Andriy Gapon f9cdbaba8d MFV r318946: 8021 ARC buf data scatter-ization ... illumos/illumos-gate@770499e185 770499e185 https://www.illumos.org/issues/8021 The ARC buf data project (known simply as "ABD" since its genesis in the ZoL community) changes the way the ARC allocates `b_pdata` memory from using linear `void *` buffers to using scatter/gather lists of fixed-size 1KB chunks. This improves ZFS's performance by helping to defragment the address space occupied by the ARC, in particular for cases where compressed ARC is enabled. It could also ease future work to allocate pages directly from `segkpm` for minimal- overhead memory allocations, bypassing the `kmem` subsystem. This is essentially the same change as the one which recently landed in ZFS on Linux, although they made some platform-specific changes while adapting this work to their codebase: 1. Implemented the equivalent of the `segkpm` suggestion for future work mentioned above to bypass issues that they've had with the Linux kernel memory allocator. 2. Changed the internal representation of the ABD's scatter/gather list so it could be used to pass I/O directly into Linux block device drivers. (This feature is not available in the illumos block device interface yet.) FreeBSD notes: - the actual (default) chunk size is 4KB (despite the text above saying 1KB) - we can try to reimplement ABDs, so that they are not permanently mapped into the KVA unless explicitly requested, especially on platforms with scarce KVA - we can try to use unmapped I/O and avoid intermediate allocation of a linear, virtual memory mapped buffer - we can try to avoid extra data copying by referring to chunks / pages in the original ABD Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Chris Williamson <chris.williamson@delphix.com> Approved by: Richard Lowe <richlowe@richlowe.net> Author: Dan Kimmel <dan.kimmel@delphix.com> MFC after: 3 weeks		2017-06-20 17:39:24 +00:00
..
zdb_il.c	MFV r318946: 8021 ARC buf data scatter-ization	2017-06-20 17:39:24 +00:00
zdb.8
zdb.c	MFV r318946: 8021 ARC buf data scatter-ization	2017-06-20 17:39:24 +00:00