On 2017年02月28日 03:32, Andy Grover wrote:
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.
Hi linux-mm
For the TCMU case, the vm is not anonymous mapping. And still has
device file desc:
mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, dev->fd, 0);
If using the unmap_mapping_range() to do the dynamically maping,
is it okay ? Any other potential risks ?
Or the mentioned 'underlying file' is must one desk file ?
Thanks very much,
BRs
Xiubo
Any advice?
Thanks in advance -- Regards -- Andy
