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Experimental optimization. Suppose that if sock_recvmsg() returned less data than requested, then next time it will return -EAGAIN, so there's no point to call it again.

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@1236 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Vladislav Bolkhovitin
2009-10-22 12:06:07 +00:00
parent a8414808ab
commit 9c10f10b00
1 changed files with 57 additions and 54 deletions
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111
iscsi-scst/kernel/nthread.c
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@@ -647,68 +647,71 @@ static struct iscsi_cmnd *iscsi_get_send_cmnd(struct iscsi_conn *conn)
static int do_recv(struct iscsi_conn *conn)
{
int res;
mm_segment_t oldfs;
struct msghdr msg;
int first_len;
EXTRACHECKS_BUG_ON(conn->read_cmnd == NULL);
do {
mm_segment_t oldfs;
struct msghdr msg;
int first_len;
if (unlikely(conn->closing)) {
res = -EIO;
goto out;
}
if (unlikely(conn->closing)) {
res = -EIO;
goto out;
/*
* We suppose that if sock_recvmsg() returned less data than requested,
* then next time it will return -EAGAIN, so there's no point to call
* it again.
*/
restart:
memset(&msg, 0, sizeof(msg));
msg.msg_iov = conn->read_msg.msg_iov;
msg.msg_iovlen = conn->read_msg.msg_iovlen;
first_len = msg.msg_iov->iov_len;
oldfs = get_fs();
set_fs(get_ds());
res = sock_recvmsg(conn->sock, &msg, conn->read_size,
MSG_DONTWAIT | MSG_NOSIGNAL);
set_fs(oldfs);
if (res > 0) {
/*
* To save some considerable effort and CPU power we
* suppose that TCP functions adjust
* conn->read_msg.msg_iov and conn->read_msg.msg_iovlen
* on amount of copied data. This BUG_ON is intended
* to catch if it is changed in the future.
*/
sBUG_ON((res >= first_len) &&
(conn->read_msg.msg_iov->iov_len != 0));
conn->read_size -= res;
if (conn->read_size != 0) {
if (res >= first_len) {
int done = 1 + ((res - first_len) >> PAGE_SHIFT);
conn->read_msg.msg_iov += done;
conn->read_msg.msg_iovlen -= done;
}
}
memset(&msg, 0, sizeof(msg));
msg.msg_iov = conn->read_msg.msg_iov;
msg.msg_iovlen = conn->read_msg.msg_iovlen;
first_len = msg.msg_iov->iov_len;
oldfs = get_fs();
set_fs(get_ds());
res = sock_recvmsg(conn->sock, &msg, conn->read_size,
MSG_DONTWAIT | MSG_NOSIGNAL);
set_fs(oldfs);
if (res > 0) {
/*
* To save some considerable effort and CPU power we
* suppose that TCP functions adjust
* conn->read_msg.msg_iov and conn->read_msg.msg_iovlen
* on amount of copied data. This BUG_ON is intended
* to catch if it is changed in the future.
*/
sBUG_ON((res >= first_len) &&
(conn->read_msg.msg_iov->iov_len != 0));
conn->read_size -= res;
if (conn->read_size != 0) {
if (res >= first_len) {
int done = 1 + ((res - first_len) >> PAGE_SHIFT);
conn->read_msg.msg_iov += done;
conn->read_msg.msg_iovlen -= done;
}
}
res = conn->read_size;
} else {
switch (res) {
case -EAGAIN:
TRACE_DBG("EAGAIN received for conn %p", conn);
res = conn->read_size;
} else {
switch (res) {
case -EAGAIN:
TRACE_DBG("EAGAIN received for conn %p", conn);
res = conn->read_size;
break;
case -ERESTARTSYS:
TRACE_DBG("ERESTARTSYS received for conn %p", conn);
continue;
default:
PRINT_ERROR("sock_recvmsg() failed: %d", res);
mark_conn_closed(conn);
if (res == 0)
res = -EIO;
break;
}
break;
case -ERESTARTSYS:
TRACE_DBG("ERESTARTSYS received for conn %p", conn);
goto restart;
default:
PRINT_ERROR("sock_recvmsg() failed: %d", res);
mark_conn_closed(conn);
if (res == 0)
res = -EIO;
break;
}
} while (res > 0);
}
out:
TRACE_EXIT_RES(res);