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Commit 33811026 authored by Robert Elliott's avatar Robert Elliott Committed by James Bottomley
Browse files

hpsa: optimize cmd_alloc function by remembering last allocation 



Empirically, this improves performance slightly (~2% max IOPS) by
allowing cmd_alloc to remember where it left off searching for
free commands between calls instead of always starting its search
at command 0.

Reviewed-by: default avatarScott Teel <scott.teel@pmcs.com>
Signed-off-by: default avatarRobert Elliott <elliott@hp.com>
Signed-off-by: default avatarDon Brace <don.brace@pmcs.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 281a7fd0

drivers/scsi/hpsa.c

+5 −2
Original line number Original line Diff line number Diff line
@@ -4649,9 +4649,10 @@ static struct CommandList *cmd_alloc(struct ctlr_info *h) 
	union u64bit temp64;

	union u64bit temp64;

	dma_addr_t cmd_dma_handle, err_dma_handle;

	dma_addr_t cmd_dma_handle, err_dma_handle;

	int refcount;

	int refcount;

	unsigned long offset = 0;

	unsigned long offset;





	/* There is some *extremely* small but non-zero chance that that

	/*

	 * There is some *extremely* small but non-zero chance that that

	 * multiple threads could get in here, and one thread could

	 * multiple threads could get in here, and one thread could

	 * be scanning through the list of bits looking for a free

	 * be scanning through the list of bits looking for a free

	 * one, but the free ones are always behind him, and other

	 * one, but the free ones are always behind him, and other
@@ -4662,6 +4663,7 @@ static struct CommandList *cmd_alloc(struct ctlr_info *h) 
	 * infrequently as to be indistinguishable from never.

	 * infrequently as to be indistinguishable from never.

	 */

	 */





	offset = h->last_allocation; /* benignly racy */

	for (;;) {

	for (;;) {

		i = find_next_zero_bit(h->cmd_pool_bits, h->nr_cmds, offset);

		i = find_next_zero_bit(h->cmd_pool_bits, h->nr_cmds, offset);

		if (unlikely(i == h->nr_cmds)) {

		if (unlikely(i == h->nr_cmds)) {
@@ -4679,6 +4681,7 @@ static struct CommandList *cmd_alloc(struct ctlr_info *h) 
			h->cmd_pool_bits + (i / BITS_PER_LONG));

			h->cmd_pool_bits + (i / BITS_PER_LONG));

		break; /* it's ours now. */

		break; /* it's ours now. */

	}

	}

	h->last_allocation = i; /* benignly racy */





	/* Zero out all of commandlist except the last field, refcount */

	/* Zero out all of commandlist except the last field, refcount */

	memset(c, 0, offsetof(struct CommandList, refcount));

	memset(c, 0, offsetof(struct CommandList, refcount));

drivers/scsi/hpsa.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -133,6 +133,7 @@ struct ctlr_info { 
	struct CfgTable __iomem *cfgtable;

	struct CfgTable __iomem *cfgtable;

	int	interrupts_enabled;

	int	interrupts_enabled;

	int 	max_commands;

	int 	max_commands;

	int last_allocation;

	atomic_t commands_outstanding;

	atomic_t commands_outstanding;

#	define PERF_MODE_INT	0

#	define PERF_MODE_INT	0

#	define DOORBELL_INT	1

#	define DOORBELL_INT	1