The patch titled
TCP speedup
has been added to the -mm tree. Its filename is
tcp-speedup.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: TCP speedup
From: Wenji Wu <wenji@xxxxxxxx>
For Linux TCP, when the network applcaiton make system call to move data from
socket's receive buffer to user space by calling tcp_recvmsg(). The socket
will be locked. During this period, all the incoming packet for the TCP
socket will go to the backlog queue without being TCP processed
Since Linux 2.6 can be inerrupted mid-task, if the network application
expires, and moved to the expired array with the socket locked, all the
packets within the backlog queue will not be TCP processed till the network
applicaton resume its execution. If the system is heavily loaded, TCP can
easily RTO in the Sender Side.
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/sched.h | 2 ++
kernel/fork.c | 3 +++
kernel/sched.c | 24 ++++++++++++++++++------
net/ipv4/tcp.c | 9 +++++++++
4 files changed, 32 insertions(+), 6 deletions(-)
diff -puN net/ipv4/tcp.c~tcp-speedup net/ipv4/tcp.c
--- a/net/ipv4/tcp.c~tcp-speedup
+++ a/net/ipv4/tcp.c
@@ -1109,6 +1109,8 @@ int tcp_recvmsg(struct kiocb *iocb, stru
struct task_struct *user_recv = NULL;
int copied_early = 0;
+ current->backlog_flag = 1;
+
lock_sock(sk);
TCP_CHECK_TIMER(sk);
@@ -1468,6 +1470,13 @@ skip_copy:
TCP_CHECK_TIMER(sk);
release_sock(sk);
+
+ current->backlog_flag = 0;
+ if (current->extrarun_flag == 1){
+ current->extrarun_flag = 0;
+ yield();
+ }
+
return copied;
out:
diff -puN include/linux/sched.h~tcp-speedup include/linux/sched.h
--- a/include/linux/sched.h~tcp-speedup
+++ a/include/linux/sched.h
@@ -1023,6 +1023,8 @@ struct task_struct {
#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info *delays;
#endif
+ int backlog_flag; /* packets wait in tcp backlog queue flag */
+ int extrarun_flag; /* extra run flag for TCP performance */
};
static inline pid_t process_group(struct task_struct *tsk)
diff -puN kernel/sched.c~tcp-speedup kernel/sched.c
--- a/kernel/sched.c~tcp-speedup
+++ a/kernel/sched.c
@@ -3099,12 +3099,24 @@ void scheduler_tick(void)
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
- if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
- enqueue_task(p, rq->expired);
- if (p->static_prio < rq->best_expired_prio)
- rq->best_expired_prio = p->static_prio;
- } else
- enqueue_task(p, rq->active);
+ if (p->backlog_flag == 0) {
+ if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
+ enqueue_task(p, rq->expired);
+ if (p->static_prio < rq->best_expired_prio)
+ rq->best_expired_prio = p->static_prio;
+ } else
+ enqueue_task(p, rq->active);
+ } else {
+ if (expired_starving(rq)) {
+ enqueue_task(p,rq->expired);
+ if (p->static_prio < rq->best_expired_prio)
+ rq->best_expired_prio = p->static_prio;
+ } else {
+ if (!TASK_INTERACTIVE(p))
+ p->extrarun_flag = 1;
+ enqueue_task(p,rq->active);
+ }
+ }
} else {
/*
* Prevent a too long timeslice allowing a task to monopolize
diff -puN kernel/fork.c~tcp-speedup kernel/fork.c
--- a/kernel/fork.c~tcp-speedup
+++ a/kernel/fork.c
@@ -1032,6 +1032,9 @@ static struct task_struct *copy_process(
clear_tsk_thread_flag(p, TIF_SIGPENDING);
init_sigpending(&p->pending);
+ p->backlog_flag = 0;
+ p->extrarun_flag = 0;
+
p->utime = cputime_zero;
p->stime = cputime_zero;
p->sched_time = 0;
_
Patches currently in -mm which might be from wenji@xxxxxxxx are
tcp-speedup.patch
-
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