Hi Jaegeuk, Gu, Changman
> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaeg...@kernel.org]
> Sent: Friday, July 04, 2014 1:36 PM
> To: Gu Zheng
> Cc: f2fs; fsdevel; 이창만; 俞
> Subject: Re: [PATCH 3/4] f2fs: use find_next_bit_le rather than test_bit_le
> in, find_in_block
>
> Well, how about testing with many ones in the bit streams?
> Thanks,
>
> On Thu, Jul 03, 2014 at 06:14:02PM +0800, Gu Zheng wrote:
> > Hi Jaegeuk, Changman
> >
> > Just a simple test, not very sure it can address
> > our qualm.
> >
> > Bitmap size:216(the same as f2fs dentry_bits).
> > CPU: Intel i5 x86_64.
> >
> > Time counting based on tsc(the less the fast).
> > [Index of 1] find_next_bit_le test_bit_le
> > 0 20 117
> > 1 20 114
> > 2 20 113
> > 3 20 139
> > 4 22 121
> > 5 22 118
> > 6 22 115
> > 8 22 112
> > 9 22 106
> > 10 22 105
> > 11 22 100
> > 16 22 98
> > 48 22 97
> > 80 27 95
> > 104 27 92
> > 136 32 95
> > 160 32 92
> > 184 32 90
> > 200 27 87
> > 208 35 84
> >
> > According to the result, find_next_bit_le is always
> > better than test_bit_le, though there may be some
> > noise, but I think the result is clear.
> > Hope it can help us.:)
> > ps.The sample is attached too.
> >
> > Thanks,
> > Gu
I hope this could provide some help for this patch.
I modify Gu's code like this, and add few test case:
static void test_bit_search_speed(void)
{
unsigned long flags;
uint64_t tsc_s_b1, tsc_s_e1, tsc_s_b2, tsc_s_e2;
int i, j, pos;
const void *bit_addr;
local_irq_save(flags);
preempt_disable();
printk("find_next_bit test_bit_le\n");
for (i = 0; i < 24; i++) {
bit_addr = &bitmaps[i];
tsc_s_b1 = rdtsc();
for (j = 0, pos = 0; j < 1000; j++, pos = 0)
while (pos < 216)
pos = find_next_bit_le(bit_addr, 216, pos) + 1;
mb();
tsc_s_e1 = rdtsc();
tsc_s_e1 -= tsc_s_b1;
do_div(tsc_s_e1, 1000);
tsc_s_b2 = rdtsc();
for (j = 0, pos = 0; j < 1000; j++, pos = 0)
while (pos < 216)
test_bit_le(pos++, bit_addr);
mb();
tsc_s_e2 = rdtsc();
tsc_s_e2 -= tsc_s_b2;
do_div(tsc_s_e2, 1000);
printk("%-16llu %-16llu\n", tsc_s_e1, tsc_s_e2);
}
preempt_enable();
local_irq_restore(flags);
}
case: 11111111 11111111
{255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255},
case: 10101010 10101010
{170, 170, 170, 170, 170, 170, 170,
170, 170, 170, 170, 170, 170, 170,
170, 170, 170, 170, 170, 170, 170,
170, 170, 170, 170, 170, 170},
case: 11111111 00000000
{255, 0, 255, 0, 255, 0, 255,
0, 255, 0, 255, 0, 255, 0,
255, 0, 255, 0, 255, 0, 255,
0, 255, 0, 255, 0, 255},
case: 00001111 00001111
{15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15}
and here are test result in my env. (Ubuntu vm, 768MB, i3-3220)
It seems find_next_bit works not so bad as I thought.
find_next_bit test_bit_le
73 4209
62 1271
69 1585
50 2031
67 2255
82 2261
52 4007
79 2159
50 2043
55 2215
53 2393
72 3784
76 1879
61 2562
70 2702
62 2489
56 2307
54 2063
51 2258
69 2712
4133 3989 -- case: 11111111 11111111
2370 3024 -- case: 10101010 10101010
2608 2413 -- case: 11111111 00000000
2457 2506 -- case: 00001111 00001111
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