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Josh Paetzel 1e37d7e555 6569 large file delete can starve out write ops ... illumos/illumos-gate@ff5177ee8b ff5177ee8b https://www.illumos.org/issues/6569 The core issue I've found is that there is no throttle for how many deletes get assigned to one TXG. As a results when deleting large files we end up filling consecutive TXGs with deletes/frees, then write throttling other (more important) ops. There is an easy test case for this problem. Try deleting several large files (at least 1/2 TB) while you do write ops on the same pool. What we've seen is performance of these write ops (let's call it sideload I/O) would drop to zero. More specifically the problem is that dmu_free_long_range_impl() can/will fill up all of the dirty data in the pool "instantly", before many of the sideload ops can get in. So sideload performance will be impacted until all the files are freed. The solution we have tested at Nexenta (with positive results) creates a relatively simple throttle for how many "free" ops we let into one TXG. However this solution exposes other problems that should also be addressed. If we are to slow down freeing of data that means one has to wait even longer (assuming vnode ref count of 1) to get shell back after an rm or for NFS thread to finish the free-ing op. To avoid this the proposed solution is to call zfs_inactive() async for "large" files. Async freeing then begs for the reclaimed space to be accounted for in the zpool's "freeing" prop. The other issue with having a longer delete is the inability to export/unmount for a longer period of time. The proposed solution is to interrupt freeing of blocks when a fs is unmounted. Author: Alek Pinchuk <alek@nexenta.com> Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com>		2017-01-19 20:44:29 +00:00
cmd	7297 clear() on llquantize aggregation causes dtrace to exit	2016-08-26 20:51:09 +00:00
common	5778 nvpair_type_is_array() does not recognize DATA_TYPE_INT8_ARRAY	2016-11-02 17:34:33 +00:00
head	5066 remove support for non-ANSI compilation	2014-08-20 06:29:42 +00:00
lib	6428 set canmount=off on unmounted filesystem tries to unmount children	2016-11-22 11:50:52 +00:00
man	7277 zdb should be able to print zfs_dbgmsg's	2016-08-15 14:24:47 +00:00
tools/ctf	5589 improper use of NULL in tools/ctf	2015-03-09 20:43:14 +00:00
uts	6569 large file delete can starve out write ops	2017-01-19 20:44:29 +00:00
OPENSOLARIS.LICENSE	Update vendor/opensolaris to last OpenSolaris state (13149:b23a4dab3d50)	2012-07-18 07:48:04 +00:00