode, pgaio_error_cleanup() should + * have exited batchmode. + * + * In case we are in batchmode somehow, make sure to submit all staged + * IOs, other backends may need them to complete to continue. + */ + if (pgaio_my_backend->in_batchmode) + { + pgaio_error_cleanup(); + elog(WARNING, "open AIO batch at end of (sub-)transaction"); + } + + /* + * As we aren't in batchmode, there shouldn't be any unsubmitted IOs. + */ + Assert(pgaio_my_backend->num_staged_ios == 0); +} + +/* + * Need to submit staged but not yet submitted IOs using the fd, otherwise + * the IO would end up targeting something bogus. + */ +void +pgaio_closing_fd(int fd) +{ + /* + * Might be called before AIO is initialized or in a subprocess that + * doesn't use AIO. + */ + if (!pgaio_my_backend) + return; + + /* + * For now just submit all staged IOs - we could be more selective, but + * it's probably not worth it. + */ + pgaio_submit_staged(); +} + +/* + * Registered as before_shmem_exit() callback in pgaio_init_backend() + */ +void +pgaio_shutdown(int code, Datum arg) +{ + Assert(pgaio_my_backend); + Assert(!pgaio_my_backend->handed_out_io); + + /* first clean up resources as we would at a transaction boundary */ + AtEOXact_Aio(code == 0); + + /* + * Before exiting, make sure that all IOs are finished. That has two main + * purposes: + * + * - Some kernel-level AIO mechanisms don't deal well with the issuer of + * an AIO exiting before IO completed + * + * - It'd be confusing to see partially finished IOs in stats views etc + */ + while (!dclist_is_empty(&pgaio_my_backend->in_flight_ios)) + { + PgAioHandle *ioh = dclist_head_element(PgAioHandle, node, &pgaio_my_backend->in_flight_ios); + + /* see comment in pgaio_io_wait_for_free() about raciness */ + pgaio_io_wait(ioh, ioh->generation); + } + + pgaio_my_backend = NULL; } void assign_io_method(int newval, void *extra) { + Assert(pgaio_method_ops_table[newval] != NULL); + Assert(newval < lengthof(io_method_options)); + + pgaio_method_ops = pgaio_method_ops_table[newval]; } bool @@ -88,3 +1178,43 @@ check_io_max_concurrency(int *newval, void **extra, GucSource source) return true; } + + + +/* -------------------------------------------------------------------------------- + * Injection point support + * -------------------------------------------------------------------------------- + */ + +#ifdef USE_INJECTION_POINTS + +/* + * Call injection point with support for pgaio_inj_io_get(). + */ +void +pgaio_io_call_inj(PgAioHandle *ioh, const char *injection_point) +{ + pgaio_inj_cur_handle = ioh; + + PG_TRY(); + { + InjectionPointCached(injection_point); + } + PG_FINALLY(); + { + pgaio_inj_cur_handle = NULL; + } + PG_END_TRY(); +} + +/* + * Return IO associated with injection point invocation. This is only needed + * as injection points currently don't support arguments. + */ +PgAioHandle * +pgaio_inj_io_get(void) +{ + return pgaio_inj_cur_handle; +} + +#endif |