> From: Bruce Richardson [mailto:[email protected]] > Sent: Wednesday, 10 December 2025 18.01 > > On Mon, Aug 11, 2025 at 02:47:17PM +0200, Morten Brørup wrote: > > > From: Morten Brørup [mailto:[email protected]] > > > Sent: Tuesday, 24 June 2025 08.13 > > > > > > When fast releasing mbufs, the mbufs are not accessed, so do not > prefetch > > > them. > > > This saves a mbuf load operation for each fast released TX mbuf. > > > > > > When fast release of mbufs is enabled for a TX queue, cache the > mbuf > > > mempool pointer in the TX queue structure. > > > This saves one mbuf load operation for each burst of fast released > TX > > > mbufs. > > > > > > The txep->mbuf pointer is not used after the mbuf has been freed, > so do > > > not reset the pointer. > > > This saves a txep store operation for each TX mbuf freed. > > > > > > Signed-off-by: Morten Brørup <[email protected]> > > > --- > > > > After further consideration, I think this patch should be split in > two: > > 1. Remove superfluous code: prefetching mbufs and resetting txep- > >mbuf pointers. > > 2. Cache the mbuf mempool pointer for FAST_FREE. > > > Hi Morten, > > any plans for a new version of this patch (split or otherwise)? This is > popped up again on my list in patchwork and want to decide what to do > with > it for this release. :-) > > /Bruce
I'll give it another shot. I took another look at it today, and it looks like the txep->mbuf (i.e. sw_ring[].mbuf) is used by other cleanup functions, so not NULL'ing it needs more detailed review. Anyway, prefetching the mbufs is a complete waste for fast free, where the mbufs are not being accessed at all. So there's still something to gain here. Also, my assumption that txq->offloads is hotter than txq->fast_free_mp seems not to hold either, so I'll play around with that too. I'm considering sending a series of patches with very small steps, so the individual changes are easy to review. -Morten
