On 15/12/2015 23:33, Vincenzo Maffione wrote: > This patch slightly rewrites the code to reduce the number of accesses, since > many of them seems unnecessary to me. After this reduction, the bottleneck > jumps from 1 Mpps to 2 Mpps.
Very nice. Did you get new numbers with the rebase? That would help measuring the effect of removing variable-sized memcpy (I'll post the patches for this shortly; they're entirely in memory.h/exec.c so they're not virtio-specific). A rough measurement from "perf" says they're worth about 5%. Related to this, patch 3 introduces a variable-sized memcpy, because it switches from 2 virtio_stl_phys to 1 address_space_write. I'm curious if the effect of this individual patch is positive, negative or neutral. On the other hand, patches 1 and 2 are clear wins. Paolo > Patch is not complete (e.g. it still does not properly manage endianess, it is > not clean, etc.). I just wanted to ask if you think the idea makes sense, and > a proper patch in this direction would be accepted.
