From: Eric Dumazet <dada1@cosmosbay•com>
To: Antoine Zen-Ruffinen <antoine.zen@gmail•com>
Cc: netdev@vger•kernel.org, linux-net@vger•kernel.org,
netfilter-devel@vger•kernel.org, patrik.arlos@bth•se
Subject: Re: Problem with frame time stamping
Date: Tue, 13 Nov 2007 11:55:35 +0100 [thread overview]
Message-ID: <473982A7.6040409@cosmosbay.com> (raw)
In-Reply-To: <2cbbd8de0711130239j67127e1cxf312033aee1ddd5a@mail.gmail.com>
Antoine Zen-Ruffinen a écrit :
> This is exactly my problem : The driver of the network card I am using
> (see rt2x00.serialmonkey.com) do the minimum in the hardware interrupt
> (not filling skb->tstamp). Then netif_rx() is called later using a
> tasklet (also not filling skb->tstamp). As it seem to me (maybe I am
> wrong, if so please tell), the elapse time between the actual frame
> arrival and the time where netif_rx() do net_timestamp(skb) is not
> predicable !?
>
> Else, I would like to thank you to spend time helping me.
>
>
>
A tasklet could process the skb much later than corresponding IRQ,
depending on various things
(other tasks/softirqs on system with higher priorities). So yes, it is
not predictable at all.
Usually it doesnt matter, but if your business depends on precise tstamps,
then just do skb->tstamp = ktime_get_real(); in IRQ handler (but it will
slow it a bit,
depending on how fast is ktime_get_real() on the target machine)
netif_rx() wont overwrite it.
skb = dev_alloc_skb(desc.size + NET_IP_ALIGN);
if (!skb)
return;
skb->tstamp = ktime_get_real(); /* do it before other copies */
skb_reserve(skb, NET_IP_ALIGN);
skb_put(skb, desc.size);
memcpy(skb->data, entry->data_addr, desc.size);
...
next prev parent reply other threads:[~2007-11-13 10:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-12 15:42 Problem with frame time stamping Antoine Zen-Ruffinen
2007-11-12 16:47 ` Eric Dumazet
2007-11-13 10:07 ` Antoine Zen-Ruffinen
2007-11-13 10:27 ` Eric Dumazet
2007-11-13 10:39 ` Antoine Zen-Ruffinen
2007-11-13 10:43 ` Antoine Zen-Ruffinen
2007-11-13 10:55 ` Eric Dumazet [this message]
2007-11-13 12:34 ` Antoine Zen-Ruffinen
2007-11-13 13:13 ` Eric Dumazet
2007-11-13 14:46 ` Antoine Zen-Ruffinen
2007-11-13 10:36 ` Eric Dumazet
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