> >> >> > > >> >> >6. Handling page cache in the guest The memory used for page > >> >> >cache in the guest will change depends on the workload, if guest > >> >> >run some block IO intensive work load, there will > >> >> > >> >> Would this improvement benefit a lot when guest only has little free > page? > >> > > >> >Yes, the improvement is very obvious. > >> > > >> > >> Good to know this. > >> > >> >> In your Performance data Case 2, I think it mimic this kind of case. > >> >> While the memory consuming task is stopped before migration. If it > >> >> continues, would we still perform better than before? > >> > > >> >Actually, my RFC patch didn't consider the page cache, Roman raised > >> >this > >> issue. > >> >so I add this part in this doc. > >> > > >> >Case 2 didn't mimic this kind of scenario, the work load is an > >> >memory consuming work load, not an block IO intensive work load, so > >> >there are not many page cache in this case. > >> > > >> >If the work load in case 2 continues, as long as it not write all > >> >the memory it allocates, we still can get benefits. > >> > > >> > >> Sounds I have little knowledge on page cache, and its relationship > >> between free page and I/O intensive work. > >> > >> Here is some personal understanding, I would appreciate if you could > >> correct me. > >> > >> +---------+ > >> |PageCache| > >> +---------+ > >> +---------+---------+---------+---------+ > >> |Page |Page |Free Page|Page | > >> +---------+---------+---------+---------+ > >> > >> Free Page is a page in the free_list, PageCache is some page cached > >> in CPU's cache line? > > > >No, page cache is quite different with CPU cache line. > >" In computing, a page cache, sometimes also called disk cache,[2] is a > >transparent cache for the pages originating from a secondary storage > device such as a hard disk drive (HDD). > > The operating system keeps a page cache in otherwise unused portions > >of the main memory (RAM), resulting in quicker access to the contents > >of cached pages and overall performance improvements " > >you can refer to https://en.wikipedia.org/wiki/Page_cache > >for more details. > > > > My poor knowledge~ Should google it before I imagine the meaning of the > terminology. > > If my understanding is correct, the Page Cache is counted as Free Page, while > actually we should migrate them instead of filter them.
No, the Page Cache is not counted as Free Page ... Liang
