On 02/26/2017 09:59 PM, Xiubo Li wrote: >> But, We likely don't want to release memory from the data area anyways >> while active, in any case. How about if we set a timer when active >> commands go to zero, and then reduce data area to some minimum if no new >> cmds come in before timer expires? > > If I understand correctly: for example, we have 1G(as the minimum) > data area and all blocks have been allocated and mapped to runner's > vma, then we extern it to 1G + 256M as needed. When there have no > active cmds and after the timer expires, will it reduce the data area > back to 1G ? And then should it release the reduced 256M data area's > memories ? > > If so, after kfree()ed the blocks' memories, it should also try to remove > all the ptes which are mapping this page(like using the try_to_umap()), > but something like try_to_umap() doesn't export for the modules. > > Without ummaping the kfree()ed pages' ptes mentioned above, then > the reduced 256M vma space couldn't be reused again for the runner > process, because the runner has already do the mapping for the reduced > vma space to some old physical pages(won't trigger new page fault > again). Then there will be a hole, and the hole will be bigger and bigger. > > Without ummaping the kfree()ed pages' ptes mentioned above, the > pages' reference count (page_ref_dec(), which _inc()ed in page fault) > couldn't be reduced back too. Let's ask people who will know... Hi linux-mm, TCM-User (drivers/target/target_core_user.c) currently uses vmalloc()ed memory to back a ring buffer that is mmaped by userspace. We want to move to dynamically mapping pages into this region, and also we'd like to unmap/free pages when idle. What's the right way to unmap? I see unmap_mapping_range() but that mentions an underlying file, which TCMU doesn't have. Or maybe zap_page_range()? But it's not exported. Any advice? Thanks in advance -- Regards -- Andy
