- 18 Oct, 2021 40 commits
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Christoph Hellwig authored
The polling support in the legacy direct-io support is a little crufty. It already doesn't support the asynchronous polling needed for io_uring polling, and is hard to adopt to upcoming changes in the polling interfaces. Given that all the major file systems already use the iomap direct I/O code, just drop the polling support. Signed-off-by:
Christoph Hellwig <hch@lst.de> Tested-by:
Mark Wunderlich <mark.wunderlich@intel.com> Link: https://lore.kernel.org/r/20211012111226.760968-2-hch@lst.deSigned-off-by:
Jens Axboe <axboe@kernel.dk>
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Jens Axboe authored
Currently we scan the entire plug list, which is potentially very expensive. In an IOPS bound workload, we can drive about 5.6M IOPS with merging enabled, and profiling shows that the plug merge check is the (by far) most expensive thing we're doing: Overhead Command Shared Object Symbol + 20.89% io_uring [kernel.vmlinux] [k] blk_attempt_plug_merge + 4.98% io_uring [kernel.vmlinux] [k] io_submit_sqes + 4.78% io_uring [kernel.vmlinux] [k] blkdev_direct_IO + 4.61% io_uring [kernel.vmlinux] [k] blk_mq_submit_bio Instead of browsing the whole list, just check the previously inserted entry. That is enough for a naive merge check and will catch most cases, and for devices that need full merging, the IO scheduler attached to such devices will do that anyway. The plug merge is meant to be an inexpensive check to avoid getting a request, but if we repeatedly scan the list for every single insert, it is very much not a cheap check. With this patch, the workload instead runs at ~7.0M IOPS, providing a 25% improvement. Disabling merging entirely yields another 5% improvement. Reviewed-by:
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Masahiro Yamada authored
Every object under block/ depends on CONFIG_BLOCK. Move the guard to the top Makefile since there is no point to descend into block/ if CONFIG_BLOCK=n. Signed-off-by:
Masahiro Yamada <masahiroy@kernel.org> Reviewed-by:
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Masahiro Yamada authored
Move the menu to the relevant place. Signed-off-by:
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Masahiro Yamada authored
Everything under block/ depends on BLOCK. BLOCK_HOLDER_DEPRECATED is selected from drivers/md/Kconfig, which is entirely dependent on BLOCK. Extend the 'if BLOCK' ... 'endif' so it covers the whole block/Kconfig. Also, clean up the definition of BLOCK_COMPAT and BLK_MQ_PCI because COMPAT and PCI are boolean. Signed-off-by:
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Masahiro Yamada authored
CONFIG_BLK_CGROUP is a boolean option, that is, its value is 'y' or 'n'. The comparison to 'y' is redundant. Signed-off-by:
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Jens Axboe authored
Add a blk_mq_get_tags() helper, which uses the new sbitmap API for allocating a batch of tags all at once. This both simplifies the block code for batched allocation, and it is also more efficient than just doing repeated calls into __sbitmap_queue_get(). This reduces the sbitmap overhead in peak runs from ~3% to ~1% and yields a performanc increase from 6.6M IOPS to 6.8M IOPS for a single CPU core. Signed-off-by: -
Jens Axboe authored
The block layer tag allocation batching still calls into sbitmap to get each tag, but we can improve on that. Add __sbitmap_queue_get_batch(), which returns a mask of tags all at once, along with an offset for those tags. An example return would be 0xff, where bits 0..7 are set, with tag_offset == 128. The valid tags in this case would be 128..135. A batch is specific to an individual sbitmap_map, hence it cannot be larger than that. The requested number of tags is automatically reduced to the max that can be satisfied with a single map. On failure, 0 is returned. Caller should fall back to single tag allocation at that point/ Signed-off-by: -
Pavel Begunkov authored
We already have a blk_mq_need_time_stamp() check in __blk_mq_end_request() to get a timestamp, hide all the statistics accounting under it. It cuts some cycles for requests that don't need stats, and is free otherwise. Signed-off-by:
Pavel Begunkov <asml.silence@gmail.com> Reviewed-by:
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Christoph Hellwig authored
bio_truncate is only used in bio.c, so mark it static. Signed-off-by:
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Christoph Hellwig authored
bio_get_first_bvec and bio_get_last_bvec are only used in blk-merge.c, so move them there. Signed-off-by:
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Christoph Hellwig authored
Mark __bio_try_merge_page static and move it up a bit to avoid the need for a forward declaration. Signed-off-by:
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Christoph Hellwig authored
bio_full is only used in bio.c, so move it there. Signed-off-by:
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Christoph Hellwig authored
Fold bio_cur_bytes into the only caller. Signed-off-by:
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Christoph Hellwig authored
bio_mergeable is only needed by I/O schedulers, so move it to blk-mq-sched.h. Signed-off-by:
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Christoph Hellwig authored
bio.h doesn't need any of the definitions from ioprio.h. Signed-off-by:
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Christoph Hellwig authored
BIO_DEBUG is always defined, so just switch the two instances to use BUG_ON directly. Signed-off-by:
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Pavel Begunkov authored
Extract a fast check out of __block_mq_sched_restart() and inline it for performance reasons. Signed-off-by:
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Pavel Begunkov authored
Extract hot paths of __blk_account_io_start() and __blk_account_io_done() into inline functions, so we don't always pay for function calls. Signed-off-by:
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Christoph Hellwig authored
Simplify the ioctl path and match the code structure on the compat side. Signed-off-by:
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Christoph Hellwig authored
These are only used inside of block/. Signed-off-by:
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Christoph Hellwig authored
With the raw driver gone, there is no modular user left. Signed-off-by:
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Jens Axboe authored
We could have a race here, where the request gets freed before we call into blk_mq_run_hw_queue(). If this happens, we cannot rely on the state of the request. Grab the hardware context before inserting the flush. Fixes: 0f38d766 ("blk-mq: cleanup blk_mq_submit_bio") Reviewed-by:
Ming Lei <ming.lei@redhat.com> Signed-off-by:
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Christoph Hellwig authored
Move the blk_mq_alloc_data stack allocation only into the branch that actually needs it, and use rq->mq_hctx instead of data.hctx to refer to the hctx. Signed-off-by:
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Christoph Hellwig authored
The newly added loop for the cached requests in __blk_mq_alloc_request is a little too convoluted for my taste, so unwind it a bit. Also rename the function to __blk_mq_alloc_requests now that it can allocate more than a single request. Signed-off-by:
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Jens Axboe authored
The caller typically has a good (or even exact) idea of how many requests it needs to submit. We can make the request/tag allocation a lot more efficient if we just allocate N requests/tags upfront when we queue the first bio from the batch. Provide a new plug start helper that allows the caller to specify how many IOs are expected. This sets plug->nr_ios, and we can use that for smarter request allocation. The plug provides a holding spot for requests, and request allocation will check it before calling into the normal request allocation path. The blk_finish_plug() is called, check if there are unused requests and free them. This should not happen in normal operations. The exception is if we get merging, then we may be left with requests that need freeing when done. This raises the per-core performance on my setup from ~5.8M to ~6.1M IOPS. Signed-off-by: -
Jens Axboe authored
Particularly for NVMe with efficient deferred submission for many requests, there are nice benefits to be seen by bumping the default max plug count from 16 to 32. This is especially true for virtualized setups, where the submit part is more expensive. But can be noticed even on native hardware. Reduce the multiple queue factor from 4 to 2, since we're changing the default size. While changing it, move the defines into the block layer private header. These aren't values that anyone outside of the block layer uses, or should use. Signed-off-by: -
Jens Axboe authored
Doing high IOPS testing with blk-cgroups enabled spends ~15-20% of the time just doing ktime_get_ns() -> readtsc. We essentially read and set the start time twice, one for the bio and then again when that bio is mapped to a request. Given that the time between the two is very short, inherit the bio start time instead of reading it again. This cuts 1/3rd of the overhead of the time keeping. Acked-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
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Jens Axboe authored
Even if no policies are defined, we spend ~2% of the total IO time checking. Move the fast path inline. Acked-by:
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John Garry authored
Now that shared sbitmap support really means shared tags, rename symbols to match that. Signed-off-by:
John Garry <john.garry@huawei.com> Link: https://lore.kernel.org/r/1633429419-228500-15-git-send-email-john.garry@huawei.comSigned-off-by:
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John Garry authored
Now that we use shared tags for shared sbitmap support, we don't require the tags sbitmap pointers, so drop them. This essentially reverts commit 222a5ae0 ("blk-mq: Use pointers for blk_mq_tags bitmap tags"). Function blk_mq_init_bitmap_tags() is removed also, since it would be only a wrappper for blk_mq_init_bitmaps(). Reviewed-by:
Hannes Reinecke <hare@suse.de> Signed-off-by:
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John Garry authored
Currently we use separate sbitmap pairs and active_queues atomic_t for shared sbitmap support. However a full sets of static requests are used per HW queue, which is quite wasteful, considering that the total number of requests usable at any given time across all HW queues is limited by the shared sbitmap depth. As such, it is considerably more memory efficient in the case of shared sbitmap to allocate a set of static rqs per tag set or request queue, and not per HW queue. So replace the sbitmap pairs and active_queues atomic_t with a shared tags per tagset and request queue, which will hold a set of shared static rqs. Since there is now no valid HW queue index to be passed to the blk_mq_ops .init and .exit_request callbacks, pass an invalid index token. This changes the semantics of the APIs, such that the callback would need to validate the HW queue index before using it. Currently no user of shared sbitmap actually uses the HW queue index (as would be expected). Signed-off-by:
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John Garry authored
Refactor blk_mq_free_map_and_requests() such that it can be used at many sites at which the tag map and rqs are freed. Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the alloc equivalent. Suggested-by:
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John Garry authored
Add a function to combine allocating tags and the associated requests, and factor out common patterns to use this new function. Some function only call blk_mq_alloc_map_and_rqs() now, but more functionality will be added later. Also make blk_mq_alloc_rq_map() and blk_mq_alloc_rqs() static since they are only used in blk-mq.c, and finally rename some functions for conciseness and consistency with other function names: - __blk_mq_alloc_map_and_{request -> rqs}() - blk_mq_alloc_{map_and_requests -> set_map_and_rqs}() Suggested-by: -
John Garry authored
Put the functionality to update the sched shared sbitmap size in a common function. Since the same formula is always used to resize, and it can be got from the request queue argument, so just pass the request queue pointer. Signed-off-by:
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John Garry authored
Function blk_mq_clear_rq_mapping() is required to clear the sched tags mappings in driver tags rqs[]. But there is no need for a driver tags to clear its own mapping, so skip clearing the mapping in this scenario. Signed-off-by:
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John Garry authored
Function blk_mq_clear_rq_mapping() will be used for shared sbitmap tags in future, so pass a driver tags pointer instead of the tagset container and HW queue index. Signed-off-by:
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John Garry authored
To be more concise and consistent in naming, rename blk_mq_sched_free_requests() -> blk_mq_sched_free_rqs(). Signed-off-by:
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John Garry authored
Function blk_mq_sched_alloc_tags() does same as __blk_mq_alloc_map_and_request(), so give a similar name to be consistent. Similarly rename label err_free_tags -> err_free_map_and_rqs. Signed-off-by:
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John Garry authored
It's easier to read: if (x) X; else Y; over: if (!x) Y; else X; No functional change intended. Signed-off-by:
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