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mmc: core: Optimize case for exactly one erase-group budget

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In the (not so unlikely) case that the mmc controller timeout budget is
enough for exactly one erase-group, the simplification of allowing one
sector has an enormous performance penalty. We optimize this special case
by introducing a flag that prohibits erase-group boundary crossing, so
that we can allow trimming more than one sector at a time.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
David Jander 2015-06-23 11:43:52 +02:00 committed by Ulf Hansson
parent 2c6625cd54
commit 642c28ab86
2 changed files with 35 additions and 4 deletions
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38
drivers/mmc/core/core.c
View file

@ -2168,6 +2168,7 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
unsigned int arg)
{
unsigned int rem, to = from + nr;
int err;
if (!(card->host->caps & MMC_CAP_ERASE) ||
!(card->csd.cmdclass & CCC_ERASE))
@ -2218,6 +2219,23 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
/* 'from' and 'to' are inclusive */
to -= 1;
/*
* Special case where only one erase-group fits in the timeout budget:
* If the region crosses an erase-group boundary on this particular
* case, we will be trimming more than one erase-group which, does not
* fit in the timeout budget of the controller, so we need to split it
* and call mmc_do_erase() twice if necessary. This special case is
* identified by the card->eg_boundary flag.
*/
if ((arg & MMC_TRIM_ARGS) && (card->eg_boundary) &&
(from % card->erase_size)) {
rem = card->erase_size - (from % card->erase_size);
err = mmc_do_erase(card, from, from + rem - 1, arg);
from += rem;
if ((err) || (to <= from))
return err;
}
return mmc_do_erase(card, from, to, arg);
}
EXPORT_SYMBOL(mmc_erase);
@ -2313,16 +2331,28 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
if (!qty)
return 0;
/*
* When specifying a sector range to trim, chances are we might cross
* an erase-group boundary even if the amount of sectors is less than
* one erase-group.
* If we can only fit one erase-group in the controller timeout budget,
* we have to care that erase-group boundaries are not crossed by a
* single trim operation. We flag that special case with "eg_boundary".
* In all other cases we can just decrement qty and pretend that we
* always touch (qty + 1) erase-groups as a simple optimization.
*/
if (qty == 1)
return 1;
card->eg_boundary = 1;
else
qty--;
/* Convert qty to sectors */
if (card->erase_shift)
max_discard = --qty << card->erase_shift;
max_discard = qty << card->erase_shift;
else if (mmc_card_sd(card))
max_discard = qty;
max_discard = qty + 1;
else
max_discard = --qty * card->erase_size;
max_discard = qty * card->erase_size;
return max_discard;
}

1
include/linux/mmc/card.h
View file

@ -283,6 +283,7 @@ struct mmc_card {
unsigned int erase_size; /* erase size in sectors */
unsigned int erase_shift; /* if erase unit is power 2 */
unsigned int pref_erase; /* in sectors */
unsigned int eg_boundary; /* don't cross erase-group boundaries */
u8 erased_byte; /* value of erased bytes */
u32 raw_cid[4]; /* raw card CID */