I was about to say that cxgbe still uses it, but it looks like that was just changed in r340465. So yes, lets get rid of it.

• Fixed a pre-existing bug where, when receiving small packets, rx clusters were not unmapped, yet they were re-mapped when refilling the ring. This was fixed by keeping track of the bus address in ifsd_ba, and simply re-using them rather than re-doing the virt to bus mapping

Thanks Olivier. 5% is about what I had expected. I think I see a way to improve that though. We seem to be doing repeated virt to phys translation on clusters where we have copied out a small mbuf on the rx side in iflib_rxd_pkt_get(). We call rxd_frag_to_sd() with a FALSE arg, to prevent unmapping. Yet in _iflib_fl_refill(), we seem to always do the mapping, even when we do not re-allocate clusters. This is one bit that's going to be more expensive on low-end boxes, since it will now result in a busdma callback function being called. I think this is an actual bug that would impact systems w/IOMMUs

In D17665#377526, @np wrote:

Stepping back for a second, are we going to get to a point where we can make malloc() and uma_zalloc() use the current thread's domainset policy, rather than one derived from the kernel object?

FWIW, i have patched both of these changes (this + D17492) into the upstream ck git repo, and run them through the CK regression tests for epoch in userpace on my 32-core/64-thread amd, and they passed.

In D17416#372763, @markj wrote:

In D17416#372648, @gallatin wrote:

You mention kstacks. I have not gone through the rest of your reviews, but I was wondering if you were working on affinitizing kstacks. Did you plan to break the cache out by domain, or drop it for affinitized kstack allocations? The default is so undersized these days, we're mostly not getting the benefit of the cache anyway (and the cache might be pessimal, since it is protected by a global lock).

I wasn't working on affinity. Rather, I want to ensure that the kstack allocation policy allows allocations from any domain, ensuring that we can permit kstack swapins so long as at least one domain has some free pages. See D17304; it's really just a bug fix for 12.0.

I haven't thought much about the problems you listed. Do you have a proposal?

You mention kstacks. I have not gone through the rest of your reviews, but I was wondering if you were working on affinitizing kstacks. Did you plan to break the cache out by domain, or drop it for affinitized kstack allocations? The default is so undersized these days, we're mostly not getting the benefit of the cache anyway (and the cache might be pessimal, since it is protected by a global lock).

Do we really need a new malloc variant? Couldn't this be done with a new malloc flag that was specific to malloc_domain(). Something like M_ALTOK or something? (or maybe M_EXACT if you want the default to be the other way around, and have malloc_domain() fall back by default)

This was committed as r339043. Due to a cut and paste error, the wrong review was linked from the commit message, so the review was not auto-closed.

In D16836#368220, @markj wrote:

kmem_back() now also needs updating.

• Fixed spelling errors pointed out by alc
• Updated to account for recent VM changes:
  • added empty domain guard in kmm_back()
  • fixed conflict in keg_fetch_slab() after r338755

Added check for empty domains in uma_large_malloc_domain(), and removed added blank line, as pointed out by Mark

In D16836#365423, @markj wrote:

We already have code to renumber NUMA domains to avoid holes in the domain ID space (renumber_domains() in srat.c). Wouldn't it be simpler to apply a similar approach to empty domains, or is there some reason that won't work?

FWIW, as I mentioned in private email, the testing went fine. I verified that there were no apparent mem leaks, and that in_pcblbgroup_free_deferred() was called when I bounced nginx several times on a heavily loaded (> 90Gb/s) box.

We've had it in our config at Netflix for so long that I forgot that it was not in GENERIC..

For what it is, Van's birthday might be a better choice. Eg, some non-valid pointer that would cause free or mfree to panic rather than accept it and corrupt data.

Sorry, having the ring pointer in the ring is just so odd.. Can you explain why it is there? Maybe it would be better to just not have the ring pointer in the ring and not have to have all these special cases.

What keeps the normal, non-IFC_QFLUSH from hitting this condition? Is the txq pointer included in r->size?

In D16836#359533, @markj wrote:

I haven't had much of a chance to review this yet, but I wanted to test an "options NUMA" kernel on a system with an empty domain (dual socket Haswell xeon with only one DIMM installed at the moment). This patch worked fine for me. Thanks!

Thanks for the clarification on the non-offset range!

Thank you so much for the pointer to the docs!!! It is much nicer to write from real docs, rather than crib from undocumented changes in another project.

In general, I looked around at ixlv.c, and it looks like there are many functions for the main pf which are identical, or nearly identical for the VF. Can we please work on collapsing them down to common code?

Thank for doing this!

I ran this on a Netflix 100g box. I observed no measurable difference in CPU time. So I think this patch is "neutral" for the perspective of our (mostly kernel) workload.

In D15937#337221, @kbowling wrote:

I've deployed a variant of this widely at LLNW on the default stack as well. I think you can garbage collect sbsndptr() from the tree.

I added Hans since it is mostly his code we are factoring out.

if @jch cannot run his real workload, what about running a synthetic test that creates / tears down many connections per second? Eg, something like many copies of netperf -t TCP_CC ?

You might want to go for some middle ground here. 1ms is a bit much (even for us).

Sure.. Those checks for TCP in the TSO case should probably turn into asserts eventually..

If people want to use ethernet entropy harvesting, can we do something to make it more useful in a separate change? I was going to initially suggest the ether dst addr, but that's not very random either.

This is the sparse detect I'm using. Note how it walks the header, and then the TSO by packet on the wire.

Somehow my last comment got lost. With real Netflix traffic, the sparse detection logic is not sufficient. When we have kernel TLS, which inserts 13 and 16 byte mbufs around TLS records, we hit MDDs regularly. I think you need to walk the packet stream, not the DMA descriptors, so that you keep the same segmentation used by the hardware. I re-wrote the sparse detection to do this, and our MDDs went away.

In D15558#328462, @gallatin wrote:

In D15558#328453, @sbruno wrote:

Was this the patch that we discussed on our call? Does this fix your TX checksum problems on IXL?

Yes and Yes.

Unfortunately, I've now proceeded to the "entire box hangs" portion of the game. Even serial console break-to-debugger is ignored. I'm going to try NMIs next..

In D15558#328453, @sbruno wrote:

Was this the patch that we discussed on our call? Does this fix your TX checksum problems on IXL?

Looks good for content to me.

Under a heavy UDP packet flood this helps quite a bit.

Looks awesome. My only issue is that I'd strongly prefer that the STAILQ_HEAD / STAILQ_INIT / STAILQ_ENTRY macros be prefixed with CK_ so that readers realize that these lists are used with epochs, and cannot be safely used with the normal STAILQ macros. I tried to point out most of them, but I may have missed a few.

It would be nice to have this patch together with at least one example of a caller and one example of a NIC driver implementing the API.