On 06/27/2013 10:47 PM, Zheng Liu wrote: >> I've been doing some testing involving large amounts of >> page cache. It's quite painful to get hundreds of GB >> of page cache mapped in, especially when I am trying to >> do it in parallel threads. This is true even when the >> page cache is already allocated and I only need to map >> it in. The test: >> >> 1. take 160 16MB files >> 2. clone 160 threads, mmap the 16MB files, and either >> a. walk through the file touching each page > > Why not change MAP_POPULATE flag in mmap(2)? Now it is only for private > mappings. But maybe we could let it support shared mapping. Adding that support to mmap() will certainly _help_ some folks. But, anything that mmap()s something is taking mmap_sem for write. That means that threaded apps doing mmap()/munmap() frequently are _not_ scalable. IOW, a process needing to do a bunch of MAP_POPULATEs isn't parallelizable, but one using this mechanism would be. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>