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scsi: Optimize scsi_req_alloc

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Zeroing sense buffer for each scsi request is not efficient, we can just
leave it uninitialized because sense_len is set to 0.

Move the implicitly zeroed fields to the end of the structure and use a
partial memset.

The explicitly initialized fields (by scsi_req_alloc or scsi_req_new)
are moved to the beginning of the structure, before sense buffer, to
skip the memset.

Also change g_malloc0 to g_slice_alloc.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Fam Zheng 2014-09-16 15:20:17 +08:00 • committed by Paolo Bonzini
parent 380f649e02
commit 61e68b3fbd
2 changed files with 19 additions and 10 deletions
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21
include/hw/scsi/scsi.h
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@ -50,17 +50,24 @@ struct SCSIRequest {
uint32_t tag;
uint32_t lun;
uint32_t status;
void *hba_private;
size_t resid;
SCSICommand cmd;
/* Note:
* - fields before sense are initialized by scsi_req_alloc;
* - sense[] is uninitialized;
* - fields after sense are memset to 0 by scsi_req_alloc.
* */
uint8_t sense[SCSI_SENSE_BUF_SIZE];
uint32_t sense_len;
bool enqueued;
bool io_canceled;
bool retry;
bool dma_started;
BlockDriverAIOCB *aiocb;
QEMUSGList *sg;
bool dma_started;
uint8_t sense[SCSI_SENSE_BUF_SIZE];
uint32_t sense_len;
bool enqueued;
bool io_canceled;
bool retry;
void *hba_private;
QTAILQ_ENTRY(SCSIRequest) next;
};