forked from luck/tmp_suning_uos_patched
3a3947271c
There are a few nits in this function. They could in theory all be separate patches, but that's probably taking small commits too far. 1) I added a brief comment saying what it does. 2) I like to declare pointer parameters "const" where possible for documentation reasons. 3) It uses bitmap_weight(&rand, BITS_PER_LONG) to compute the Hamming weight of a 32-bit random number (giving a random integer with mean 16 and variance 8). Passing by reference in a 64-bit variable is silly; just use hweight32(). 4) Its helper function fract_exp_two is unnecessarily tangled. Gcc can optimize the multiply by (1 << x) to a shift, but it can be written in a much more straightforward way at the cost of one more bit of internal precision. Some analysis reveals that this bit is always available. This shrinks the object code for fract_exp_two(x, 6) from 23 bytes: 0000000000000000 <foo1>: 0: 89 f9 mov %edi,%ecx 2: c1 e9 06 shr $0x6,%ecx 5: b8 01 00 00 00 mov $0x1,%eax a: d3 e0 shl %cl,%eax c: 83 e7 3f and $0x3f,%edi f: d3 e7 shl %cl,%edi 11: c1 ef 06 shr $0x6,%edi 14: 01 f8 add %edi,%eax 16: c3 retq To 19: 0000000000000017 <foo2>: 17: 89 f8 mov %edi,%eax 19: 83 e0 3f and $0x3f,%eax 1c: 83 c0 40 add $0x40,%eax 1f: 89 f9 mov %edi,%ecx 21: c1 e9 06 shr $0x6,%ecx 24: d3 e0 shl %cl,%eax 26: c1 e8 06 shr $0x6,%eax 29: c3 retq (Verified with 0 <= frac_bits <= 8, 0 <= x < 16<<frac_bits; both versions produce the same output.) 5) And finally, the call to bch_get_congested() in check_should_bypass() is separated from the use of the value by multiple tests which could moot the need to compute it. Move the computation down to where it's needed. This also saves a local register to hold the computed value. Signed-off-by: George Spelvin <lkml@sdf.org> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
45 lines
914 B
C
45 lines
914 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHE_REQUEST_H_
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#define _BCACHE_REQUEST_H_
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struct data_insert_op {
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struct closure cl;
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struct cache_set *c;
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struct bio *bio;
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struct workqueue_struct *wq;
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unsigned int inode;
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uint16_t write_point;
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uint16_t write_prio;
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blk_status_t status;
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union {
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uint16_t flags;
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struct {
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unsigned int bypass:1;
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unsigned int writeback:1;
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unsigned int flush_journal:1;
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unsigned int csum:1;
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unsigned int replace:1;
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unsigned int replace_collision:1;
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unsigned int insert_data_done:1;
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};
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};
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struct keylist insert_keys;
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BKEY_PADDED(replace_key);
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};
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unsigned int bch_get_congested(const struct cache_set *c);
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void bch_data_insert(struct closure *cl);
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void bch_cached_dev_request_init(struct cached_dev *dc);
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void bch_flash_dev_request_init(struct bcache_device *d);
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extern struct kmem_cache *bch_search_cache;
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#endif /* _BCACHE_REQUEST_H_ */
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