Re: [Xen-devel] [PATCH net-next] pktgen: Fill the payload optionally with a pattern

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 26/06/14 01:54, David Miller wrote:
> From: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> Date: Tue, 24 Jun 2014 21:40:15 +0100
>
> > Introduces a new flag called PATTERN, which puts a non-periodic, predicatble
> > pattern into the payload. This was useful to reproduce an otherwise intermittent
> > bug in xen-netback [1], where checksum checking doesn't help.
> > The pattern is a repetition of " %lu", a series of increasing numbers divided by
> > space. The value of the number is the size of the preceding payload area. E.g.
> > " 1 3 5"..." 1000 1005 1010"
> > If the pattern is used, every frag will have its own page, unlike before, so it
> > needs more memory.
> >
> > [1] 5837574: xen-netback: Fix grant ref resolution in RX path
> >
> > Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> You are changing the page allocation strategy regardless of the pattern
> setting, this is undesirable.
>
> It may be significantly faster to use the same page for all the frags,
> and this is absolutely critical for pktgen usage where every nanosecond
> of performance counts.
If the PATTERN flag is not used, it always using the pages[0] page, so 
it falls back to the original way.
Zoli

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