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| author | Daniel P. Berrangé <berrange@redhat.com> | 2025-06-10 13:37:01 +0100 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2025-06-12 13:40:16 -0400 |
| commit | 7eeb1d3acc175813ad3d5e824f26123e0992093a (patch) | |
| tree | bc6520979fcbd5902d2fa3a9a868ea8a2c78fd37 | |
| parent | 8b723287b84a62bb5d1a7799ef0959ca8e6c293a (diff) | |
| download | qemu-7eeb1d3acc175813ad3d5e824f26123e0992093a.zip qemu-7eeb1d3acc175813ad3d5e824f26123e0992093a.tar.gz qemu-7eeb1d3acc175813ad3d5e824f26123e0992093a.tar.bz2 | |
hw/nvme/ctrl: skip automatic zero-init of large arrays
The 'nvme_map_sgl' method has a 256 element array used for copying
data from the device. Skip the automatic zero-init of this array
to eliminate the performance overhead in the I/O hot path.
The 'segment' array will be fully initialized when reading data from
the device.
The 'nme_changed_nslist' method has a 4k byte array that is manually
initialized with memset(). The compiler ought to be intelligent
enough to turn the memset() into a static initialization operation,
and thus not duplicate the automatic zero-init. Replacing memset()
with '{}' makes it unambiguous that the array is statically initialized.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Message-id: 20250610123709.835102-24-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
| -rw-r--r-- | hw/nvme/ctrl.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c index fd93550..2200028 100644 --- a/hw/nvme/ctrl.c +++ b/hw/nvme/ctrl.c @@ -1057,7 +1057,8 @@ static uint16_t nvme_map_sgl(NvmeCtrl *n, NvmeSg *sg, NvmeSglDescriptor sgl, */ #define SEG_CHUNK_SIZE 256 - NvmeSglDescriptor segment[SEG_CHUNK_SIZE], *sgld, *last_sgld; + QEMU_UNINITIALIZED NvmeSglDescriptor segment[SEG_CHUNK_SIZE]; + NvmeSglDescriptor *sgld, *last_sgld; uint64_t nsgld; uint32_t seg_len; uint16_t status; @@ -5128,7 +5129,7 @@ static uint16_t nvme_error_info(NvmeCtrl *n, uint8_t rae, uint32_t buf_len, static uint16_t nvme_changed_nslist(NvmeCtrl *n, uint8_t rae, uint32_t buf_len, uint64_t off, NvmeRequest *req) { - uint32_t nslist[1024]; + uint32_t nslist[1024] = {}; uint32_t trans_len; int i = 0; uint32_t nsid; @@ -5138,7 +5139,6 @@ static uint16_t nvme_changed_nslist(NvmeCtrl *n, uint8_t rae, uint32_t buf_len, return NVME_INVALID_FIELD | NVME_DNR; } - memset(nslist, 0x0, sizeof(nslist)); trans_len = MIN(sizeof(nslist) - off, buf_len); while ((nsid = find_first_bit(n->changed_nsids, NVME_CHANGED_NSID_SIZE)) != |