[PATCH] powerpc/perf/hv-24x7: use kmem_cache instead of aligned stack allocations

Cody P Schafer
2014-05-22T22:29:37Z

Ian pointed out the use of __aligned(4096) caused rather large stack
consumption in single_24x7_request(), so use the kmem_cache
hv_page_cache (which we've already got set up for other allocations)
insead of allocating locally.

Reported-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
---
arch/powerpc/perf/hv-24x7.c | 52 ++++++++++++++++++++++++++++++++-------------
1 file changed, 37 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index e0766b8..9a7a830 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -294,7 +294,7 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
u16 lpar, u64 *res,
bool success_expected)
{
- unsigned long ret;
+ unsigned long ret = -ENOMEM;

/*
* request_buffer and result_buffer are not required to be 4k aligned,
@@ -304,7 +304,27 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
struct reqb {
struct hv_24x7_request_buffer buf;
struct hv_24x7_request req;
- } __packed __aligned(4096) request_buffer = {
+ } __packed *request_buffer;
+ struct resb {
+ struct hv_24x7_data_result_buffer buf;
+ struct hv_24x7_result res;
+ struct hv_24x7_result_element elem;
+ __be64 result;
+ } __packed *result_buffer;
+
+ BUILD_BUG_ON(sizeof(*request_buffer) > 4096);
+ BUILD_BUG_ON(sizeof(*result_buffer) > 4096);
+
+ request_buffer = kmem_cache_alloc(hv_page_cache, GFP_USER);
+
+ if (!request_buffer)
+ goto out_reqb;
+
+ result_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
+ if (!result_buffer)
+ goto out_resb;
+
+ *request_buffer = (struct reqb) {
.buf = {
.interface_version = HV_24X7_IF_VERSION_CURRENT,
.num_requests = 1,
@@ -320,28 +340,30 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
}
};

- struct resb {
- struct hv_24x7_data_result_buffer buf;
- struct hv_24x7_result res;
- struct hv_24x7_result_element elem;
- __be64 result;
- } __packed __aligned(4096) result_buffer = {};
-
ret = plpar_hcall_norets(H_GET_24X7_DATA,
- virt_to_phys(&request_buffer), sizeof(request_buffer),
- virt_to_phys(&result_buffer), sizeof(result_buffer));
+ virt_to_phys(request_buffer), sizeof(*request_buffer),
+ virt_to_phys(result_buffer), sizeof(*result_buffer));

if (ret) {
if (success_expected)
pr_err_ratelimited("hcall failed: %d %#x %#x %d => 0x%lx (%ld) detail=0x%x failing ix=%x\n",
domain, offset, ix, lpar,
ret, ret,
- result_buffer.buf.detailed_rc,
- result_buffer.buf.failing_request_ix);
- return ret;
+ result_buffer->buf.detailed_rc,
+ result_buffer->buf.failing_request_ix);
+ goto out_hcall;
}

- *res = be64_to_cpu(result_buffer.result);
+ *res = be64_to_cpu(result_buffer->result);
+ kfree(result_buffer);
+ kfree(request_buffer);
+ return ret;
+
+out_hcall:
+ kfree(result_buffer);
+out_resb:
+ kfree(request_buffer);
+out_reqb:
return ret;
}

--
1.9.3