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From: Eric Dumazet <dada1@cosmosbay.com>
To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Ulrich Drepper <drepper@gmail.com>,
	lkml <linux-kernel@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Ulrich Drepper <drepper@redhat.com>,
	Andrew Morton <akpm@osdl.org>, netdev <netdev@vger.kernel.org>,
	Zach Brown <zach.brown@oracle.com>,
	Christoph Hellwig <hch@infradead.org>,
	Chase Venters <chase.venters@clientec.com>,
	Johann Borck <johann.borck@densedata.com>
Subject: Re: [take19 1/4] kevent: Core files.
Date: Thu, 5 Oct 2006 14:09:31 +0200	[thread overview]
Message-ID: <200610051409.31826.dada1@cosmosbay.com> (raw)
In-Reply-To: <20061005105536.GA4838@2ka.mipt.ru>

On Thursday 05 October 2006 12:55, Evgeniy Polyakov wrote:
> On Thu, Oct 05, 2006 at 12:45:03PM +0200, Eric Dumazet (dada1@cosmosbay.com) 
> >
> > What is missing or not obvious is : If events are skipped because of
> > overflows, What happens ? Connections stuck forever ? Hope that
> > everything will restore itself ? Is kernel able to SIGNAL this problem to
> > user land ?
>
> Exisitng  code does not overflow by design, but can consume a lot of
> memory. I talked about the case, when there will be some limit on
> number of entries put into mapped buffer.

You still dont answer my question. Please answer the question.
Recap : You have a max of XXXX events queued. A network message come and 
kernel want to add another event. It cannot because limit is reached. How the 
User Program knows that this problem was hit ?


> It is the same.
> What if reing buffer was grown upto 3 entry, and is now empty, and we
> need to put there 4 entries? Grow it again?
> It can be done, easily, but it looks like a workaround not as solution.
> And it is highly unlikely that in situation, when there are a lot of
> event, ring can be empty.

I dont speak of re-allocation of ring buffer. I dont care to allocate at 
startup a big enough buffer.

Say you have allocated a ring buffer of 1024*1024 entries.
Then you queue 100 events per second, and dequeue them immediatly.
No need to blindly use all 1024*1024 slots in the ring buffer, doing 
index = (index+1)%(1024*1024)



> epoll() does not have mmap.
> Problem is not about how many events can be put into the kernel, but how
> many of them can be put into mapped buffer.
> There is no problem if mmap is turned off.

So zap mmap() support completely, since it is not usable at all. We wont 
discuss on it.

  reply	other threads:[~2006-10-05 12:09 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <115a6230591036@2ka.mipt.ru>
2006-09-12  8:41 ` [take18 0/4] kevent: Generic event handling mechanism Evgeniy Polyakov
2006-09-12  8:41   ` [take18 1/4] kevent: Core files Evgeniy Polyakov
2006-09-12  8:41     ` [take18 2/4] kevent: poll/select() notifications Evgeniy Polyakov
2006-09-12  8:41       ` [take18 3/4] kevent: Socket notifications Evgeniy Polyakov
2006-09-12  8:41         ` [take18 4/4] kevent: Timer notifications Evgeniy Polyakov
2006-09-20  9:35 ` [take19 0/4] kevent: Generic event handling mechanism Evgeniy Polyakov
2006-09-20  9:35   ` [take19 1/4] kevent: Core files Evgeniy Polyakov
2006-09-20  9:35     ` [take19 2/4] kevent: poll/select() notifications Evgeniy Polyakov
2006-09-20  9:35       ` [take19 3/4] kevent: Socket notifications Evgeniy Polyakov
2006-09-20  9:35         ` [take19 4/4] kevent: Timer notifications Evgeniy Polyakov
2006-10-04  6:34     ` [take19 1/4] kevent: Core files Ulrich Drepper
2006-10-04  6:48       ` Evgeniy Polyakov
2006-10-04 17:57         ` Ulrich Drepper
2006-10-05  8:57           ` Evgeniy Polyakov
2006-10-05  9:56             ` Eric Dumazet
2006-10-05 10:21               ` Evgeniy Polyakov
2006-10-05 10:45                 ` Eric Dumazet
2006-10-05 10:55                   ` Evgeniy Polyakov
2006-10-05 12:09                     ` Eric Dumazet [this message]
2006-10-05 12:37                       ` Evgeniy Polyakov
2006-10-15 23:22                         ` Ulrich Drepper
2006-10-16  7:33                           ` Evgeniy Polyakov
2006-10-16 10:16                             ` Ulrich Drepper
2006-10-16 11:23                               ` Evgeniy Polyakov
2006-10-17  5:10                           ` Johann Borck
2006-10-17  5:59                             ` Chase Venters
2006-10-17 10:42                               ` Evgeniy Polyakov
2006-10-17 13:12                                 ` Chase Venters
2006-10-17 13:35                                   ` Evgeniy Polyakov
2006-10-17 10:39                             ` Evgeniy Polyakov
2006-10-17 13:19                               ` Eric Dumazet
2006-10-17 13:42                                 ` Evgeniy Polyakov
2006-10-17 13:52                                   ` Eric Dumazet
2006-10-17 14:07                                     ` Evgeniy Polyakov
2006-10-17 14:25                                       ` Eric Dumazet
2006-10-17 15:09                                         ` Evgeniy Polyakov
2006-10-17 15:32                                           ` Eric Dumazet
2006-10-17 16:01                                             ` Evgeniy Polyakov
2006-10-17 16:26                                               ` Eric Dumazet
2006-10-17 16:35                                                 ` Evgeniy Polyakov
2006-10-17 16:45                                                   ` Eric Dumazet
2006-10-18  4:10                                                     ` Evgeniy Polyakov
2006-10-18  4:45                                                       ` Eric Dumazet
2006-10-17 15:33                                         ` Hans Henrik Happe
2006-10-05 14:01                 ` Hans Henrik Happe
2006-10-05 14:15                   ` Evgeniy Polyakov
2006-10-05 15:07                     ` Hans Henrik Happe
2006-09-22 19:22   ` [take19 0/4] kevent: Generic event handling mechanism Andrew Morton
2006-09-23  4:23     ` Evgeniy Polyakov
2006-10-04  6:09       ` Ulrich Drepper
2006-10-04  6:10         ` Ulrich Drepper
2006-10-04  6:27           ` Evgeniy Polyakov
2006-10-04  6:24         ` Evgeniy Polyakov
2006-09-26 15:54     ` Christoph Hellwig
2006-09-27  4:46       ` Evgeniy Polyakov
2006-09-27 15:09   ` Evgeniy Polyakov
2006-10-04  4:50     ` Ulrich Drepper
2006-10-04  4:55       ` Evgeniy Polyakov
2006-10-04  7:33         ` Ulrich Drepper
2006-10-04  7:48           ` Evgeniy Polyakov
2006-10-04 17:20             ` Ulrich Drepper
2006-10-05  9:02               ` Evgeniy Polyakov
2006-10-05 14:45                 ` Ulrich Drepper
2006-10-06  8:36                   ` Evgeniy Polyakov
2006-10-15 22:43                     ` Ulrich Drepper
2006-10-16  7:23                       ` Evgeniy Polyakov
2006-10-16  9:59                         ` Ulrich Drepper
2006-10-16 10:38                           ` Evgeniy Polyakov

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