Hi Jaegeuk, Gu, Changman > -----Original Message----- > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx] > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
