On Fri, 2005-07-15 at 17:23 +0900, Tejun Heo wrote: > Badari Pulavarty wrote: ... > >> I don't know why you wanna relax the alignment requirement, but > >> wouldn't it be easier to just write/use block-aligned allocator for > >> such buffers? It will even make the program more portable. > >> > > > > I can imagine a reason for relaxing the alignment. I keep getting asked > > whether we can do "O_DIRECT mount option". Database folks wants to > > make sure all the access to files in a given filesystem are O_DIRECT > > (whether they are accessing or some random program like ftp, scp, cp > > are acessing them). This was mainly to ensure that buffered accesses to > > the file doesn't polute the pagecache (while database is using O_DIRECT > > access). Seems like a logical request, but not easy to do :( > > > > Thanks, > > Badari > > I don't know much about VM, but, if that's necessary, I think that > limiting pagecache size per mounted fs (or by some other applicable > category) is easier/more complete approach. After all, you cannot mmap > w/ O_DIRECT and many programs (gcc, ld come to mind) mmap large part of > their memory usage.
I agree. I guess for mmap()ed access we can kick it back to buffered mode. I don't think limiting pagecache use per filesystem is an acceptable option. In fact, database folks exactly want this - to limit the pagecache use by filesystems - but I don't think its right thing to do, so I am trying to propose mount O_DIRECT as an alternative (if its feasible). Thanks, Badari - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
