Normally when importing a pool the space maps for all top level
vdevs are read from disk. The space maps will be required latter
when an allocation is performed and free blocks need to be located.
However, if the pool is imported readonly then we are guaranteed
that no allocations can occur. In this case the space maps need
not be loaded.. A similar argument can be made for the DTLs
(dirty time logs).
Because a pool import will fail if the space maps cannot be read.
The ability to safely ignore them makes it more likely that a
damaged pool can be imported readonly to recover its contents.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2831
The ability to use blanks is documented in zpool(8) and implemented
in module/zcommon/zfs_namecheck.c:valid_char().
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3083
The shell executes each command of a pipeline in a subshell,
thus $ret always had the same value after the while loop that
it had before the loop (http://mywiki.wooledge.org/BashFAQ/024),
signaling success even if some of the zpools could not be exported.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3083
5311 traverse_dnode may report success when it should not
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Andriy Gapon <avg@FreeBSD.org>
Reviewed by: Will Andrews <willa@spectralogic.com>
Approved by: Dan McDonald <danmcd@omniti.com>
References:
https://github.com/illumos/illumos-gate/commit/2a89c2chttps://www.illumos.org/issues/5311
Ported by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2970
The functions sa_find_sizes() and sa_build_layout() fail to account
for the additional 2 bytes of SA header space when calculating whether
a variable size attribute might spill over. They may consequently
determine that an attribute will fit in the bonus buffer along with a
spill block pointer, when in reality the attribute would be partially
overwritten by the spill block pointer if spill over occurs. This also
causes an inconsistency between the SA header size and the number of
variable size attributes in the layout, tripping an assertion when
debugging is on. The following reproducer demonstrates the problem.
ln -s $(perl -e 'print "z" x 20') file
setfattr -h -n trusted.foo -v $(perl -e 'print "z" x 200') file
Even though sa_find_sizes() computes the index of the attribute where
spill-over will occur, sa_build_layouts() discards the result and
recomputes it itself. As it turns out, both functions get it wrong.
Since this computation is awkward and, as history has shown, easy to
screw up, let's just do it in one place. This patch fixes the bug in
sa_find_sizes() and updates sa_build_layout() to use the result
computed there.
Also improve the comments in sa_find_sizes().
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#3070
When a dbuf is in the DB_EVICTING state it may no longer be on the
dn_dbufs list. In which case it's unsafe to call DB_DNODE_ENTER.
Therefore, any dbuf which is found in this safe must be skipped.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2553Closes#2495
After 53698a4, the following error occurs when make deb.
CCLD zed
../../lib/libzfs/.libs/libzfs.so: undefined reference to `get_system_hostid'
Add libzpool.la to zed/Makefile.am to fix this
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3080
If spl_hostid is set via module parameter, it's likely different from
gethostid(). Therefore, the userspace tool should read it first before
falling back to gethostid().
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3034
Currently, spl_hostid module parameter doesn't do anything, because it will
always be overwritten when calling into hostid_read().
Instead, we should only call into hostid_read() when spl_hostid is not zero,
just as the comment describes.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#427
Commit 7b2d78a046 fixed some improper uses
of snprintf(), however, in __dbuf_stats_hash_table_data() the return
value of snprintf is propagated to the caller. This caused spurious
ENOMEM errors when reading the dbufs kstat.
This commit causes the actual number of characters written to be returned.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3072
Commit log from FreeBSD:
We have observed that arc_release() can be called concurrently with a
l2arc in-flight write. Also, we have observed that arc_hdr_destroy()
can be called from arc_write_done() for a zio with ZIO_FLAG_IO_REWRITE
flag in similar circumstances.
Previously the l2arc headers would be freed while leaking their
associated compression buffers. Now the buffers are placed on
l2arc_free_on_write list for delayed freeing. This is similar to
what was already done to arc buffers that were supposed to be freed
concurrently with in-flight writes of those buffers.
In addition to fixing the discovered leaks this change also adds
some protective code to assert that a compression buffer associated
with a l2arc header is never leaked.
A new kstat l2_cdata_free_on_write is added. It keeps a count
of delayed compression buffer frees which previously would have
been leaks.
Tested by: Vitalij Satanivskij <satan@ukr.net> et al
Requested by: many
MFC after: 2 weeks
Sponsored by: HybridCluster / ClusterHQ
References:
https://illumos.org/issues/5222https://github.com/freebsd/freebsd/commit/b98f85dhttp://thread.gmane.org/gmane.os.freebsd.current/155757/focus=155781http://lists.open-zfs.org/pipermail/developer/2014-January/000455.htmlhttp://lists.open-zfs.org/pipermail/developer/2014-February/000523.html
Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3029
The zil_itx_create() function uses the vmem_alloc() allocator for
its buffers because when logging a write that buffer may be as large
as 64K. This is non-optimal because we may need to allocate many of
of these buffers and this interface has the potential to be slow.
Instead, use zio_data_buf_alloc() which is specifically designed to
be able to efficiently allocate a wide range of buffer sizes.
In addition, do some cleanup and use the zil_itx_destroy() function
to always free an itx structure. This way we're always sure the
right allocation functions are used. Notice that in the current
code kmem_free() and vmem_free() were both used. This happened to
work because these wrappers map to the same internal SPL function.
This was identified as a potential problem when a low-end memory
constrained system began logging the following warnings. There
was no deadlock here just repeated allocation failures resulting
in increased latency.
Possible memory allocation deadlock: size=65792 lflags=0x42d0
Pid: 20118, comm: kvm Tainted: P O 3.2.0-0.bpo.4-amd64
Call Trace:
[<ffffffffa040b834>] ? spl_kmem_alloc_impl+0x115/0x127 [spl]
[<ffffffffa040b84f>] ? spl_kmem_alloc_debug+0x9/0x36 [spl]
[<ffffffffa05d8a0b>] ? zil_itx_create+0x2d/0x59 [zfs]
[<ffffffffa05c71e6>] ? zfs_log_write+0x13a/0x2f0 [zfs]
[<ffffffffa05d41bc>] ? zfs_write+0x85b/0x9bb [zfs]
[<ffffffffa05e37ec>] ? zpl_aio_write+0xca/0x110 [zfs]
[<ffffffff811088e5>] ? do_sync_readv_writev+0xa3/0xde
[<ffffffff81108f41>] ? do_readv_writev+0xaf/0x125
[<ffffffff81109055>] ? sys_pwritev+0x55/0x9a
[<ffffffff813721d2>] ? system_call_fastpath+0x16/0x1b
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes#3059
For performance reasons the reworked kmem code maps vmem_alloc() to
kmalloc_node() for allocations less than spa_kmem_alloc_max. This
allows for more concurrency in the system and less contention of
the virtual address space. Generally, this is a good thing.
However, in the case when the kmalloc_node() fails it makes little
sense to retry it using kmalloc_node() again. It will likely fail
in exactly the same way. A smarter strategy is to abandon this
optimization and retry using spl_vmalloc() which is very likely
to succeed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#428
When _zed_event_add_var() was updated to be the common routine
for adding zedlet environment variables, an additional snprintf()
was added to the processing of each nvpair. This commit changes
_zed_event_add_nvpair() to directly call _zed_event_add_var()
for nvpair non-array types, thereby removing a superfluous call to
snprintf(). For consistency, the helper functions for converting
nvpair array types are similarly adjusted to add variables.
The _zed_event_value_is_hex() and _zed_event_add_var() functions have
been moved up in the file since forward declarations are not used,
but no changes have been made to these functions.
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3042
The zed_strings container stores strings in an AVL, but does not
check for duplicate strings being added. Within the AVL, strings
are indexed by the string value itself. avl_add() requires the node
being added must not already exist in the tree, and will assert()
if this is not the case.
This should not cause problems in practice. ZED uses this container
in two places. In zed_conf.c, it is used to store the names of
enabled zedlets as zed scans the zedlet directory listing; duplicate
entries cannot occur here since duplicate names cannot occur within
a directory. In zed_event.c, it is used to store the environment
variables (as "NAME=VALUE" strings) that will be passed to zedlets;
duplicate strings here should never happen unless there is a bug
resulting in a duplicate nvpair or environment variable.
This commit protects against adding a duplicate to a zed_strings
container by first checking for the string being added, and removing
the previous entry should one exist. This implements a "last one
wins" policy.
This commit also changes the prototype for zed_strings_add() to allow
the string key (by which it is indexed in the AVL) to differ from
the string value. By adding zedlet environment variables using the
variable name as the key, multiple adds for the same variable name
will result in only the last value being stored.
Finally, this commit routes all additions of zedlet environment
variables through the updated _zed_event_add_var(). This ensures
all zedlet environment variable names are properly converted.
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3042
Thank to commit a4430fce69 we're
now correctly returning EROFS when opening a zvol on a read-only
pool. Unfortunately, it looks like this causes us to trigger
some unexpected behavior by __blkdev_get().
In the failure case it's possible __blkdev_get() will call
__blkdev_put() for a bdev which was never successfully opened.
This results in us trying to close the device again and hitting
the NULL dereference.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1343
Rather than ASSERT when for some reason the readonly property of
a zvol can't be read cleanly handle the failure.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1343
This was caught by Clang. Clearly the intent of this code was
to explicitly ignore the return value.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3054
When importing pools with zpool import -aN there is inconsistent
behavior between '-d /dev/disk/by-id' (or another path) and
'-c /etc/zfs/zpool.cache'.
The difference in behavior is caused by zpool_find_import_cached()
returning an empty nvlist_t when there are no pools to import but
zpool_find_import_impl() returns NULL for the same situation. The
behavior of zpool_find_import_cached() is arguably more correct
because it allows returning NULL to be used for an error case and
not an empty set.
This change resolves the issue by updating get_configs() such that
it returns an empty set instead of NULL when no config is found.
The updated behavior will now always return 0 for this case.
$ zpool import -aN; echo $?
no pools available to import
0
$ zpool import -aN -d /var/tmp/; echo $?
no pools available to import
0
$ zpool import -aN -c /etc/zfs/zpool.cache; echo $?
no pools available to import
0
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2080
Add a port of arc_summary.py to ZFS on Linux, arc_summary.py is a
standard tool in FreeBSD and Illumos. The version of the script used
for the port originally came from FreeNAS.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#2920
The original script displayed tunable parameters using sysctl calls.
This patch modifies this by displaying tunable parameters found in
/sys/modules/zfs/parameters/. modinfo calls are used to capture
descriptions.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Ensure this script conforms to the projects style guidelines
by limiting line length to 80 columns.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Add a basic help option and usage description which is consistent
with arcstat.py and dbufstat.py. This also adds support for long
opts.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
The -p option is used to specify a specific page of output to be
displayed. If omitted, all output pages would be displayed.
arc_summary, as it stood, had really kludgy processing code for
processing the -p option. It relied on a try-except block which was
treated as an if statement and in normal operation would fail any time a
user didn't specify the -p option on the command line. When the
exception was thrown, the script would then display all output pages.
This happened whether the -p option was omitted or malformed. Thus, in
the principle use case, an exception would be raised in order to run the
script as desired. The same except code would be called regardless of
the exception, however, and malformed -p arguments would also cause the
script to execute.
Additionally, this required the function which handles the case where
all output pages were to be displayed, _call_all, to be potentially
called from several locations within main.
This commit refactors the option processing code to simplify it and make
it easier to catch runtime errors in the script. This is done by
specializing the try-except block to only have an exception when the -p
argument is malformed. When the -p option is correctly selected by the
user, it calls a function in the unSub array directly, which will only
display one page of output.
Finally in the context of this refactoring the page breaks have been
removed. Pages seem to have been added into the output in the FreeNAS
version of the script. This patch removes pages from the output to more
closely resemble the freebsd version of the script.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
1) Comment out stat sections whose kstats are not currently available
2) Port most of arc_summary to use spl kstats
3) Enable l2arc stats
5) Include compressed l2size
4) Minor style fixes / cleanup
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: cburroughs <chris.burroughs@gmail.com>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
The arc_summary script is a useful utility for administrators on
other ZFS platforms. It provides a quick and easy way to get a high
level view of the current ARC state.
Historically this was a perl script but it was rewritten in python
for FreeNAS. We've decided to adopt the python version instead of
the perl version for a few reasons.
1) ZoL has no existing perl dependencies, but it does have a python
dependency for scripts such as arcstat.py and dbufstat.py. Using
python for arc_summary.py helps us minimize dependencies.
2) Most major Linux distributions already depend heavily on python
for their core infrastructure. This means it's very likely to
be available even very early in the boot process.
Original source:
https://github.com/freenas/freenas/blob/master/gui/tools/arc_summary.py
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: cburroughs <chris.burroughs@gmail.com>
Signed-off-by: Kyle Blatter <kyleblatter@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
The sa_modify_attrs() function can add, remove or replace an SA.
The main loop in the function uses the index "i" to iterate over the
existing SAs and uses the index "j" for writing them into a new buffer
via SA_ADD_BULK_ATTR(). The write index, "j" is incremented on remove
(SA_REMOVE) operations which leads to a corruption in the new SA buffer.
This patch remove the increment for SA_REMOVE operations.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#3028
An attempt to debug zfsonlinux/zfs#2781 revealed that this code could be
simplified by using kmem_asprintf(). It is not clear that switching to
kmem_asprintf() addresses zfsonlinux/zfs#2781. However, switching to
kmem_asprintf() is cleanup that simplifies debugging such that it would
become clear that this is a bug in glibc should the issue persist.
It also brings this function almost back in sync with Illumos. This
was possible due to the recently reworked kmem code which allows us
to use KM_SLEEP in the same fashion as Illumos.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2791
Issue #2781
The kmem_vasprintf(), kmem_vsprintf(), kobj_open_file(), and vn_openat()
functions should all use the kmem_flags_convert() function to generate
the GFP_* flags. This ensures that they can be safely called in any
context and the correct flags will be used.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#426
The split count/scan shrinker callbacks introduced in 3.12 broke the
test for HAVE_SHRINK, effectively disabling the per-superblock shrinkers.
This patch re-enables the per-superblock shrinkers when the split shrinker
callbacks have been detected.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2975
The core motivation behind these changes is to minimize the
memory management differences between ZFS on Linux and other
platforms. This simplifies the process of porting changes to
Linux from other platforms. This is good for code quality
and is expected to reduce the number of defects accidentally
introduced due to porting. The following key Linux specific
changes have been reverted.
* KM_PUSHPAGE changed back to KM_SLEEP. All contexts where
it is unsafe to perform IO have been marked with PF_FSTRANS.
This context specific mechanism is now used exclusively
and the KM_PUSHPAGE mechanism has been retired.
* The KM_NODEBUG flag has been retired. Allocations larger
than 32K should use vmem_alloc()/vmem_free(). Depending
on the size of the allocation either kmalloc() or vmalloc()
will be used internally, but no warning will be printed.
* Pre-allocated vdev IO buffers and the dedicated SA spill
block cache have been retired. It is now safe and reliable
to allocate buffers of the needed size without fear of
deadlocking. This reduces our memory footprint and paves
the way for larger block sizes.
Depends on zfsonlinux/spl#414.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#2918
The SA spill_cache was originally introduced to avoid the need to
perform large kmem or vmem allocations. Instead a small dedicated
cache of preallocated SA buffers was kept.
This solution was viable while the maximum block size was limited
to 128K. But with the planned increase of the maximum block size
to 16M callers need to migrate to the zio_buf_alloc(). However,
they should be aware this interface is expected to change again
once the zio buffers are fully backed by scatter-gather lists.
Alternately, if the callers know these buffers will never be large
or be infrequently accessed they may kmem_alloc() or vmem_alloc()
the needed temporary space.
This change has the additional benegit of bringing the code back
inline with the upstream Illumos source.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Commit 86dd0fd added preallocated I/O buffers. This is no longer
required after the recent kmem changes designed to make our memory
allocation interfaces behave more like those found on Illumos. A
deadlock in this situation is no longer possible.
However, these allocations still have the potential to be expensive.
So a potential future optimization might be to perform then KM_NOSLEEP
so that they either succeed of fail quicky. Either case is acceptable
here because we can safely abort the aggregation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
As part of the spl kmem/vmem refactoring the kmem_cache_* functions
were split in to their own kmem_cache.h header. This was done in
part so that kmem_* consumers would not be forced to include the
kmem_cache_* functions which mask several Linux SLAB/SLAB functions.
Because of this we now much explicitly include kmem_cache.h in the
zfs_context.h. However, consumers such as Lustre which need access
to the KM_FLAGS but not the kmem_cache_* functions can now safely
just include kmem.h.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
By marking DMU transaction processing contexts with PF_FSTRANS
we can revert the KM_PUSHPAGE -> KM_SLEEP changes. This brings
us back in line with upstream. In some cases this means simply
swapping the flags back. For others fnvlist_alloc() was replaced
by nvlist_alloc(..., KM_PUSHPAGE) and must be reverted back to
fnvlist_alloc() which assumes KM_SLEEP.
The one place KM_PUSHPAGE is kept is when allocating ARC buffers
which allows us to dip in to reserved memory. This is again the
same as upstream.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Callers of kmem_alloc() which passed the KM_NODEBUG flag to suppress
the large allocation warning have been replaced by vmem_alloc() as
appropriate. The updated vmem_alloc() call will not print a warning
regardless of the size of the allocation.
A careful reader will notice that not all callers have been changed
to vmem_alloc(). Some have only had the KM_NODEBUG flag removed.
This was possible because the default warning threshold has been
increased to 32k. This is desirable because it minimizes the need
for Linux specific code changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The initial port of ZFS to Linux required a way to identify virtual
memory to make IO to virtual memory backed slabs work, so kmem_virt()
was created. Linux 2.6.25 introduced is_vmalloc_addr(), which is
logically equivalent to kmem_virt(). Support for kernels before 2.6.26
was later dropped and more recently, support for kernels before Linux
2.6.32 has been dropped. We retire kmem_virt() in favor of
is_vmalloc_addr() to cleanup the code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In order to avoid deadlocking in the IO pipeline it is critical that
pageout be avoided during direct memory reclaim. This ensures that
the pipeline threads can always make forward progress and never end
up blocking on a DMU transaction. For this very reason Linux now
provides the PF_FSTRANS flag which may be set in the process context.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The core motivation behind these changes is to minimize the
memory management differences between ZFS on Linux and other
platforms. This simplifies the process of porting changes to
Linux from other platforms. This is good for code quality
and is expected to reduce the number of defects accidentally
introduced due to porting.
The key reason this is now possible is due to the addition of
Linux features such as the thread-specific PF_FSTRANS bit which
was introduced for XFS.
This patch stack also performs some refactoring and cleanup
designed to make the code more maintainable and understandable.
Finally, in the context of making and testing these changes
several bugs were identified and resolved resulting in a
more robust implementation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#414
The __get_free_pages() function must be used in place of kmalloc()
to ensure the __GFP_COMP is strictly honored. This is due to
kmalloc() being layered on the generic Linux slab caches. It
wasn't until recently that all caches were created using __GFP_COMP.
This means that it is possible for a kmalloc() which passed the
__GFP_COMP flag to be returned a non-compound allocation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The kmem cache implementation always adds new slabs by dispatching a
task to the spl_kmem_cache taskq to perform the allocation. This is
done because large slabs must be allocated using vmalloc(). It is
possible these allocations will block on IO because the GFP_NOIO flag
is not honored. This can result in a deadlock.
Therefore, a deadlock detection strategy was implemented to deal with
this case. When it is determined, by timeout, that the spl_kmem_cache
thread has deadlocked attempting to add a new slab. Then all callers
attempting to allocate from the cache fall back to using kmalloc()
which does honor all passed flags.
This logic was correct but an optimization in the code allowed for a
deadlock. Because only slabs backed by vmalloc() can deadlock in the
way described above. An optimization was made to only invoke this
deadlock detection code for vmalloc() backed caches. This had the
advantage of making it easy to distinguish these objects when they
were freed.
But this isn't strictly safe. If all the spl_kmem_cache threads end
up deadlocked than we can't grow any of the other caches either. This
can once again result in a deadlock if memory needs to be allocated
from one of these other caches to ensure forward progress.
The fix here is to remove the optimization which limits this fall back
allocation stratagy to vmalloc() backed caches. Doing this means we
may need to take the cache lock in spl_kmem_cache_free() call path.
But this small cost can be mitigated by ignoring objects with virtual
addresses.
For good measure the default number of spl_kmem_cache threads has been
increased from 1 to 4, and made tunable. This alone wouldn't resolve
the original issue since it's still possible for all the threads to be
deadlocked. However, it does help responsiveness by ensuring that a
single deadlocked spl_kmem_cache thread doesn't block allocations from
other caches until the timeout is reached.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change is designed to improve the memory utilization of
slabs by more carefully setting their size. The way the code
currently works is problematic for slabs which contain large
objects (>1MB). This is due to slabs being unconditionally
rounded up to a power of two which may result in unused space
at the end of the slab.
The reason the existing code rounds up every slab is because it
assumes it will backed by the buddy allocator. Since the buddy
allocator can only performs power of two allocations this is
desirable because it avoids wasting any space. However, this
logic breaks down if slab is backed by vmalloc() which operates
at a page level granularity. In this case, the optimal thing to
do is calculate the minimum required slab size given certain
constraints (object size, alignment, objects/slab, etc).
Therefore, this patch reworks the spl_slab_size() function so
that it sizes KMC_KMEM slabs differently than KMC_VMEM slabs.
KMC_KMEM slabs are rounded up to the nearest power of two, and
KMC_VMEM slabs are allowed to be the minimum required size.
This change also reduces the default number of objects per slab.
This reduces how much memory a single cache object can pin, which
can result in significant memory saving for highly fragmented
caches. But depending on the workload it may result in slabs
being allocated and freed more frequently. In practice, this
has been shown to be a better default for most workloads.
Also the maximum slab size has been reduced to 4MB on 32-bit
systems. Due to the limited virtual address space it's critical
the we be as frugal as possible. A limit of 4M still lets us
reasonably comfortably allocate a limited number of 1MB objects.
Finally, the kmem:slab_small and kmem:slab_large SPLAT tests
were extended to provide better test coverage of various object
sizes and alignments. Caches are created with random parameters
and their basic functionality is verified by allocating several
slabs worth of objects.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reduce the threshold for detecting a kmem cache deadlock by 10x
from HZ to HZ/10. The reduced value is still several orders of
magnitude large enough to avoid being triggered incorrectly. By
reducing it we allow the system to resolve the issue more quickly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The spl-module-parameters(5) was not kept up to date. Refresh
the man page so that it lists all the possible module options,
describes what the do, and justify why the default values are
set they way the are.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Many people have noticed that the kmem cache implementation is slow
to release its memory. This patch makes the reclaim behavior more
aggressive by immediately freeing a slab once it is empty. Unused
objects which are cached in the magazines will still prevent a slab
from being freed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The comment above the Linux 3.16 kernel's clear_bit() states:
/**
* clear_bit - Clears a bit in memory
* @nr: Bit to clear
* @addr: Address to start counting from
*
* clear_bit() is atomic and may not be reordered. However, it does
* not contain a memory barrier, so if it is used for locking purposes,
* you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
* in order to ensure changes are visible on other processors.
*/
This comment does not make sense in the context of x86 because x86 maps the
operations to barrier(), which is a compiler barrier. However, it does make
sense to me when I consider architectures that reorder around atomic
instructions. In such situations, a processor is allowed to execute the
wake_up_bit() before clear_bit() and we have a race. There are a few
architectures that suffer from this issue.
In such situations, the other processor would wake-up, see the bit is still
taken and go to sleep, while the one responsible for waking it up will
assume that it did its job and continue.
This patch implements a wrapper that maps smp_mb__{before,after}_atomic() to
smp_mb__{before,after}_clear_bit() on older kernels and changes our code to
leverage it in a manner consistent with the mainline kernel.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The port of XFS to Linux introduced a thread-specific PF_FSTRANS bit
that is used to mark contexts which are processing transactions. When
set, allocations in this context can dip into kernel memory reserves
to avoid deadlocks during writeback. Linux 3.9 provided the additional
PF_MEMALLOC_NOIO for disabling __GFP_IO in page allocations, which XFS
began using in 3.15.
This patch implements hooks for marking transactions via PF_FSTRANS.
When an allocation is performed in the context of PF_FSTRANS, any
KM_SLEEP allocation is transparently converted to a GFP_NOIO allocation.
Additionally, when using a Linux 3.9 or newer kernel, it will set
PF_MEMALLOC_NOIO to prevent direct reclaim from entering pageout() on
on any KM_PUSHPAGE or KM_NOSLEEP allocation. This effectively allows
the spl_vmalloc() helper function to be used safely in a thread which
is responsible for IO.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This patch achieves the following goals:
1. It replaces the preprocessor kmem flag to gfp flag mapping with
proper translation logic. This eliminates the potential for
surprises that were previously possible where kmem flags were
mapped to gfp flags.
2. It maps vmem_alloc() allocations to kmem_alloc() for allocations
sized less than or equal to the newly-added spl_kmem_alloc_max
parameter. This ensures that small allocations will not contend
on a single global lock, large allocations can still be handled,
and potentially limited virtual address space will not be squandered.
This behavior is entirely different than under Illumos due to
different memory management strategies employed by the respective
kernels. However, this functionally provides the semantics required.
3. The --disable-debug-kmem, --enable-debug-kmem (default), and
--enable-debug-kmem-tracking allocators have been unified in to
a single spl_kmem_alloc_impl() allocation function. This was
done to simplify the code and make it more maintainable.
4. Improve portability by exposing an implementation of the memory
allocations functions that can be safely used in the same way
they are used on Illumos. Specifically, callers may safely
use KM_SLEEP in contexts which perform filesystem IO. This
allows us to eliminate an entire class of Linux specific changes
which were previously required to avoid deadlocking the system.
This change will be largely transparent to existing callers but there
are a few caveats:
1. Because the headers were refactored and extraneous includes removed
callers may find they need to explicitly add additional #includes.
In particular, kmem_cache.h must now be explicitly includes to
access the SPL's kmem cache implementation. This behavior is
different from Illumos but it was done to avoid always masking
the Linux slab functions when kmem.h is included.
2. Callers, like Lustre, which made assumptions about the definitions
of KM_SLEEP, KM_NOSLEEP, and KM_PUSHPAGE will need to be updated.
Other callers such as ZFS which did not will not require changes.
3. KM_PUSHPAGE is no longer overloaded to imply GFP_NOIO. It retains
its original meaning of allowing allocations to access reserved
memory. KM_PUSHPAGE callers can be converted back to KM_SLEEP.
4. The KM_NODEBUG flags has been retired and the default warning
threshold increased to 32k.
5. The kmem_virt() functions has been removed. For callers which
need to distinguish between a physical and virtual address use
is_vmalloc_addr().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Address all cstyle issues in the kmem, vmem, and kmem_cache source
and headers. This will done to make it easier to review subsequent
changes which will rework the kmem/vmem implementation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change introduces no functional changes to the memory management
interfaces. It only restructures the existing codes by separating the
kmem, vmem, and kmem cache implementations in the separate source and
header files.
Splitting this functionality in to separate files required the addition
of spl_vmem_{init,fini}() and spl_kmem_cache_{initi,fini}() functions.
Additionally, several minor changes to the #include's were required to
accommodate the removal of extraneous header from kmem.h.
But again, while large this patch introduces no functional changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
