From bda9c7d92f24b693eaf0262c090de4c8c108a28e Mon Sep 17 00:00:00 2001 From: David Wang <00107082@163.com> Date: Fri, 8 Nov 2024 13:45:00 +0800 Subject: [PATCH] block/genhd: use seq_put_decimal_ull for diskstats decimal values seq_printf is costly. For each block device, 19 decimal values are yielded in /proc/diskstats via seq_printf. On a system with 16 logical block devices, profiling for open/read/close sequences shows seq_printf took ~75% samples of diskstats_show: diskstats_show(92.626% 2269372/2450040) seq_printf(76.026% 1725313/2269372) vsnprintf(99.163% 1710866/1725313) format_decode(26.597% 455040/1710866) number(19.554% 334542/1710866) memcpy_orig(4.183% 71570/1710866) ... srso_return_thunk(0.009% 148/1725313) part_stat_read_all(8.030% 182236/2269372) One million rounds of open/read/close /proc/diskstats takes: real 0m37.687s user 0m0.264s sys 0m32.911s On average, each sequence tooks ~0.032ms With this patch, most decimal values are yield via seq_put_decimal_ull, performance is significantly improved: real 0m20.792s user 0m0.316s sys 0m20.463s On average, each sequence tooks ~0.020ms, a ~37.5% improvement. Signed-off-by: David Wang <00107082@163.com> Link: https://lore.kernel.org/r/20241108054500.4251-1-00107082@163.com Signed-off-by: Jens Axboe --- block/genhd.c | 63 ++++++++++++++++++++++++--------------------------- 1 file changed, 29 insertions(+), 34 deletions(-) diff --git a/block/genhd.c b/block/genhd.c index 1971c91d6f72..9130e163e191 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1291,40 +1291,35 @@ static int diskstats_show(struct seq_file *seqf, void *v) part_stat_unlock(); } part_stat_read_all(hd, &stat); - seq_printf(seqf, "%4d %7d %pg " - "%lu %lu %lu %u " - "%lu %lu %lu %u " - "%u %u %u " - "%lu %lu %lu %u " - "%lu %u" - "\n", - MAJOR(hd->bd_dev), MINOR(hd->bd_dev), hd, - stat.ios[STAT_READ], - stat.merges[STAT_READ], - stat.sectors[STAT_READ], - (unsigned int)div_u64(stat.nsecs[STAT_READ], - NSEC_PER_MSEC), - stat.ios[STAT_WRITE], - stat.merges[STAT_WRITE], - stat.sectors[STAT_WRITE], - (unsigned int)div_u64(stat.nsecs[STAT_WRITE], - NSEC_PER_MSEC), - inflight, - jiffies_to_msecs(stat.io_ticks), - (unsigned int)div_u64(stat.nsecs[STAT_READ] + - stat.nsecs[STAT_WRITE] + - stat.nsecs[STAT_DISCARD] + - stat.nsecs[STAT_FLUSH], - NSEC_PER_MSEC), - stat.ios[STAT_DISCARD], - stat.merges[STAT_DISCARD], - stat.sectors[STAT_DISCARD], - (unsigned int)div_u64(stat.nsecs[STAT_DISCARD], - NSEC_PER_MSEC), - stat.ios[STAT_FLUSH], - (unsigned int)div_u64(stat.nsecs[STAT_FLUSH], - NSEC_PER_MSEC) - ); + seq_put_decimal_ull_width(seqf, "", MAJOR(hd->bd_dev), 4); + seq_put_decimal_ull_width(seqf, " ", MINOR(hd->bd_dev), 7); + seq_printf(seqf, " %pg", hd); + seq_put_decimal_ull(seqf, " ", stat.ios[STAT_READ]); + seq_put_decimal_ull(seqf, " ", stat.merges[STAT_READ]); + seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_READ]); + seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_READ], + NSEC_PER_MSEC)); + seq_put_decimal_ull(seqf, " ", stat.ios[STAT_WRITE]); + seq_put_decimal_ull(seqf, " ", stat.merges[STAT_WRITE]); + seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_WRITE]); + seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_WRITE], + NSEC_PER_MSEC)); + seq_put_decimal_ull(seqf, " ", inflight); + seq_put_decimal_ull(seqf, " ", jiffies_to_msecs(stat.io_ticks)); + seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_READ] + + stat.nsecs[STAT_WRITE] + + stat.nsecs[STAT_DISCARD] + + stat.nsecs[STAT_FLUSH], + NSEC_PER_MSEC)); + seq_put_decimal_ull(seqf, " ", stat.ios[STAT_DISCARD]); + seq_put_decimal_ull(seqf, " ", stat.merges[STAT_DISCARD]); + seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_DISCARD]); + seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_DISCARD], + NSEC_PER_MSEC)); + seq_put_decimal_ull(seqf, " ", stat.ios[STAT_FLUSH]); + seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_FLUSH], + NSEC_PER_MSEC)); + seq_putc(seqf, '\n'); } rcu_read_unlock();