Add the initial support for the 'smbshare' option using the
existing libshare infrastructure. Because this implementation
relies on usershares samba version 3.0.23 is required.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#493
Commit df83110856 missed update to
getopt() call, while delivering all the rest. This commit adds
"o" to getopt().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #566
Add the missing error handling to load_nvlist(). There's no good
reason this needs to be fatal. All callers of load_nvlist() do
correctly handle an error condition and it is preferable that an
error be returned. This will allow 'zpool import -FX' to safely
attempt to rollback through previous txgs looking for a good one.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1120
Commit 57a4edd allows the bootfs property to be set on any pool.
However, many of the zpool commands still prevent you from using
EFI labeled devices for the root pool. For example:
# zpool attach rpool /dev/sda /dev/sdb
cannot label 'sdb': EFI labeled devices are not supported on
root pools. on root devices.
For non-Solaris builds such as Linux disable this error.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1077
Due to the slightly increased size of the ZFS super block
caused by 30315d2 there are now allocation warnings. The
allocation size is still small (just over 8k) and super
blocks are rarely allocated so we suppress the warning.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1101
Previously this check was only performed when ./configure was
attempting to autodetect your kernel source directory. But we
should also handle the case where --with-linux was provided
and is obviously wrong. This way we catch the error before
invoking make and compiling the source with an incorrect
autoconf results.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/spl#162
While expanding positional parameters shell requires non-single
digits to be enclosed in braces. When the SAS topology is
non-trivial the number of positional parameters generated internally
by vdev_id script (using set -- ...) easily crosses single digit limit
and vdev_id fails to generate links.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1119
Full bash may not be available in all environments where udev helpers
run, such as in an initial ramdisk. To avoid breakage in this case,
remove use of bash-specific features such as variable arrays and the
`declare' keyword from the vdev_id script.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#870
If zvol_alloc() fails zv will be set to NULL and dereferenced
in out_dmu_objset_disown. To avoid this entirely the zv->objset
line is moved up in to the success block.
Original-patch-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1109
Increasing this limit costs us 6144 bytes of memory per mounted
filesystem, but this is small price to pay for accomplishing
the following:
* Allows for up to 256-way concurreny when performing lookups
which helps performance when there are a large number of
processes.
* Minimizes the likelyhood of encountering the deadlock
described in issue #1101. Because vmalloc() won't strictly
honor __GFP_FS there is still a very remote chance of a
deadlock. See the zfsonlinux/spl@043f9b57 commit.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1101
When a zvol with snapshots is renamed the device files under
/dev/zvol/ are not renamed. This patch resolves the problem
by destroying and recreating the minors with the new name so
the links can be recreated bu udev.
Original-patch-by: Suman Chakravartula <schakrava@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#408
Canonicalize the mount point passed to the mount.zfs helper.
This way a clean path is always added to mtab which ensures
the umount can properly locate and remove the entry.
Test case:
$ mkdir /mnt/foo
$ mount -t zfs zpool/foo /mnt/../mnt/foo////
$ umount /mnt/foo
$ cat /etc/mtab | grep zpool/foo
zpool/foo /mnt/../mnt/foo//// zfs rw 0 0
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#573
This branch adds some overdue ashift improvements.
* Add '-o ashift' to 'zpool add' and 'zpool attach'
* Improve AF hard disk detection
* Allow 'zpool import' to handle increases in ashift
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When adding devices to an existing pool "ashift" property is
auto-detected. However, if this property was overridden at
the pool creation time (i.e. zpool create -o ashift=12 tank ...)
this may not be what the user wants. This commit lets the user
specify the value of "ashift" property to be used with newly
added drives. For example,
zpool add -o ashift=12 tank disk1
zpool attach -o ashift=12 tank disk1 disk2
Signed-off-by: Cyril Plisko <cyril.plisko@mountall.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#566
Use the bdev_physical_block_size() interface to determine the
minimize write size which can be issued without incurring a
read-modify-write operation. This is used to set the ashift
correctly to prevent a performance penalty when using AF hard
disks.
Unfortunately, this interface isn't entirely reliable because
it's not uncommon for disks to misreport this value. For this
reason you may still need to manually set your ashift with:
zpool create -o ashift=12 ...
The solution to this in the upstream Illumos source was to add
a white list of known offending drives. Maintaining such a list
will be a burden, but it still may be worth doing if we can
detect a large number of these drives. This should be considered
as future work.
Reported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#916
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Richard Elling <richard.elling@richardelling.com>
Reviewed by: Gordon Ross <gwr@nexenta.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Richard Lowe <richlowe@richlowe.net>
Refererces to Illumos issue:
https://www.illumos.org/issues/2671
This patch has been slightly modified from the upstream Illumos
version. In the upstream implementation a warning message is
logged to the console. To prevent pointless console noise this
notification is now posted as a "ereport.fs.zfs.vdev.bad_ashift"
event.
The event indicates a non-optimial (but entirely safe) ashift
value was used to create the pool. Depending on your workload
this may impact pool performance. Unfortunately, the only way
to correct the issue is to recreate the pool with a new ashift.
NOTE: The unrelated fix to the comment in zpool_main.c appears
in the upstream commit and was preserved for consistnecy.
Ported-by: Cyril Plisko <cyril.plisko@mountall.com>
Reworked-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#955
The udev data directory was hard coded in 60-vdev.rules.in. That causes
a problem when a distribution changes the location of the directory.
This was not an issue in the past because virtually all distributions
used the same path, but that is beginning to change following a decision
by the systemd developers to change the directory location to reflect
their take-over of udev maintainership. The testing branch of Gentoo
Linux adopted this change, which enabled the hardcoded directory
location to trigger a regression.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1085
Gunnar Beutner did all the hard work on this one by correctly
identifying that this issue is a race between dmu_sync() and
dbuf_dirty().
Now in all cases the caller is responsible for preventing this
race by making sure the zfs_range_lock() is held when dirtying
a buffer which may be referenced in a log record. The mmap
case which relies on zfs_putpage() was not taking the range
lock. This code was accidentally dropped when the function
was rewritten for the Linux VFS.
This patch adds the required range locking to zfs_putpage().
It also adds the missing ZFS_ENTER()/ZFS_EXIT() macros which
aren't strictly required due to the VFS holding a reference.
However, this makes the code more consistent with the upsteam
code and there's no harm in being extra careful here.
Original-patch-by: Gunnar Beutner <gunnar@beutner.name>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#541
When using a zvol to back a btrfs filesystem the btrfs mount
would hang. This was due to the bio completion callback used
in btrfs assuming that lower level drivers would never modify
the bio->bi_io_vecs after they were submitted via bio_submit().
If they are modified btrfs will miscalculate which pages need
to be unlocked resulting in a hang.
It's worth mentioning that other file systems such as ext[234]
and xfs work fine because they do not make the same assumption
in the bio completion callback.
The most straight forward way to fix the issue is to present
the semantics expected by btrfs. This is done by cloning the
bios attached to each request and then using the clones bvecs
to perform the required accounting. The clones are freed after
each read/write and the original unmodified bios are linked back
in to the request.
Signed-off-by: Chris Wedgwood <cw@f00f.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#469
Bring in support for the new KSTAT_TYPE_TXG type. This allows for
additional visibility in to the txg handling.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
There have been reports of ZFS deadlocking due to what appears to
be a lost IO. This patch addes some debugging to determine the
exact state of the IO which neither 1) completed, 2) failed, or
3) timed out after zio_delay_max (30) seconds.
This information will be logged using the ZFS FMA infrastructure
as a 'delay' event and posted to the internal zevent log. By
default the last 64 events will be kept in the log but the limit
is configurable via the zfs_zevent_len_max module option.
To dump the contents of the log use the 'zpool events -v' command
and look for the resource.fs.zfs.delay event. It will include
various information about the pool, vdev, and zio which may shed
some light on the issue.
In the context of this change the 120 second kernel blocked thread
watchdog has been disabled for synchronous IOs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #930
Create a kstat file which contains useful statistics about the
last N txgs processed. This can be helpful when analyzing pool
performance. The new KSTAT_TYPE_TXG type was added for this
purpose and it tracks the following statistics per-txg.
txg - Unique txg number
state - State (O)pen/(Q)uiescing/(S)yncing/(C)ommitted
birth; - Creation time
nread - Bytes read
nwritten; - Bytes written
reads - IOPs read
writes - IOPs write
open_time; - Length in nanoseconds the txg was open
quiesce_time - Length in nanoseconds the txg was quiescing
sync_time; - Length in nanoseconds the txg was syncing
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The interface for the ddt_zap_count() function assumes it can
never fail. However, internally ddt_zap_count() is implemented
with zap_count() which can potentially fail. Now because there
was no way to return the error to the caller a VERIFY was used
to ensure this case never happens.
Unfortunately, it has been observed that pools can be damaged in
such a way that zap_count() fails. The result is that the pool can
not be imported without hitting the VERIFY and crashing the system.
This patch reworks ddt_object_count() so the error can be safely
caught and returned to the caller. This allows a pool which has
be damaged in this way to be safely rewound for import.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#910
This reverts commit a5c20e2a0a which
accidentally introduced a regression for real 4k sector devices.
See issue #1065 for details.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1065
The following warning was originally added to provide visibility
in to how often a dio gets heavily fragmented in to over 16 bios.
This can happen due to constraints imposed by the block device
and may have a negitive impact on performance but is otherwise
harmless. To prevent needless confusion and worry the message
has been removed.
kernel: WARNING: Resized bio's/dio to 32
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
During 'zpool import' all ZPOOL_CONFIG_PATH names are supposed
to be updated by fix_paths(). This was not happening for spare
and cache devices because the proper names were getting filtered
out of the pool_list_t->names. Interestingly, the names were
being filtered because the spare and cache devices do not
contain the pool name in their vdev label.
The fix is to exclude the device path from the list only if:
1) has a valid ZPOOL_CONFIG_POOL_NAME key in the label, and
2) that pool name does not match the specified pool name.
Since the label is valid and because it does properly store the
vdev guid it will be correctly assembled without the pool name.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#725
The 'zpool replace' command would fail when given a short name
because unlike on other platforms the short name cannot be
deterministically expanded to a single path. Multiple path
prefixes must be checked and in addition the partition suffix
for whole disks is determined by the prefix.
To handle this complexity a zfs_strcmp_pathname() function was
added which takes either a short or fully qualified device name.
Short names will be expanded using the prefixes in the default
import search path, or the ZPOOL_IMPORT_PATH environment variable
if it's defined. All posible expansions are then compared against
the comparison path. Care is taken to strip redundant slashes to
ensure legitimate matches are not missed.
In the context of this work the existing zfs_resolve_shortname()
function was extended to consider the ZPOOL_IMPORT_PATH when set.
The zfs_append_partition() interface was also simplified to take
only a single buffer.
The vast majority of these changes rework existing Linux specific
code which was originally written to accomidate udev. However,
there is some minimal cleanup which removes Illumos specific code.
This was done to improve readability but the basic flow and intent
of the upstream code was maintained.
These changes are the logical conclusion of the previos work to
adjust the 'zpool import' search behavior, see commit 44867b6a.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#544Closes#976
When automounting a snapshot in the .zfs/snapshot directory
make sure to quote both the dataset name and the mount point.
This ensures that if either component contains spaces, which
are allowed, they get handled correctly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1027
This brnach brings some ZIL performance optimizations, with
significant increases in synchronous write performance for
some workloads and pool configurations.
See the individual commit messages for details.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1013
In the current code, logbias=throughput implies the following:
1) All synchronous writes are logged in indirect mode.
2) The slog is not used.
(1) makes sense because it avoids writing the data twice, which is
obviously a good thing when the user wants maximum pool throughput.
(2), however, is a surprising decision. Considering all writes are
indirect, the log record doesn't contain the actual data, only pointers
to DMU blocks. As a result, log records written in logbias=throughput
mode are quite small, and as such, it doesn't make any sense to write
them to the main pool since slogs are usually optimized for small
synchronous writes.
In fact, the current behavior is actually harmful for performance,
because log blocks and data blocks from dmu_sync() seldom have the same
allocation size and as a result are usually allocated from different
metaslabs. This means that if a spindle has to write both log blocks and
DMU blocks (which is likely to happen under heavy load), it will have to
seek between the two. Allocating the log blocks from the slog pool
instead of the main pool avoids these unnecessary seeks.
This commit makes ZFS use the slog on datasets with logbias=throughput.
Real-life performance testing shows a 50% synchronous write performance
increase with some large commit sizes, and no negative effect in other
cases.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1013
Currently, ZIL blocks are spread over vdevs using hint block pointers
managed by the ZIL commit code and passed to metaslab_alloc(). Spreading
log blocks accross vdevs is important for performance: indeed, using
mutliple disks in parallel decreases the ZIL commit latency, which is
the main performance metric for synchronous writes. However, the current
implementation suffers from the following issues:
1) It would be best if the ZIL module was not aware of such low-level
details. They should be handled by the ZIO and metaslab modules;
2) Because the hint block pointer is managed per log, simultaneous
commits from multiple logs might use the same vdevs at the same time,
which is inefficient;
3) Because dmu_write() does not honor the block pointer hint, indirect
writes are not spread.
The naive solution of rotating the metaslab rotor each time a block is
allocated for the ZIL or dmu_sync() doesn't work in practice because the
first ZIL block to be written is actually allocated during the previous
commit. Consequently, when metaslab_alloc() decides the vdev for this
block, it will do so while a bunch of other allocations are happening at
the same time (from dmu_sync() and other ZILs). This means the vdev for
this block is chosen more or less at random. When the next commit
happens, there is a high chance (especially when the number of blocks
per commit is slightly less than the number of the disks) that one disk
will have to write two blocks (with a potential seek) while other disks
are sitting idle, which defeats spreading and increases the commit
latency.
This commit introduces a new concept in the metaslab allocator:
fastwrites. Basically, each top-level vdev maintains a counter
indicating the number of synchronous writes (from dmu_sync() and the
ZIL) which have been allocated but not yet completed. When the metaslab
is called with the FASTWRITE flag, it will choose the vdev with the
least amount of pending synchronous writes. If there are multiple vdevs
with the same value, the first matching vdev (starting from the rotor)
is used. Once metaslab_alloc() has decided which vdev the block is
allocated to, it updates the fastwrite counter for this vdev.
The rationale goes like this: when an allocation is done with
FASTWRITE, it "reserves" the vdev until the data is written. Until then,
all future allocations will naturally avoid this vdev, even after a full
rotation of the rotor. As a result, pending synchronous writes at a
given point in time will be nicely spread over all vdevs. This contrasts
with the previous algorithm, which is based on the implicit assumption
that blocks are written instantaneously after they're allocated.
metaslab_fastwrite_mark() and metaslab_fastwrite_unmark() are used to
manually increase or decrease fastwrite counters, respectively. They
should be used with caution, as there is no per-BP tracking of fastwrite
information, so leaks and "double-unmarks" are possible. There is,
however, an assert in the vdev teardown code which will fire if the
fastwrite counters are not zero when the pool is exported or the vdev
removed. Note that as stated above, marking is also done implictly by
metaslab_alloc().
ZIO also got a new FASTWRITE flag; when it is used, ZIO will pass it to
the metaslab when allocating (assuming ZIO does the allocation, which is
only true in the case of dmu_sync). This flag will also trigger an
unmark when zio_done() fires.
A side-effect of the new algorithm is that when a ZIL stops being used,
its last block can stay in the pending state (allocated but not yet
written) for a long time, polluting the fastwrite counters. To avoid
that, I've implemented a somewhat crude but working solution which
unmarks these pending blocks in zil_sync(), thus guaranteeing that
linguering fastwrites will get pruned at each sync event.
The best performance improvements are observed with pools using a large
number of top-level vdevs and heavy synchronous write workflows
(especially indirect writes and concurrent writes from multiple ZILs).
Real-life testing shows a 200% to 300% performance increase with
indirect writes and various commit sizes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1013
Both the SPL and the ZFS libspl export most of the atomic_* functions,
except atomic_sub_* functions which are only exported by the SPL, not by
libspl. This patch remedies that by implementing atomic_sub_* functions
in libspl.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1013
Auditing the code to verify that all instances of cv_signal() and
cv_broadcast() are called under the proper associated mutex turned
up several races. None of these have been conclusively seen in the
wild but the following patch set resolves them.
For reference, from the cv_signal(9F) man page:
cv_signal() signals the condition and wakes one blocked thread.
All blocked threads can be unblocked by calling cv_broadcast().
You must acquire the mutex passed into cv_wait() before calling
cv_signal() or cv_broadcast()
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1048
The following incorrect usage of cv_broadcast() was caught by
code inspection. The cv_broadcast() function must be called
under the associated mutex to preventing racing with cv_wait().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The following incorrect usage of cv_signal and cv_broadcast()
was caught by code inspection. The cv_signal and cv_broadcast()
functions must be called under the associated mutex to preventing
racing with cv_wait().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The following incorrect usage of cv_broadcast() was caught by
code inspection. The cv_broadcast() function must be called
under the associated mutex to preventing racing with cv_wait().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The function unused_loop_device in /usr/libexec/zfs/common.sh
returns /dev/loop-control on the first call. This device is NOT
a loop device (https://github.com/torvalds/linux/commit/770fe30)
it is a control device. This in turn causes the script zconfig.sh
to fail with:
zpool-create.sh: Error 1 creating /tmp/zpool-vdev0 ->
/dev/loop-control loopback
The patch makes the function return /dev/loop[0-9]* which are
loop devices.
Signed-off-by: Andrew Reid <ColdCanuck@nailedtotheperch.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#797
In this particular instance the allocation occurred in the context
of sys_msync()->...->zpl_putpage() where we must be careful not to
initiate additional I/O.
Signed-off-by: Massimo Maggi <massimo@mmmm.it>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1038
Prevent users from setting the zfs_vdev_aggregation_limit tuning
larger than SPA_MAXBLOCKSIZE.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#520
Otherwise it will cause zpl_shares_lookup() to return a invalid
pointer when an error occurs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Closes#626#885#947#977
The ztest deadman timer has been causing false positives in the
testing VMs. To make it easier to spot possible regressions
I'm disabling this timer. The buildbot test infrastructure
will still mark ztest instances which take to long to complete
as failures.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1018
Use .mkdir instead of .create in 3.3 compatibility check. Linux 3.6
modifies inode_operations->create's function prototype. This causes
an autotools Linux 3.3. compatibility check for a function prototype
change in create, mkdir and mknode to fail. Since mkdir and mknode
are unchanged, we modify the check to examine it instead.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #873
As of Linux commit ebfc3b49a7ac25920cb5be5445f602e51d2ea559 the
struct nameidata is no longer passed to iops->create. Instead
only the result of (inamedata->flags & LOOKUP_EXCL) is passed.
ZFS like almost all Linux fileystems never made use of this so
only the prototype needs to be wrapped for compatibility.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #873
As of Linux commit 00cd8dd3bf95f2cc8435b4cac01d9995635c6d0b the
struct nameidata is no longer passed to iops->lookup. Instead
only the inamedata->flags are passed.
ZFS like almost all Linux fileystems never made use of this so
only the prototype needs to be wrapped for compatibility.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #873
As of Linux commit 9249e17fe094d853d1ef7475dd559a2cc7e23d42 the
mount flags are now passed to sget() so they can be used when
initializing a new superblock.
ZFS never uses sget() in this fashion so we can simply pass a
zero and add a zpl_sget() compatibility wrapper.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #873
The .write_super callback was removed the the super_operations
structure by Linux commit f0cd2dbb6cf387c11f87265462e370bb5469299e.
All file systems are now expected to self manage writing any dirty
state assoicated with their super block.
ZFS never made use of this callback so it can simply be removed
from the super_operations structure.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #873
Currently, the size of read and write requests on vdevs is aligned
according to the vdev's ashift, allocating a new ZIO buffer and padding
if need be.
This makes sense for write requests to prevent read/modify/write if the
write happens to be smaller than the device's internal block size.
For reads however, the rationale is less clear. It seems that the
original code aligns reads because, on Solaris, device drivers will
outright refuse unaligned requests.
We don't have that issue on Linux. Indeed, Linux block devices are able
to accept requests of any size, and take care of alignment issues
themselves.
As a result, there's no point in enforcing alignment for read requests
on Linux. This is a nice optimization opportunity for two reasons:
- We remove a memory allocation in a heavily-used code path;
- The request gets aligned in the lowest layer possible, which shrinks
the path that the additional, useless padding data has to travel.
For example, when using 4k-sector drives that lie about their sector
size, using 512b read requests instead of 4k means that there will
be less data traveling down the ATA/SCSI interface, even though the
drive actually reads 4k from the platter.
The only exception is raidz, because raidz needs to read the whole
allocated block for parity.
This patch removes alignment enforcement for read requests, except on
raidz. Note that we also remove an assertion that checks that we're
aligning a top-level vdev I/O, because that's not the case anymore for
repair writes that results from failed reads.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1022
There are currently three vmem_size() consumers all of which are
part of the ARC implemention. However, since the expected behavior
of the Linux and Solaris virtual memory subsystems are so different
the behavior in each of these instances needs to be reevaluated.
* arc_evict_needed() - This is actually dead code. Arena support
was never added to the SPL and zio_arena is always NULL. This
support isn't needed so we simply remove this dead code.
* arc_memory_throttle() - On Solaris where virtual memory constitutes
almost all of the address space we can reasonably expect there to be
a fairly large amount free. However, on Linux by default we only
have about 100MB total and that's heavily used by the ARC. So the
expectation on Linux is that this will usually be a small value.
Therefore we remove the vmem_size() check for i386 systems because
the expectation is that it will be less than the zfs_write_limit_max.
* arc_init() - Here vmem_size() is used to initially size the ARC.
Since the ARC is currently backed by the virtual address space it
makes sense to use this as a limit on the ARC for 32-bit systems.
This code can be removed when the ARC is backed by the page cache.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#831
