Confirming that this is just mlx5 issue, intel is fine. I just did a quick test with disabled[0] Spectre v2 mitigations. The performance remains the same, no difference at all. Sam. [0]: $ cat /sys/devices/system/cpu/vulnerabilities/spectre_v2 Vulnerable; IBPB: disabled; STIBP: disabled; PBRSB-eIBRS: Vulnerable; BHI: Vulnerable On Wed, Jul 24, 2024 at 5:48 PM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > Carolina Jubran <cjubran@xxxxxxxxxx> writes: > > > On 22/07/2024 12:26, Dragos Tatulea wrote: > >> On Sun, 2024-06-30 at 14:43 +0300, Tariq Toukan wrote: > >>> > >>> On 21/06/2024 15:35, Samuel Dobron wrote: > >>>> Hey all, > >>>> > >>>> Yeah, we do tests for ELN kernels [1] on a regular basis. Since > >>>> ~January of this year. > >>>> > >>>> As already mentioned, mlx5 is the only driver affected by this regression. > >>>> Unfortunately, I think Jesper is actually hitting 2 regressions we noticed, > >>>> the one already mentioned by Toke, another one [0] has been reported > >>>> in early February. > >>>> Btw. issue mentioned by Toke has been moved to Jira, see [5]. > >>>> > >>>> Not sure all of you are able to see the content of [0], Jira says it's > >>>> RH-confidental. > >>>> So, I am not sure how much I can share without being fired :D. Anyway, > >>>> affected kernels have been released a while ago, so anyone can find it > >>>> on its own. > >>>> Basically, we detected 5% regression on XDP_DROP+mlx5 (currently, we > >>>> don't have data for any other XDP mode) in kernel-5.14 compared to > >>>> previous builds. > >>>> > >>>> From tests history, I can see (most likely) the same improvement > >>>> on 6.10rc2 (from 15Mpps to 17-18Mpps), so I'd say 20% drop has been > >>>> (partially) fixed? > >>>> > >>>> For earlier 6.10. kernels we don't have data due to [3] (there is regression on > >>>> XDP_DROP as well, but I believe it's turbo-boost issue, as I mentioned > >>>> in issue). > >>>> So if you want to run tests on 6.10. please see [3]. > >>>> > >>>> Summary XDP_DROP+mlx5@25G: > >>>> kernel pps > >>>> <5.14 20.5M baseline > >>>>> =5.14 19M [0] > >>>> <6.4 19-20M baseline for ELN kernels > >>>>> =6.4 15M [4 and 5] (mentioned by Toke) > >>> > >>> + @Dragos > >>> > >>> That's about when we added several changes to the RX datapath. > >>> Most relevant are: > >>> - Fully removing the in-driver RX page-cache. > >>> - Refactoring to support XDP multi-buffer. > >>> > >>> We tested XDP performance before submission, I don't recall we noticed > >>> such a degradation. > >> > >> Adding Carolina to post her analysis on this. > > > > Hey everyone, > > > > After investigating the issue, it seems the performance degradation is > > linked to the commit "x86/bugs: Report Intel retbleed vulnerability" > > (6ad0ad2bf8a67). > > Hmm, that commit is from June 2022, and according to Samuel's tests, > this issue was introduced sometime between commits b6dad5178cea and > 40f71e7cd3c6 (both of which are dated in June 2023). Besides, if it was > a retbleed mitigation issue, that would affect other drivers as well, > no? Our testing only shows this regression on mlx5, not on the intel > drivers. > > > >>> I'll check with Dragos as he probably has these reports. > >>> > >> We only noticed a 6% degradation for XDP_XDROP. > >> > >> https://lore.kernel.org/netdev/b6fcfa8b-c2b3-8a92-fb6e-0760d5f6f5ff@xxxxxxxxxx/T/ > > That message mentions that "This will be handled in a different patch > series by adding support for multi-packet per page." - did that ever go > in? > > -Toke >
