Messages in this thread Patch in this message | | | Date | Sat, 27 May 2006 23:49:07 +0800 | From | Wu Fengguang <> | Subject | [PATCH 18/32] readahead: initial method - thrashing guard size |
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backing_dev_info.ra_thrash_bytes is dynamicly updated to be a little above the thrashing safe read-ahead size. It is used in the initial method where the thrashing threshold for the particular reader is still unknown.
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> ---
mm/readahead.c | 20 ++++++++++++++++++++ 1 files changed, 20 insertions(+)
--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c +++ linux-2.6.17-rc4-mm3/mm/readahead.c @@ -796,6 +796,22 @@ out: } /* + * Update `backing_dev_info.ra_thrash_bytes' to be a _biased_ average of + * read-ahead sizes. Which makes it an a-bit-risky(*) estimation of the + * _minimal_ read-ahead thrashing threshold on the device. + * + * (*) Note that being a bit risky can _help_ overall performance. + */ +static inline void update_ra_thrash_bytes(struct backing_dev_info *bdi, + unsigned long ra_size) +{ + ra_size <<= PAGE_CACHE_SHIFT; + bdi->ra_thrash_bytes = (bdi->ra_thrash_bytes < ra_size) ? + (ra_size + bdi->ra_thrash_bytes * 1023) / 1024: + (ra_size + bdi->ra_thrash_bytes * 7) / 8; +} + +/* * The node's accumulated aging activities. */ static unsigned long node_readahead_aging(void) @@ -1144,6 +1160,10 @@ state_based_readahead(struct address_spa if (!adjust_rala(growth_limit, &ra_size, &la_size)) return 0; + /* ra_size in its _steady_ state reflects thrashing threshold */ + if (page && ra_old + ra_old / 8 >= ra_size) + update_ra_thrash_bytes(mapping->backing_dev_info, ra_size); + ra_set_class(ra, RA_CLASS_STATE); ra_set_index(ra, index, ra->readahead_index); ra_set_size(ra, ra_size, la_size); -- - 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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