From e10f34d6aa1afc820dd7777294071fb63ed67d24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Mon, 1 Oct 2018 19:42:18 +0300
Subject: [PATCH] Remove size restrictions from network reads

The reads now read as much of the data as is available to reduce the
number of distinct malloc calls that need to be made. The SSL_read also
now allocates the buffer before reading into it so that the amount of
copying is reduced.

Also removed some of the not quite helpful debug messages.
---
 include/maxscale/limits.h | 10 ----------
 server/core/dcb.cc        | 21 ++++-----------------
 2 files changed, 4 insertions(+), 27 deletions(-)

diff --git a/include/maxscale/limits.h b/include/maxscale/limits.h
index 994ee5dac..89eff4c3a 100644
--- a/include/maxscale/limits.h
+++ b/include/maxscale/limits.h
@@ -37,16 +37,6 @@ MXS_BEGIN_DECLS
  */
 #define MXS_SO_SNDBUF_SIZE (128 * 1024)
 
-/**
- * MXS_MAX_NW_READ_BUFFER_SIZE
- *
- * The maximum amount of data read in one gofrom a client DCB.
- *
- * TODO: Consider removing altogether so that we always read
- *       whatever is available in the socket.
- */
-#define MXS_MAX_NW_READ_BUFFER_SIZE (32 * 1024)
-
 /**
  * MXS_MAX_THREADS
  *
diff --git a/server/core/dcb.cc b/server/core/dcb.cc
index 6bf44ac8e..ec22f807c 100644
--- a/server/core/dcb.cc
+++ b/server/core/dcb.cc
@@ -692,12 +692,7 @@ static int dcb_read_no_bytes_available(DCB* dcb, int nreadtotal)
 static GWBUF* dcb_basic_read(DCB* dcb, int bytesavailable, int maxbytes, int nreadtotal, int* nsingleread)
 {
     GWBUF* buffer;
-
-    int bufsize = MXS_MIN(bytesavailable, MXS_MAX_NW_READ_BUFFER_SIZE);
-    if (maxbytes)
-    {
-        bufsize = MXS_MIN(bufsize, maxbytes - nreadtotal);
-    }
+    int bufsize = maxbytes == 0 ? bytesavailable : MXS_MIN(bytesavailable, maxbytes - nreadtotal);
 
     if ((buffer = gwbuf_alloc(bufsize)) == NULL)
     {
@@ -787,27 +782,22 @@ static int dcb_read_SSL(DCB* dcb, GWBUF** head)
  */
 static GWBUF* dcb_basic_read_SSL(DCB* dcb, int* nsingleread)
 {
-    unsigned char temp_buffer[MXS_MAX_NW_READ_BUFFER_SIZE];
+    unsigned char temp_buffer[MXS_SO_RCVBUF_SIZE];
     GWBUF* buffer = NULL;
 
-    *nsingleread = SSL_read(dcb->ssl, (void*)temp_buffer, MXS_MAX_NW_READ_BUFFER_SIZE);
+    *nsingleread = SSL_read(dcb->ssl, temp_buffer, MXS_SO_RCVBUF_SIZE);
+
     dcb->stats.n_reads++;
 
     switch (SSL_get_error(dcb->ssl, *nsingleread))
     {
     case SSL_ERROR_NONE:
         /* Successful read */
-        MXS_DEBUG("Read %d bytes from dcb %p in state %s fd %d.",
-                  *nsingleread,
-                  dcb,
-                  STRDCBSTATE(dcb->state),
-                  dcb->fd);
         if (*nsingleread && (buffer = gwbuf_alloc_and_load(*nsingleread, (void*)temp_buffer)) == NULL)
         {
             *nsingleread = -1;
             return NULL;
         }
-
         /* If we were in a retry situation, need to clear flag and attempt write */
         if (dcb->ssl_read_want_write || dcb->ssl_read_want_read)
         {
@@ -819,14 +809,12 @@ static GWBUF* dcb_basic_read_SSL(DCB* dcb, int* nsingleread)
 
     case SSL_ERROR_ZERO_RETURN:
         /* react to the SSL connection being closed */
-        MXS_DEBUG("SSL connection appears to have hung up");
         poll_fake_hangup_event(dcb);
         *nsingleread = 0;
         break;
 
     case SSL_ERROR_WANT_READ:
         /* Prevent SSL I/O on connection until retried, return to poll loop */
-        MXS_DEBUG("SSL connection want read");
         dcb->ssl_read_want_write = false;
         dcb->ssl_read_want_read = true;
         *nsingleread = 0;
@@ -834,7 +822,6 @@ static GWBUF* dcb_basic_read_SSL(DCB* dcb, int* nsingleread)
 
     case SSL_ERROR_WANT_WRITE:
         /* Prevent SSL I/O on connection until retried, return to poll loop */
-        MXS_DEBUG("SSL connection want write");
         dcb->ssl_read_want_write = true;
         dcb->ssl_read_want_read = false;
         *nsingleread = 0;