On 05/01/2015 04:48 PM, Paolo Bonzini wrote:
On 01/05/2015 21:55, John Snow wrote:
Where it makes sense, use the new faster primitives.
For generally small reads/writes such as for the PRDT
and FIS packets, stick with the more wasteful but
easier to debug memread/memwrite.
For ahci-test;
With this patch:
real 0m4.802s
user 0m3.506s
sys 0m2.393s
Without this series:
real 0m14.171s
user 0m12.072s
sys 0m12.527s
The overhead of memread is 2, the overhead of base64 is 1.33, also
base64 should have a larger cost of computing each byte. It doesn't add up.
Could it be simply that calling qtest_send (and hence
vsnprintf+qemu_chr_fe_write_all, neither of which are speed demons) once
per byte is hideously inefficient? :)
Paolo
I wrote a loop to batch the ascii-hex conversion instead of letting
printf do it; then ran some more very, very scientific tests:
memset alone:
real 0m10.888s
user 0m9.303s
sys 0m9.146s
send-batching:
real 0m6.541s
user 0m5.027s
sys 0m4.941s
memset+batching+b64:
real 0m3.675s
user 0m2.582s
sys 0m1.718s
So it still seems as if the b64 batching is a strict improvement
speed-wise. I'll send the non-b64 batching patch separately later,
unless you have thoughts otherwise.
--js
