Kmem rework #2411
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Kmem rework #2411
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I have just refreshed this and openzfs/spl#369 with the changes that I described in #2390 as well as the DMU transaction processing fix that I described on the Open ZFS mailing list. The latter of the two have some trivial merge conflicts with #2484. |
We should have included sys/taskq.h directly because we use the taskq code here, but we instead had files that included sys/taskq.h also include sys/kmem.h, which happened to include sys/taskq.h. sys/kmem.h no longer does this, so we must define the include as we should have done in the first place. Signed-off-by: Richard Yao <ryao@gentoo.org>
We store the bdi in the superblock. This is accessed using virt_to_page in bit_waitqueue(), which does not work on kernel virtual memory. We switch to kzalloc()/kfree() to fix this. Signed-off-by: Richard Yao <ryao@gentoo.org>
It was thought that we could ensure forward progress by avoiding memory allocations during transaction processing and avoiding KM_SLEEP in the few instances in which we could not. Recent tests involving L2ARC on systems without swap have shown that this is not enough. VMWare's bencharmk on a system with 8GB of RAM and 200GB of L2ARC will reliably deadlock when atime is enabled, but will run fine when atime is not enabled. This was initially thought to be a mix of an extreme case of ARC contention and atime updates somehow blocking on transaction group commit, but further examination showed that only 137MB of RAM were in use by L2ARC's headers and additional testing showed no deadlocks occurred with 24GB of RAM when atime was enabled. Subsequent review of the code revealed that the only change was that direct reclaim no longer started transactions to perform atime updates. The logical conclusion is that direct reclaim can occur in locations that hold locks that block an open transaction through some unforeseen dependency chain. This patch attempts to address that by modifying the KM_SLEEP avoidance mechanism to be used in all transaction processing, rather than just operations on zvols. We also take the opportunity to do some cleanup by replacing PF_NOIO with PF_FSTRANS, which is the proper Linux flag for this. Signed-off-by: Richard Yao <ryao@gentoo.org>
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We should have included sys/taskq.h directly because we use the taskq code here, but we instead had files that included sys/taskq.h also include sys/kmem.h, which happened to include sys/taskq.h. sys/kmem.h no longer does this, so we must define the include as we should have done in the first place. Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#2411
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This is a companion for openzfs/spl#369.