lkml.org 
[lkml]   [2012]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subject[RFC] Introduce to batch variants of accept() and epoll_ctl() syscall
Hi,

We encounter a performance problem in a large scale computer
cluster, which needs to handle a lot of incoming concurrent TCP
connection requests.

The top shows the kernel is most cpu hog, the testing is simple,
just a accept() -> epoll_ctl(ADD) loop, the ratio of cpu util sys% to
si% is about 2:5.

I also asked some experienced webserver/proxy developers in my team
for suggestions, it seem that behavior of many userland programs already
called accept() multiple times after it is waked up by
epoll_wait(). And the common action is adding the fd that accept()
return into epoll interface by epoll_ctl() syscall then.

Therefore, I think that we'd better to introduce to batch variants of
accept() and epoll_ctl() syscall, just like sendmmsg() or recvmmsg().

For accept(), we may need a new syscall, it may like this,

struct accept_result {
int fd;
struct sockaddr addr;
socklen_t addr_len;
};

int maccept4(int fd, int flags, int nr_accept_result, struct
accept_result *results);

For epoll_ctl(), there are two means to extend it, I prefer to extend
current interface instead of introduce to new syscall. We may introduce
to a new flag EPOLL_CTL_BATCH. If userland call epoll_ctl() with this
flag set, the meaning of last two arguments of epoll_ctl() change, .e.g:

struct batch_epoll_event batch_event[] = {
{
.fd = a_newsock_fd;
.epoll_event = { ... };
},
...
};

ret = epoll_ctl(fd, EPOLL_CTL_ADD|EPOLL_CTL_BATCH, nr_batch_events,
batch_events);

Thanks.

Yu


\
 
 \ /
  Last update: 2012-06-15 07:02    [W:0.131 / U:0.412 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site