Messages in this thread Patch in this message | | | Date | Sat, 29 Oct 2005 14:02:28 +0800 | From | Wu Fengguang <> | Subject | [PATCH 12/13] readahead: events accounting |
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A debugfs file named `readahead' is created according to advices from J?rn Engel, Andrew Morton and Ingo Oeser. It yields to much better readability than the preious /proc/vmstat interface :)
It reveals various read-ahead activities/events, and is vital to the testing.
This is a trimmed down output on my PC: # cat /debugfs/readahead [table requests] total newfile state context contexta cache_miss 234 50 10 54 0 read_random 116 37 4 21 0 io_congestion 0 0 0 0 0 io_cache_hit 61 0 14 37 0 io_block 4994 1576 232 120 2 readahead 1812 1522 171 107 2 lookahead 596 442 76 78 0 lookahead_hit 214 89 70 32 1 readahead_eof 1208 1080 95 21 2 readahead_shrink 0 0 0 0 0 readahead_thrash 0 0 0 0 0 readahead_rescue 1275 0 0 0 0
[table pages] total newfile state context contexta cache_miss 401 98 50 87 0 read_random 120 37 4 21 0 io_congestion 0 0 0 0 0 io_cache_hit 872 0 412 448 0 io_block 22833 3857 12177 3680 21 readahead 15081 3827 9683 1484 21 readahead_hit 12684 3441 8164 1001 22 lookahead 8191 936 6926 329 0 lookahead_hit 8140 230 6368 1542 0 readahead_eof 5192 1955 2777 373 21 readahead_shrink 0 0 0 0 0 readahead_thrash 0 0 0 0 0 readahead_rescue 13656 0 0 0 0
[table summary] total newfile state context contexta random_rate 6% 2% 2% 16% 0% ra_hit_rate 84% 89% 84% 67% 100% la_hit_rate 35% 20% 90% 40% 100% avg_ra_size 8 3 56 14 7 avg_la_size 14 2 90 4 0
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> ---
mm/readahead.c | 194 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 192 insertions(+), 2 deletions(-)
--- linux-2.6.14-rc5-mm1.orig/mm/readahead.c +++ linux-2.6.14-rc5-mm1/mm/readahead.c @@ -47,6 +47,9 @@ enum ra_class { enum ra_event { RA_EVENT_CACHE_MISS, /* read cache misses */ RA_EVENT_READRANDOM, /* random reads */ + RA_EVENT_IO_CONGESTION, /* io congestion */ + RA_EVENT_IO_CACHE_HIT, /* canceled io due to cache hit */ + RA_EVENT_IO_BLOCK, /* read on locked page */ RA_EVENT_READAHEAD, /* read-ahead issued */ RA_EVENT_READAHEAD_HIT, /* read-ahead page hit */ @@ -65,6 +68,177 @@ enum ra_event { */ #define DEBUG_READAHEAD #ifdef DEBUG_READAHEAD +#include <linux/jiffies.h> +#include <linux/debugfs.h> +#include <linux/seq_file.h> +#include <linux/init.h> + +static char *ra_class_name[] = { + "total", + "newfile", + "state", + "context", + "contexta", + "backward", + "onthrash", + "onraseek", + "none", +}; + +static char *ra_event_name[] = { + "cache_miss", + "read_random", + "io_congestion", + "io_cache_hit", + "io_block", + "readahead", + "readahead_hit", + "lookahead", + "lookahead_hit", + "readahead_eof", + "readahead_shrink", + "readahead_thrash", + "readahead_rescue", +}; + +static unsigned long ra_event_count[RA_CLASS_END+1][RA_EVENT_END][2]; + +static inline void ra_account(struct file_ra_state *ra, + enum ra_event e, int pages) +{ + enum ra_class c; + + c = (ra ? ra->flags & RA_CLASS_MASK : RA_CLASS_END); + if (e == RA_EVENT_READAHEAD_HIT && pages < 0) { + c = (ra->flags >> RA_CLASS_SHIFT) & RA_CLASS_MASK; + pages = -pages; + } + if (!c) + c = RA_CLASS_END; + BUG_ON(c > RA_CLASS_END); + + ra_event_count[c][e][0] += 1; + ra_event_count[c][e][1] += pages; +} + +static int ra_account_show(struct seq_file *s, void *_) +{ + int i; + int c; + int e; + static char event_fmt[] = "%-16s"; + static char class_fmt[] = "%11s"; + static char item_fmt[] = "%11lu"; + static char percent_format[] = "%10lu%%"; + static char *table_name[] = { + "[table requests]", + "[table pages]", + "[table summary]"}; + + for (i = 0; i <= 1; i++) { + for (e = 0; e < RA_EVENT_END; e++) { + ra_event_count[0][e][i] = 0; + for (c = 1; c <= RA_CLASS_END; c++) + ra_event_count[0][e][i] += + ra_event_count[c][e][i]; + } + + seq_printf(s, event_fmt, table_name[i]); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, class_fmt, ra_class_name[c]); + seq_puts(s, "\n"); + + for (e = 0; e < RA_EVENT_END; e++) { + if (e == RA_EVENT_READAHEAD_HIT && i == 0) + continue; + + seq_printf(s, event_fmt, ra_event_name[e]); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, item_fmt, + ra_event_count[c][e][i]); + seq_puts(s, "\n"); + } + seq_puts(s, "\n"); + } + + seq_printf(s, event_fmt, table_name[2]); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, class_fmt, ra_class_name[c]); + seq_puts(s, "\n"); + + seq_printf(s, event_fmt, "random_rate"); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, percent_format, + (ra_event_count[c][RA_EVENT_READRANDOM][0] * 100) / + (ra_event_count[c][RA_EVENT_READRANDOM][0] + + ra_event_count[c][RA_EVENT_READAHEAD][0] + 1)); + seq_puts(s, "\n"); + + seq_printf(s, event_fmt, "ra_hit_rate"); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, percent_format, + (ra_event_count[c][RA_EVENT_READAHEAD_HIT][1] * 100) / + (ra_event_count[c][RA_EVENT_READAHEAD][1] + 1)); + seq_puts(s, "\n"); + + seq_printf(s, event_fmt, "la_hit_rate"); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, percent_format, + (ra_event_count[c][RA_EVENT_LOOKAHEAD_HIT][0] * 100) / + (ra_event_count[c][RA_EVENT_LOOKAHEAD][0] + 1)); + seq_puts(s, "\n"); + + seq_printf(s, event_fmt, "avg_ra_size"); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, item_fmt, + (ra_event_count[c][RA_EVENT_READAHEAD][1] + + ra_event_count[c][RA_EVENT_READAHEAD][0] / 2) / + (ra_event_count[c][RA_EVENT_READAHEAD][0] + 1)); + seq_puts(s, "\n"); + + seq_printf(s, event_fmt, "avg_la_size"); + for (c = 0; c <= RA_CLASS_END; c++) + seq_printf(s, item_fmt, + (ra_event_count[c][RA_EVENT_LOOKAHEAD][1] + + ra_event_count[c][RA_EVENT_LOOKAHEAD][0] / 2) / + (ra_event_count[c][RA_EVENT_LOOKAHEAD][0] + 1)); + seq_puts(s, "\n"); + + return 0; +} + +static struct dentry *readahead_dentry; + +static int ra_debug_open(struct inode *inode, struct file *file) +{ + return single_open(file, ra_account_show, NULL); +} + +static ssize_t ra_debug_write(struct file *file, const char __user *buf, + size_t size, loff_t *offset) +{ + if (file->f_dentry == readahead_dentry) + memset(ra_event_count, 0, sizeof(ra_event_count)); + return 1; +} + +static struct file_operations ra_debug_fops = { + .owner = THIS_MODULE, + .open = ra_debug_open, + .write = ra_debug_write, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static int __init readahead_init(void) +{ + readahead_dentry = debugfs_create_file("readahead", + 0644, NULL, NULL, &ra_debug_fops); + return 0; +} + +module_init(readahead_init) #define dprintk(args...) \ if (readahead_ratio & 1) printk(KERN_DEBUG args) @@ -73,6 +247,10 @@ enum ra_event { #else /* DEBUG_READAHEAD */ +static inline void ra_account(struct file_ra_state *ra, + enum ra_event e, int pages) +{ +} #define dprintk(args...) do {} while(0) #define ddprintk(args...) do {} while(0) @@ -945,6 +1123,8 @@ static int ra_dispatch(struct file_ra_st ra_account(ra, RA_EVENT_READAHEAD_EOF, actual); if (la_size) ra_account(ra, RA_EVENT_LOOKAHEAD, la_size); + if (ra_size > actual) + ra_account(ra, RA_EVENT_IO_CACHE_HIT, ra_size - actual); ra_account(ra, RA_EVENT_READAHEAD, actual); dprintk("readahead-%s(ino=%lu, index=%lu, ra=%lu+%lu-%lu) = %d\n", @@ -1577,8 +1757,11 @@ page_cache_readahead_adaptive(struct add if (page) { if(!TestClearPageReadahead(page)) return 0; - if (bdi_read_congested(mapping->backing_dev_info)) + if (bdi_read_congested(mapping->backing_dev_info)) { + ra_account(ra, RA_EVENT_IO_CONGESTION, + end_index - index); return 0; + } } if (page) @@ -1665,8 +1848,15 @@ void fastcall ra_access(struct file_ra_s (1 << PG_referenced))) return; - if (!ra_has_index(ra, page->index)) + if (ra_has_index(ra, page->index)) { + if (PageLocked(page)) + ra_account(ra, RA_EVENT_IO_BLOCK, + ra->readahead_index - page->index); + } else { + if (PageLocked(page)) + ra_account(0, RA_EVENT_IO_BLOCK, 1); return; + } ra->cache_hit++; -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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