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Commit 642c28ab authored by David Jander's avatar David Jander Committed by Ulf Hansson
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mmc: core: Optimize case for exactly one erase-group budget 



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: default avatarDavid Jander <david@protonic.nl>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 2c6625cd

drivers/mmc/core/core.c

+34 −4
Original line number Diff line number Diff line
@@ -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;

}

include/linux/mmc/card.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */