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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 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 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: b859a9f3-c764-42df-440d-08dbb37718d9 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB6069.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Sep 2023 10:00:30.3851 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Wmv0qcpm4XbnD09u9BFtQQJ4fmo+YEkY/03vuy/uKAcKqPq/xcyRpfbRHga19a91zYStKQ1D/XXQBg/NxJeapA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN9PR12MB5034 From: Ben Ben-Ishay When using direct data placement (DDP) the NIC could write the payload directly into the destination buffer and constructs SKBs such that they point to this data. To skip copies when SKB data already resides in the destination buffer we check if (src == dst), and skip the copy when it's true. Signed-off-by: Ben Ben-Ishay Signed-off-by: Boris Pismenny Signed-off-by: Or Gerlitz Signed-off-by: Yoray Zack Signed-off-by: Shai Malin Signed-off-by: Aurelien Aptel Reviewed-by: Chaitanya Kulkarni --- lib/iov_iter.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 424737045b97..5d9c8c196a39 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -313,9 +313,15 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) return 0; if (user_backed_iter(i)) might_fault(); + /* + * When using direct data placement (DDP) the hardware writes + * data directly to the destination buffer, and constructs + * IOVs such that they point to this data. + * Thus, when the src == dst we skip the memcpy. + */ iterate_and_advance(i, bytes, base, len, off, copyout(base, addr + off, len), - memcpy(base, addr + off, len) + (base != addr + off) && memcpy(base, addr + off, len) ) return bytes;