The often-NULL data arg to read_cache_page() and read_mapping_page()
functions is misdescribed as "destination for read data": no, it's the
first arg to the filler function, often struct file * to ->readpage().
Satisfy checkpatch.pl on those filler prototypes, and tidy up the
declarations in linux/pagemap.h.
Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently we are keeping faulted page locked throughout whole __do_fault
call (except for page_mkwrite code path) after calling file system's fault
code. If we do early COW, we allocate a new page which has to be charged
for a memcg (mem_cgroup_newpage_charge).
This function, however, might block for unbounded amount of time if memcg
oom killer is disabled or fork-bomb is running because the only way out of
the OOM situation is either an external event or OOM-situation fix.
In the end we are keeping the faulted page locked and blocking other
processes from faulting it in which is not good at all because we are
basically punishing potentially an unrelated process for OOM condition in
a different group (I have seen stuck system because of ld-2.11.1.so being
locked).
We can do test easily.
% cgcreate -g memory:A
% cgset -r memory.limit_in_bytes=64M A
% cgset -r memory.memsw.limit_in_bytes=64M A
% cd kernel_dir; cgexec -g memory:A make -j
Then, the whole system will live-locked until you kill 'make -j'
by hands (or push reboot...) This is because some important page in a
a shared library are locked.
Considering again, the new page is not necessary to be allocated
with lock_page() held. And usual page allocation may dive into
long memory reclaim loop with holding lock_page() and can cause
very long latency.
There are 3 ways.
1. do allocation/charge before lock_page()
Pros. - simple and can handle page allocation in the same manner.
This will reduce holding time of lock_page() in general.
Cons. - we do page allocation even if ->fault() returns error.
2. do charge after unlock_page(). Even if charge fails, it's just OOM.
Pros. - no impact to non-memcg path.
Cons. - implemenation requires special cares of LRU and we need to modify
page_add_new_anon_rmap()...
3. do unlock->charge->lock again method.
Pros. - no impact to non-memcg path.
Cons. - This may kill LOCK_PAGE_RETRY optimization. We need to release
lock and get it again...
This patch moves "charge" and memory allocation for COW page
before lock_page(). Then, we can avoid scanning LRU with holding
a lock on a page and latency under lock_page() will be reduced.
Then, above livelock disappears.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reported-by: Lutz Vieweg <lvml@5t9.de> Original-idea-by: Michal Hocko <mhocko@suse.cz> Cc: Michal Hocko <mhocko@suse.cz> Cc: Ying Han <yinghan@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joe Thornber [Tue, 26 Jul 2011 00:38:15 +0000 (10:38 +1000)]
Initial EXPERIMENTAL implementation of device-mapper thin provisioning
with snapshot support. The 'thin' target is used to create instances of
the virtual devices that are hosted in the 'thin-pool' target. The
thin-pool target provides data sharing among devices. This sharing is
made possible using the persistent-data library in the previous patch.
The main highlight of this implementation, compared to the previous
implementation of snapshots, is that it allows many virtual devices to
be stored on the same data volume, simplifying administration and
allowing sharing of data between volumes (thus reducing disk usage).
Another big feature is support for arbitrary depth of recursive
snapshots (snapshots of snapshots of snapshots ...). The previous
implementation of snapshots did this by chaining together lookup tables,
and so performance was O(depth). This new implementation uses a single
data structure so we don't get this degradation with depth.
For further information and examples of how to use this, please read
Documentation/device-mapper/thin-provisioning.txt
Signed-off-by: Joe Thornber <thornber@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Randy Dunlap [Tue, 26 Jul 2011 00:37:47 +0000 (10:37 +1000)]
General cleanups to kernel-parameters.txt:
- add missing $ARCH that are being used/referenced
- alphabetize the parameter restrictions list
- spell "IA-64" as listed in arch/ia64/Kconfig instead of "IA64"
- remove trailing whitespace
- use hyphen in 32-bit etc.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Stephen Boyd [Tue, 26 Jul 2011 00:37:47 +0000 (10:37 +1000)]
Usually kernel parameters are documented in kernel-parameters.txt
but user_debug is only documented in the Kconfig. Document the
option and point to the Kconfig help text for more info.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Russell King <linux@arm.linux.org.uk> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
projects / karo-tx-linux.git / log