* Gonglei (arei.gong...@huawei.com) wrote:
> On 2014/2/28 17:19, Dr. David Alan Gilbert wrote:
>
> > * Gonglei (Arei) (arei.gong...@huawei.com) wrote:
> >
> > Hi,
> >
> >> a. Optimization the xbzrle remarkable decrease the cache misses.
> >> The efficiency of compress increases more than fifty times.
> >> Before the patch set, the cache almost totally miss when the
> >> number of cache item less than the dirty page number. Now the
> >> hot pages in the cache will not be replaced by other pages.
> >
> > Nice, what do you use as your performance test case for xbzrle?
>
>
> The VM we used with 25G memory and 1Gbit nic. We run a test procedure
> in the vm, which as this:
>
> #include <stdio.h>
> #include <stdlib.h>
> #define PAGE_SIZE 4096
> void main(void)
> {
> char *p,*p1;
> long i,j,z;
>
> p = (char*)calloc(8*1024,1024*1024);
> if( p == NULL ){
> printf("fail to calloc \n");
> exit(1);
> }
> for(;;){
> p1 = p;
> for( i = 0 ; i < 8*1024 ; i++ ){
>
> for( j = 0 ; j < 1024*1024 ; j+=PAGE_SIZE ){
> *p1 = 0x55;
> p1+=PAGE_SIZE;
> }
> }
> }
> }
>
> finally,
> the results of without enable xbzrle: 115MB/sec
>
> using xbzrle without optimization (the size of cache 2G): 116MB/sec
>
> using xbzrle with our optimization (the size of cache 2G): 150MB/sec
Hmm yes, it's not a very realistic test is it.
Having said that, I've not managed to find a reallistic test people
can agree on; I was hoping you had one!
You're listing the differences in in MB/sec - what about total
time to migrate?
However, the other question is why your optimisation works well
with that test; is it just the CPU overhead that it's reducing
because it's not bothering to copy lots of stuff into the cache?
If that's all the guest is running, I can't see that it would
actually XBZRLE much - maybe just OS pages.
What do the 'info migrate' stats look like with/without your
optimisation - I'm interested in how many xbzrle pages are sent?
Dave
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
