Re: [Dovecot] pop3 TCP_CORK too late error

2010-10-14 Thread Timo Sirainen 
On Sat, 2010-10-09 at 21:33 -0700, Ryan Murray wrote:
 I was straceing a pop3 process and noticed that the TCP_CORK option
 isn't set soon enough:
 
 epoll_wait(8, {{EPOLLOUT, {u32=37481984, u64=37481984}}}, 38, 207) = 1
 write(41, iTxPBrNlaNFao+yQzLhuO4/+tQ5cuiKSe..., 224) = 224

http://hg.dovecot.org/dovecot-2.0/rev/f3aa8be626fa should fix this.

Re: [Dovecot] pop3 TCP_CORK too late error

2010-10-10 Thread Marcus Rueckert 
On 2010-10-09 21:33:11 -0700, Ryan Murray wrote:
 epoll_wait(8, {{EPOLLOUT, {u32=37481984, u64=37481984}}}, 38, 207) = 1
 write(41, iTxPBrNlaNFao+yQzLhuO4/+tQ5cuiKSe..., 224) = 224
 epoll_ctl(8, EPOLL_CTL_MOD, 41, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP,
 {u32=37481984, u64=37481984}}) = 0
 pread(19, AFABQAlAC0AJ\nQAUALQAUAFABQAlAC0AF..., 8192, 811008) = 8192
 setsockopt(41, SOL_TCP, TCP_CORK, [1], 4) = 0
 write(41, \r\nKUWtGCjKO5N8UbW5uYLZbS0nmaNi4ZB..., 4134) = 4134
*snip*
 setsockopt(41, SOL_TCP, TCP_CORK, [0], 4) = 0
 
 The TCP_CORK option should get set before the first call to write()
 there, rather than after the first pread().

there are 2 calls to setsocketopt for it. maybe you missed the first
one?

darix

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Re: [Dovecot] pop3 TCP_CORK too late error

2010-10-10 Thread Ryan Murray 
On Mon, 2010-10-11 at 03:30 +0200, Marcus Rueckert wrote:
 On 2010-10-09 21:33:11 -0700, Ryan Murray wrote:
  epoll_wait(8, {{EPOLLOUT, {u32=37481984, u64=37481984}}}, 38, 207) = 1
  write(41, iTxPBrNlaNFao+yQzLhuO4/+tQ5cuiKSe..., 224) = 224
  epoll_ctl(8, EPOLL_CTL_MOD, 41, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP,
  {u32=37481984, u64=37481984}}) = 0
  pread(19, AFABQAlAC0AJ\nQAUALQAUAFABQAlAC0AF..., 8192, 811008) = 8192
  setsockopt(41, SOL_TCP, TCP_CORK, [1], 4) = 0
  write(41, \r\nKUWtGCjKO5N8UbW5uYLZbS0nmaNi4ZB..., 4134) = 4134
 *snip*
  setsockopt(41, SOL_TCP, TCP_CORK, [0], 4) = 0
  
  The TCP_CORK option should get set before the first call to write()
  there, rather than after the first pread().
 
 there are 2 calls to setsocketopt for it. maybe you missed the first
 one?

One setting it on, and one setting it off, yes.  The point of TCP_CORK
is to set it on before _any_ write() calls, and off after the write
calls.  This allows the kernel to make TCP packets of MSS size,
regardless of the size of your write()s.  The write that occurs before
enabling the cork causes a  MSS size packet to be sent, which increases
the time spent waiting for ACKs.