Messages in this thread | | | Date | Fri, 3 Mar 2023 12:31:48 +0100 | Subject | Re: [PATCH bpf-next v1 0/2] xdp: recycle Page Pool backed skbs built from XDP frames | From | Alexander Lobakin <> |
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From: Jesper Dangaard Brouer <jbrouer@redhat.com> Date: Fri, 3 Mar 2023 11:39:06 +0100
> > On 01/03/2023 17.03, Alexander Lobakin wrote: >> Yeah, I still remember that "Who needs cpumap nowadays" (c), but anyway. >> >> __xdp_build_skb_from_frame() missed the moment when the networking stack >> became able to recycle skb pages backed by a Page Pool. This was making > ^^^^^^^^^ > When talking about page_pool, can we write "page_pool" instead of > capitalized "Page Pool", please. I looked through the git log, and here > we all used "page_pool".
Ah okay, no prob :D Yeah, that's probably more correct. "Page Pool" is the name of the API, while page_pool is an entity we create via page_pool_create().
> >> e.g. cpumap redirect even less effective than simple %XDP_PASS. veth was >> also affected in some scenarios. > > Thanks for working on closing this gap :-) > >> A lot of drivers use skb_mark_for_recycle() already, it's been almost >> two years and seems like there are no issues in using it in the generic >> code too. {__,}xdp_release_frame() can be then removed as it losts its >> last user. >> Page Pool becomes then zero-alloc (or almost) in the abovementioned >> cases, too. Other memory type models (who needs them at this point) >> have no changes. >> >> Some numbers on 1 Xeon Platinum core bombed with 27 Mpps of 64-byte >> IPv6 UDP: > > What NIC driver?
IAVF with XDP, the series adding XDP support will be sent in a couple weeks, WIP can be found on my open GH[0].
> >> >> Plain %XDP_PASS on baseline, Page Pool driver: >> >> src cpu Rx drops dst cpu Rx >> 2.1 Mpps N/A 2.1 Mpps >> >> cpumap redirect (w/o leaving its node) on baseline: >> >> 6.8 Mpps 5.0 Mpps 1.8 Mpps >> >> cpumap redirect with skb PP recycling: >> >> 7.9 Mpps 5.7 Mpps 2.2 Mpps +22% >> > > It is of cause awesome, that cpumap SKBs are faster than normal SKB path.
That's the point of cpumap redirect, right? You separate NAPI poll / IRQ handling from the skb networking stack traveling to a different CPU, including page freeing (or recycling). That takes a lot of load from the source CPU. 0.1 Mpps is not the highest difference I got, cpumap redirect can boost up to 0.5 Mpps IIRC.
> I do wonder where the +22% number comes from?
(2.2 - 1.8) / 1.8 * 100%. I compare baseline cpumap redirect before/after here :)
> >> Alexander Lobakin (2): >> xdp: recycle Page Pool backed skbs built from XDP frames >> xdp: remove unused {__,}xdp_release_frame() >> >> include/net/xdp.h | 29 ----------------------------- >> net/core/xdp.c | 19 ++----------------- >> 2 files changed, 2 insertions(+), 46 deletions(-) >> >
There's a build failure on non-PP systems due to skb_mark_for_recycle() being declared only when CONFIG_PAGE_POOL is set. I'll spin v2 in a bit.
[0] https://github.com/alobakin/linux/commits/iavf-xdp
Thanks, Olek
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