Make page size portable by querying it at runtime (#677)

So far the parameter page size in KvikIO has been a compile-time constant (4K). On GH200, however, the page size is 64K. This PR makes it portable by querying its value at runtime.

Authors:
  - Tianyu Liu (https://github.com/kingcrimsontianyu)

Approvers:
  - https://github.com/jakirkham
  - Lawrence Mitchell (https://github.com/wence-)
  - Mads R. B. Kristensen (https://github.com/madsbk)

URL: #677

Author: kingcrimsontianyu

cpp/include/kvikio/parallel_operation.hpp

@@ -156,7 +156,7 @@ std::future<std::size_t> parallel_io(F op,
                                       decltype(devPtr_offset)>);
 
   // Single-task guard
-  if (task_size >= size || page_size >= size) {
+  if (task_size >= size || get_page_size() >= size) {
     return detail::submit_task(op, buf, size, file_offset, devPtr_offset, call_idx, nvtx_color);
   }
 

cpp/include/kvikio/utils.hpp

@@ -28,8 +28,7 @@
 
 namespace kvikio {
 
-// cuFile defines a page size to 4 KiB
-inline constexpr std::size_t page_size = 4096;
+std::size_t get_page_size();
 
 [[nodiscard]] off_t convert_size2off(std::size_t x);
 

cpp/src/utils.cpp

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <unistd.h>
 #include <cstring>
 #include <iostream>
 #include <map>
@@ -28,6 +29,12 @@
 
 namespace kvikio {
 
+std::size_t get_page_size()
+{
+  static auto const page_size = static_cast<std::size_t>(sysconf(_SC_PAGESIZE));
+  return page_size;
+}
+
 off_t convert_size2off(std::size_t x)
 {
   KVIKIO_EXPECT(x < static_cast<std::size_t>(std::numeric_limits<off_t>::max()),