2 Commits

Author	SHA1	Message	Date
Brian Behlendorf	ff3e2e3c70	Perform KABI checks in parallel ... Reduce the time required for ./configure to perform the needed KABI checks by allowing kbuild to compile multiple test cases in parallel. This was accomplished by splitting each test's source code from the logic handling whether that code could be compiled or not. By introducing this split it's possible to minimize the number of times kbuild needs to be invoked. As importantly, it means all of the tests can be built in parallel. This does require a little extra care since we expect some tests to fail, so the --keep-going (-k) option must be provided otherwise some tests may not get compiled. Furthermore, since a failure during the kbuild modpost phase will result in an early exit; the final linking phase is limited to tests which passed the initial compilation and produced an object file. Once everything has been built the configure script proceeds as previously. The only significant difference is that it now merely needs to test for the existence of a .ko file to determine the result of a given test. This vastly speeds up the entire process. New test cases should use ZFS_LINUX_TEST_SRC to declare their test source code and ZFS_LINUX_TEST_RESULT to check the result. All of the existing kernel-*.m4 files have been updated accordingly, see config/kernel-current-time.m4 for a basic example. The legacy ZFS_LINUX_TRY_COMPILE macro has been kept to handle special cases but it's use is not encouraged. master (secs) patched (secs) ------------- ---------------- autogen.sh 61 68 configure 137 24 (~17% of current run time) make -j $(nproc) 44 44 make rpms 287 150 Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8547 Closes #9132 Closes #9341 Conflicts: Makefile.am config/kernel-fpu.m4	2020-01-22 13:49:01 -08:00
Brian Behlendorf	a584ef2605	Direct IO support ... Direct IO via the O_DIRECT flag was originally introduced in XFS by IRIX for database workloads. Its purpose was to allow the database to bypass the page and buffer caches to prevent unnecessary IO operations (e.g. readahead) while preventing contention for system memory between the database and kernel caches. On Illumos, there is a library function called directio(3C) that allows user space to provide a hint to the file system that Direct IO is useful, but the file system is free to ignore it. The semantics are also entirely a file system decision. Those that do not implement it return ENOTTY. Since the semantics were never defined in any standard, O_DIRECT is implemented such that it conforms to the behavior described in the Linux open(2) man page as follows. 1. Minimize cache effects of the I/O. By design the ARC is already scan-resistant which helps mitigate the need for special O_DIRECT handling. Data which is only accessed once will be the first to be evicted from the cache. This behavior is in consistent with Illumos and FreeBSD. Future performance work may wish to investigate the benefits of immediately evicting data from the cache which has been read or written with the O_DIRECT flag. Functionally this behavior is very similar to applying the 'primarycache=metadata' property per open file. 2. O_DIRECT _MAY_ impose restrictions on IO alignment and length. No additional alignment or length restrictions are imposed. 3. O_DIRECT _MAY_ perform unbuffered IO operations directly between user memory and block device. No unbuffered IO operations are currently supported. In order to support features such as transparent compression, encryption, and checksumming a copy must be made to transform the data. 4. O_DIRECT _MAY_ imply O_DSYNC (XFS). O_DIRECT does not imply O_DSYNC for ZFS. Callers must provide O_DSYNC to request synchronous semantics. 5. O_DIRECT _MAY_ disable file locking that serializes IO operations. Applications should avoid mixing O_DIRECT and normal IO or mmap(2) IO to the same file. This is particularly true for overlapping regions. All I/O in ZFS is locked for correctness and this locking is not disabled by O_DIRECT. However, concurrently mixing O_DIRECT, mmap(2), and normal I/O on the same file is not recommended. This change is implemented by layering the aops->direct_IO operations on the existing AIO operations. Code already existed in ZFS on Linux for bypassing the page cache when O_DIRECT is specified. References: * http://xfs.org/docs/xfsdocs-xml-dev/XFS_User_Guide/tmp/en-US/html/ch02s09.html * https://blogs.oracle.com/roch/entry/zfs_and_directio * https://ext4.wiki.kernel.org/index.php/Clarifying_Direct_IO's_Semantics * https://illumos.org/man/3c/directio Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #224 Closes #7823	2018-08-27 10:04:21 -07:00