Messages in this thread Patch in this message | | | Date | Sun, 4 Jun 2006 15:34:15 +0800 | From | Fengguang Wu <> | Subject | [PATCH] readahead: initial method - expected read size - fix fastcall |
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Remove 'fastcall' directive for function readahead_close().
It has drawn concerns from Andrew Morton. Now I have some benchmarks on it, and proved it as a _false_ optimization.
The tests are simple runs of the following command over _cached_ dirs: time find / > /dev/null
Table of summary(averages): user sys cpu total fastcall: 1.236 4.39 89% 6.2936 non-fastcall: 1.18 4.14166667 92% 5.75416667 stock: 1.25833333 4.14666667 93.3% 5.75866667
----------- Detailed outputs:
readahead patched kernel with fastcall: noglob find / > /dev/null 1.21s user 4.58s system 90% cpu 6.378 total noglob find / > /dev/null 1.25s user 4.47s system 86% cpu 6.623 total noglob find / > /dev/null 1.23s user 4.36s system 90% cpu 6.173 total noglob find / > /dev/null 1.25s user 4.33s system 92% cpu 6.067 total noglob find / > /dev/null 1.24s user 4.21s system 87% cpu 6.227 total
readahead patched kernel without fastcall: noglob find / > /dev/null 1.21s user 4.46s system 95% cpu 5.962 total noglob find / > /dev/null 1.26s user 4.58s system 94% cpu 6.142 total noglob find / > /dev/null 1.10s user 3.80s system 86% cpu 5.661 total noglob find / > /dev/null 1.13s user 3.98s system 95% cpu 5.355 total noglob find / > /dev/null 1.18s user 4.00s system 89% cpu 5.805 total noglob find / > /dev/null 1.22s user 4.03s system 93% cpu 5.600 total
stock kernel: noglob find / > /dev/null 1.22s user 4.24s system 94% cpu 5.803 total noglob find / > /dev/null 1.31s user 4.21s system 95% cpu 5.784 total noglob find / > /dev/null 1.27s user 4.24s system 97% cpu 5.676 total noglob find / > /dev/null 1.34s user 4.21s system 94% cpu 5.844 total noglob find / > /dev/null 1.26s user 4.08s system 89% cpu 5.935 total noglob find / > /dev/null 1.15s user 3.90s system 91% cpu 5.510 total
----------- Similar regression has also been found by Voluspa <lista1@comhem.se>: > "cd /usr ; time find . -type f -exec md5sum {} \;" > > 2.6.17-rc5 ------- 2.6.17-rc5-ar > > real 21m21.009s -- 21m37.663s > user 3m20.784s -- 3m20.701s > sys 6m34.261s -- 6m41.735s
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> ---
--- linux-2.6.17-rc5-mm2.orig/include/linux/mm.h +++ linux-2.6.17-rc5-mm2/include/linux/mm.h @@ -1068,7 +1068,7 @@ unsigned long page_cache_readahead(struc void handle_ra_miss(struct address_space *mapping, struct file_ra_state *ra, pgoff_t offset); unsigned long max_sane_readahead(unsigned long nr); -void fastcall readahead_close(struct file *file); +void readahead_close(struct file *file); unsigned long page_cache_readahead_adaptive(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, --- linux-2.6.17-rc5-mm2.orig/mm/readahead.c +++ linux-2.6.17-rc5-mm2/mm/readahead.c @@ -1943,7 +1943,7 @@ void fastcall readahead_cache_hit(struct * The resulted `ra_expect_bytes' answers the question of: * How many pages are expected to be read on start-of-file? */ -void fastcall readahead_close(struct file *file) +void readahead_close(struct file *file) { struct inode *inode = file->f_dentry->d_inode; struct address_space *mapping = inode->i_mapping; - 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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