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https://github.com/fluencelabs/redis
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Avoid installing the client write handler when possible.
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d1b6a17d1e
commit
1c7d87df0c
@ -166,16 +166,18 @@ int prepareClientToWrite(client *c) {
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/* Only install the handler if not already installed and, in case of
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* slaves, if the client can actually receive writes. */
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if (c->bufpos == 0 && listLength(c->reply) == 0 &&
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!(c->flags & CLIENT_PENDING_WRITE) &&
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(c->replstate == REPL_STATE_NONE ||
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(c->replstate == SLAVE_STATE_ONLINE && !c->repl_put_online_on_ack)))
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{
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/* Try to install the write handler. */
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if (aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
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sendReplyToClient, c) == AE_ERR)
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{
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freeClientAsync(c);
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return C_ERR;
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}
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/* Here instead of installing the write handler, we just flag the
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* client and put it into a list of clients that have something
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* to write to the socket. This way before re-entering the event
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* loop, we can try to directly write to the client sockets avoiding
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* a system call. We'll only really install the write handler if
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* we'll not be able to write the whole reply at once. */
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c->flags |= CLIENT_PENDING_WRITE;
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listAddNodeTail(server.clients_pending_write,c);
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}
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/* Authorize the caller to queue in the output buffer of this client. */
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@ -739,6 +741,12 @@ void freeClient(client *c) {
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listDelNode(server.clients,ln);
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}
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/* Remove from the list of pending writes if needed. */
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if (c->flags & CLIENT_PENDING_WRITE) {
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ln = listSearchKey(server.clients_pending_write,c);
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listDelNode(server.clients_pending_write,ln);
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}
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/* When client was just unblocked because of a blocking operation,
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* remove it from the list of unblocked clients. */
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if (c->flags & CLIENT_UNBLOCKED) {
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@ -1857,6 +1857,12 @@ void replicationCacheMaster(client *c) {
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serverAssert(ln != NULL);
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listDelNode(server.clients,ln);
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/* Remove from the list of clients with pending writes as well. */
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if (c->flags & CLIENT_PENDING_WRITE) {
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ln = listSearchKey(server.clients_pending_write,c);
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if (ln) listDelNode(server.clients_pending_write,ln);
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}
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/* Save the master. Server.master will be set to null later by
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* replicationHandleMasterDisconnection(). */
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server.cached_master = server.master;
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32
src/server.c
32
src/server.c
@ -1274,6 +1274,34 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
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return 1000/server.hz;
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}
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/* This function is called just before entering the event loop, in the hope
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* we can just write the replies to the client output buffer without any
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* need to use a syscall in order to install the writable event handler,
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* get it called, and so forth. */
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void handleClientsWithPendingWrites(void) {
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listIter li;
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listNode *ln;
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listRewind(server.clients_pending_write,&li);
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while((ln = listNext(&li))) {
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client *c = listNodeValue(ln);
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c->flags &= ~CLIENT_PENDING_WRITE;
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listDelNode(server.clients_pending_write,ln);
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/* Try to write buffers to the client socket. */
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sendReplyToClient(server.el,c->fd,c,0);
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/* If there is nothing left, do nothing. Otherwise install
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* the write handler. */
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if ((c->bufpos || listLength(c->reply)) &&
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aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
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sendReplyToClient, c) == AE_ERR)
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{
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freeClientAsync(c);
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}
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}
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}
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/* This function gets called every time Redis is entering the
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* main loop of the event driven library, that is, before to sleep
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* for ready file descriptors. */
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@ -1317,6 +1345,9 @@ void beforeSleep(struct aeEventLoop *eventLoop) {
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/* Write the AOF buffer on disk */
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flushAppendOnlyFile(0);
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/* Handle writes with pending output buffers. */
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handleClientsWithPendingWrites();
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}
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/* =========================== Server initialization ======================== */
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@ -1781,6 +1812,7 @@ void initServer(void) {
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server.clients_to_close = listCreate();
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server.slaves = listCreate();
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server.monitors = listCreate();
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server.clients_pending_write = listCreate();
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server.slaveseldb = -1; /* Force to emit the first SELECT command. */
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server.unblocked_clients = listCreate();
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server.ready_keys = listCreate();
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@ -260,6 +260,8 @@ typedef long long mstime_t; /* millisecond time type. */
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#define CLIENT_READONLY (1<<17) /* Cluster client is in read-only state. */
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#define CLIENT_PUBSUB (1<<18) /* Client is in Pub/Sub mode. */
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#define CLIENT_PREVENT_PROP (1<<19) /* Don't propagate to AOF / Slaves. */
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#define CLIENT_PENDING_WRITE (1<<20) /* Client has output to send but a write
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handler is yet not installed. */
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/* Client block type (btype field in client structure)
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* if CLIENT_BLOCKED flag is set. */
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@ -714,6 +716,7 @@ struct redisServer {
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int cfd_count; /* Used slots in cfd[] */
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list *clients; /* List of active clients */
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list *clients_to_close; /* Clients to close asynchronously */
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list *clients_pending_write; /* There is to write or install handler. */
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list *slaves, *monitors; /* List of slaves and MONITORs */
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client *current_client; /* Current client, only used on crash report */
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int clients_paused; /* True if clients are currently paused */
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