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Commit 9a5f4020 authored by Lee Susman's avatar Lee Susman Committed by Patrick Daly
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mm: change initial readahead window size calculation 



Change the logic which determines the initial readahead window size
such that for small requests (one page) the initial window size
will be x4 the size of the original request, regardless of the
VM_MAX_READAHEAD value. This prevents a rapid ramp-up
that could be caused due to increasing VM_MAX_READAHEAD.

Change-Id: I93d59c515d7e6c6d62348790980ff7bd4f434997
Signed-off-by: default avatarLee Susman <lsusman@codeaurora.org>
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent 001f314b

mm/readahead.c

+3 −1
Original line number Diff line number Diff line
@@ -233,6 +233,8 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, 


/*

 * Set the initial window size, round to next power of 2 and square

 * Small size is not dependent on max value - only a one-page read is regarded

 * as small.

 * for small size, x 4 for medium, and x 2 for large

 * for 128k (32 page) max ra

 * 1-8 page = 32k initial, > 8 page = 128k initial
@@ -241,7 +243,7 @@ static unsigned long get_init_ra_size(unsigned long size, unsigned long max) 
{

	unsigned long newsize = roundup_pow_of_two(size);



	if (newsize <= max / 32)

	if (newsize <= 1)

		newsize = newsize * 4;

	else if (newsize <= max / 4)

		newsize = newsize * 2;