On Thu, Mar 08, 2012 at 12:33:20AM +0400, Konstantin Khlebnikov wrote: > Zheng Liu wrote: > > > > > >On Monday, February 20, 2012, Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx <mailto:khlebnikov@xxxxxxxxxx>> wrote: > > > Zheng Liu wrote: > > >> > > >> Cc linux-kernel mailing list. > > >> > > >> On Sat, Feb 18, 2012 at 12:20:05AM +0400, Konstantin Khlebnikov wrote: > > >>> > > >>> Zheng Liu wrote: > > >>>> > > >>>> Hi all, > > >>>> > > >>>> Currently, we encounter a problem about page reclaim. In our product system, > > >>>> there is a lot of applictions that manipulate a number of files. In these > > >>>> files, they can be divided into two categories. One is index file, another is > > >>>> block file. The number of index files is about 15,000, and the number of > > >>>> block files is about 23,000 in a 2TB disk. The application accesses index > > >>>> file using mmap(2), and read/write block file using pread(2)/pwrite(2). We hope > > >>>> to hold index file in memory as much as possible, and it works well in Redhat > > >>>> 2.6.18-164. It is about 60-70% of index files that can be hold in memory. > > >>>> However, it doesn't work well in Redhat 2.6.32-133. I know in 2.6.18 that the > > >>>> linux uses an active list and an inactive list to handle page reclaim, and in > > >>>> 2.6.32 that they are divided into anonymous list and file list. So I am > > >>>> curious about why most of index files can be hold in 2.6.18? The index file > > >>>> should be replaced because mmap doesn't impact the lru list. > > >>> > > >>> There was my patch for fixing similar problem with shared/executable mapped pages > > >>> "vmscan: promote shared file mapped pages" commit 34dbc67a644f and commit c909e99364c > > >>> maybe it will help in your case. > > >> > > >> Hi Konstantin, > > >> > > >> Thank you for your reply. I have tested it in upstream kernel. These > > >> patches are useful for multi-processes applications. But, in our product > > >> system, there are some applications that are multi-thread. So > > >> 'references_ptes> 1' cannot help these applications to hold the data in > > >> memory. > > > > > > Ok, what if you mmap you data as executable, just to test. > > > Then these pages will be activated after first touch. > > > In attachment patch with per-mm flag with the same effect. > > > > > > >Hi Konstantin, > > > >Sorry for the delay reply. Last two weeks I was trying these two solutions > >and evaluating the impacts for the performance in our product system. > >Good news is that these two solutions both work well. They can keep > >mapped files in memory under mult-thread. But I have a question for > >the first solution (map the file with PROT_EXEC flag). I think this way is > >too tricky. As I said previously, these files that needs to be mapped only > >are normal index file, and they shouldn't be mapped with PROT_EXEC flag > >from the view of an application programmer. So actually the key issue is > >that we should provide a mechanism, which lets different file sets can be > >reclaimed separately. I am not sure whether this idea is useful or not. So > >any feedbacks are welcomed.:-). Thank you. > > > > Sounds good. Yes, PROT_EXEC isn't very usable and secure, per-mm flag not > very flexible too. I prefer setting some kind of memory pressure priorities > for each vma and inode. Probably we can sort vma and inodes into different > cgroup-like sets and balance memory pressure between them. > Maybe someone was thought about it... Thanks for your advices. About setting pressure priorities for each vma and inode, I will send a new mail to mailing list to discuss this problem. Maybe someone has some good ideas for it. ;-) Regards, Zheng -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>