TRACE_BLOCK_SLEEPRQ(9) Block IO TRACE_BLOCK_SLEEPRQ(9)NAME
trace_block_sleeprq - waiting to get a free request entry in queue for block IO operation
void trace_block_sleeprq(struct request_queue * q, struct bio * bio, int rw);
queue for operation
pending block IO operation
low bit indicates a read (0) or a write (1)
In the case where a request struct cannot be provided for queue q the process needs to wait for an request struct to become available. This
tracepoint event is generated each time the process goes to sleep waiting for request struct become available.
Jason Baron <firstname.lastname@example.org>
William Cohen <email@example.com>
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 TRACE_BLOCK_SLEEPRQ(9)
Check Out this Related Man Page
BLK_MAKE_REQUEST(9) Block Devices BLK_MAKE_REQUEST(9)NAME
blk_make_request - given a bio, allocate a corresponding struct request.
struct request * blk_make_request(struct request_queue * q, struct bio * bio, gfp_t gfp_mask);
target request queue
The bio describing the memory mappings that will be submitted for IO. It may be a chained-bio properly constructed by block/bio layer.
gfp flags to be used for memory allocation
blk_make_request is the parallel of generic_make_request for BLOCK_PC type commands. Where the struct request needs to be farther
initialized by the caller. It is passed a struct bio, which describes the memory info of the I/O transfer.
The caller of blk_make_request must make sure that bi_io_vec are set to describe the memory buffers. That bio_data_dir will return the
needed direction of the request. (And all bio's in the passed bio-chain are properly set accordingly)
If called under none-sleepable conditions, mapped bio buffers must not need bouncing, by calling the appropriate masked or flagged
allocator, suitable for the target device. Otherwise the call to blk_queue_bounce will BUG.
When allocating/cloning a bio-chain, careful consideration should be given to how you allocate bios. In particular, you cannot use
__GFP_WAIT for anything but the first bio in the chain. Otherwise you risk waiting for IO completion of a bio that hasn't been submitted
yet, thus resulting in a deadlock. Alternatively bios should be allocated using bio_kmalloc instead of bio_alloc, as that avoids the
mempool deadlock. If possible a big IO should be split into smaller parts when allocation fails. Partial allocation should not be an error,
or you risk a live-lock.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 BLK_MAKE_REQUEST(9)
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