summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorroland@purestorage.com <roland@purestorage.com>2012-01-04 15:59:58 -0800
committerNicholas Bellinger <nab@linux-iscsi.org>2012-01-18 08:29:57 +0000
commit9db9da332250dbe662995703a4dcdd692112f0c3 (patch)
treebec92f208f928e41e84cc03ff9687e35eda6a062
parent6816966a8418b980481b4dced7eddd1796b145e8 (diff)
downloadop-kernel-dev-9db9da332250dbe662995703a4dcdd692112f0c3.zip
op-kernel-dev-9db9da332250dbe662995703a4dcdd692112f0c3.tar.gz
target: Don't zero pages used for data buffers
Doing alloc_page(GFP_KERNEL | __GFP_ZERO) to get pages used for data buffers wastes a lot of CPU clearing pages that will be quickly be overwritten by the actual data. However, for emulated control commands such as INQUIRY and so on, the code does assume that the buffer is zeroed. To avoid this CPU overhead, skip the __GFP_ZERO for commands that are actually moving data, ie cmds that have SCF_SCSI_DATA_SG_IO_CDB set. Signed-off-by: Roland Dreier <roland@purestorage.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
-rw-r--r--drivers/target/target_core_transport.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index d3ddd13..289bc0f 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3516,6 +3516,7 @@ transport_generic_get_mem(struct se_cmd *cmd)
u32 length = cmd->data_length;
unsigned int nents;
struct page *page;
+ gfp_t zero_flag;
int i = 0;
nents = DIV_ROUND_UP(length, PAGE_SIZE);
@@ -3526,9 +3527,11 @@ transport_generic_get_mem(struct se_cmd *cmd)
cmd->t_data_nents = nents;
sg_init_table(cmd->t_data_sg, nents);
+ zero_flag = cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB ? 0 : __GFP_ZERO;
+
while (length) {
u32 page_len = min_t(u32, length, PAGE_SIZE);
- page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ page = alloc_page(GFP_KERNEL | zero_flag);
if (!page)
goto out;
OpenPOWER on IntegriCloud