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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
