Messages in this thread |  | | | Date | Wed, 29 Jun 2011 15:27:58 +0300 | | From | Avi Kivity <> | | Subject | Re: [PATCH v2 19/22] KVM: MMU: lockless walking shadow page table |
| |
On 06/29/2011 03:28 PM, Xiao Guangrong wrote: > On 06/29/2011 08:18 PM, Avi Kivity wrote: > > On 06/29/2011 02:50 PM, Xiao Guangrong wrote: > >> >> > > >> >> > I think we should do this unconditionally. The cost of ping-ponging the shared cache line containing reader_counter will increase with large smp counts. On the other hand, zap_page is very rare, so it can be a little slower. Also, less code paths = easier to understand. > >> >> > > >> >> > >> >> On soft mmu, zap_page is very frequently, it can cause performance regression in my test. > >> > > >> > Any idea what the cause of the regression is? It seems to me that simply deferring freeing shouldn't have a large impact. > >> > > >> > >> I guess it is because the page is freed too frequently, i have done the test, it shows > >> about 3219 pages is freed per second > >> > >> Kernbench performance comparing: > >> > >> the origin way: 3m27.723 > >> free all shadow page in rcu context: 3m30.519 > > > > I don't recall seeing such a high free rate. Who is doing all this zapping? > > > > You may be able to find out with the function tracer + call graph. > > > > I looked into it before, it is caused by "write flood" detected, i also noticed > some pages are zapped and allocation again and again, maybe we need to improve > the algorithm of detecting "write flood".
Ok. Let's drop the two paths, and put this improvement on the TODO instead.
-- error compiling committee.c: too many arguments to function
|  |