On Thu, May 15, 2008 at 4:24 AM, Chris Webb <[EMAIL PROTECTED]> wrote:
> Since you mention trying socketfilter, I've attached a newer version of my
> socketfilter patch which I've recently sent to Ed. This is functionally the
> same as the earlier one against vblade-15, but pulls out the BPF code from
> linux.c and freebsd.c into a single bpf.c and loses the dependency on
> libpcap headers, as he requested. As far as I can tell, with this patch
> applied, a collection of vblades should perform identically to qaoed but
> with less complex code. (If any performance gap remains, I'd like to know so
> I can fix it!)
>

I'll email you off line when I have time (probably in 2 weeks) to work
on providing validation of a test case for this.

> I've also attached a second patch which applies on top of the socketfilter
> patch and adds a number of options to vblade. In particular, -d for
> O_DIRECT, -s for O_SYNC, -r for read-only export and (now) -b for altering
> the advertised buffer count as you describe. I use this patch locally and it
> sounds like you might find it useful too.
>

Thanks! We'll be testing this along with the socketfilter patch. This
is much cleaner than what we are doing now.

> I've tested this modified vblade fairly carefully both on Linux and FreeBSD
> 7.0 and can confirm it compiles without warnings and runs fine on both
> supported platforms.
>
> When it comes to the AIO support I wrote, I found surprisingly little
> performance benefit from it despite the underlying block devices being much
> slower than the network. However, I'm linking against a userspace AIO
> implementation (in librt) rather than using kernel AIO support, and you are
> using much higher-end hardware than I have here. I would be very interested
> in any feedback you have from testing in your environment, especially if you
> try it with a kernel-backed AIO implementation.
>

It's not so much a performance benefit, it's a "make sure the data is
written to disk when non-AIO requests come in" thing. With AIO
support, we ought to be able to ensure that to a higher level.

> Best wishes,
>
> Chris.
>

Thanks,
Justin

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